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Overview
Comment:Merge block-redirects branch with trunk. This changes the lsm file format.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
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SHA1: 647229e983d28d6d5fcfd16d138a167f63331fd6
User & Date: dan 2013-01-28 08:56:07
Context
2013-01-31
05:27
Publish routines sqlite4_stricmp() and sqlite4_strnicmp() that do simple unicode case folding. Use these routines for all internal case-insensitive string comparisons. check-in: 19e9278b9c user: drh tags: trunk
2013-01-28
08:56
Merge block-redirects branch with trunk. This changes the lsm file format. check-in: 647229e983 user: dan tags: trunk
2013-01-26
20:18
Handle calls to lsm_work() with the nPage parameter set to not greater than zero. Remove some dead code. Leaf check-in: 520f3729b8 user: dan tags: block-redirects
2013-01-25
21:23
Fix an off-by-one error in the value data decoder logic that prevented DEFAULT VALUE from working correctly in some instances. Also fix some nearby code formatting issues. check-in: 98d35b06cd user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to lsm-test/README.

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              the system recovers and other clients proceed unaffected if
              a process fails in the middle of a write transaction.

              The difference from lsmtest2.c is that this file tests
              live-recovery (recovery from a failure that occurs while other
              clients are still running) whereas lsmtest2.c tests recovery
              from a system or power failure.
















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              the system recovers and other clients proceed unaffected if
              a process fails in the middle of a write transaction.

              The difference from lsmtest2.c is that this file tests
              live-recovery (recovery from a failure that occurs while other
              clients are still running) whereas lsmtest2.c tests recovery
              from a system or power failure.

  lsmtest9.c: More data tests. These focus on testing that calling
              lsm_work(nMerge=1) to compact the database does not corrupt it.
              In other words, that databases containing block-redirects
              can be read and written.




Changes to lsm-test/lsmtest.h.

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void test_data_1(const char *, const char *, int *pRc);
void test_data_2(const char *, const char *, int *pRc);
void test_data_3(const char *, const char *, int *pRc);
void testDbContents(TestDb *, Datasource *, int, int, int, int, int, int *);
void testCaseProgress(int, int, int, int *);
int testCaseNDot(void);




typedef struct CksumDb CksumDb;
CksumDb *testCksumArrayNew(Datasource *, int, int, int);
char *testCksumArrayGet(CksumDb *, int);
void testCksumArrayFree(CksumDb *);
void testCaseStart(int *pRc, char *zFmt, ...);
void testCaseFinish(int rc);
void testCaseSkip(void);
................................................................................

#define TEST_CKSUM_BYTES 29
int testCksumDatabase(TestDb *pDb, char *zOut);
int testCountDatabase(TestDb *pDb);
void testCompareInt(int, int, int *);
void testCompareStr(const char *z1, const char *z2, int *pRc);





/*
** Similar to the Tcl_GetIndexFromObjStruct() Tcl library function.
*/
#define testArgSelect(w,x,y,z) testArgSelectX(w,x,sizeof(w[0]),y,z)
int testArgSelectX(void *, const char *, int, const char *, int *);

#ifdef __cplusplus
}  /* End of the 'extern "C"' block */
#endif

#endif







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void test_data_1(const char *, const char *, int *pRc);
void test_data_2(const char *, const char *, int *pRc);
void test_data_3(const char *, const char *, int *pRc);
void testDbContents(TestDb *, Datasource *, int, int, int, int, int, int *);
void testCaseProgress(int, int, int, int *);
int testCaseNDot(void);

void testCompareDb(Datasource *, int, int, TestDb *, TestDb *, int *);
int testControlDb(TestDb **ppDb);

typedef struct CksumDb CksumDb;
CksumDb *testCksumArrayNew(Datasource *, int, int, int);
char *testCksumArrayGet(CksumDb *, int);
void testCksumArrayFree(CksumDb *);
void testCaseStart(int *pRc, char *zFmt, ...);
void testCaseFinish(int rc);
void testCaseSkip(void);
................................................................................

#define TEST_CKSUM_BYTES 29
int testCksumDatabase(TestDb *pDb, char *zOut);
int testCountDatabase(TestDb *pDb);
void testCompareInt(int, int, int *);
void testCompareStr(const char *z1, const char *z2, int *pRc);

/* lsmtest9.c */
void test_data_4(const char *, const char *, int *pRc);


/*
** Similar to the Tcl_GetIndexFromObjStruct() Tcl library function.
*/
#define testArgSelect(w,x,y,z) testArgSelectX(w,x,sizeof(w[0]),y,z)
int testArgSelectX(void *, const char *, int, const char *, int *);

#ifdef __cplusplus
}  /* End of the 'extern "C"' block */
#endif

#endif

Changes to lsm-test/lsmtest1.c.

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  zRet = testMallocPrintf("data.%s.%s.%d.%d", 
      zSystem, zData, pTest->nRow, pTest->nVerify
  );
  testFree(zData);
  return zRet;
}

static int testControlDb(TestDb **ppDb){
#ifdef HAVE_KYOTOCABINET
  return tdb_open("kyotocabinet", "tmp.db", 1, ppDb);
#else
  return tdb_open("sqlite3", ":memory:", 1, ppDb);
#endif
}

................................................................................
    if( testCaseBegin(pRc, zPattern, "%s", zName) ){
      doDataTest1(zSystem, &aTest[i], pRc);
    }
    testFree(zName);
  }
}

static void testCompareDb(
  Datasource *pData,
  int nData,
  int iSeed,
  TestDb *pControl,
  TestDb *pDb,
  int *pRc
){







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  zRet = testMallocPrintf("data.%s.%s.%d.%d", 
      zSystem, zData, pTest->nRow, pTest->nVerify
  );
  testFree(zData);
  return zRet;
}

int testControlDb(TestDb **ppDb){
#ifdef HAVE_KYOTOCABINET
  return tdb_open("kyotocabinet", "tmp.db", 1, ppDb);
#else
  return tdb_open("sqlite3", ":memory:", 1, ppDb);
#endif
}

................................................................................
    if( testCaseBegin(pRc, zPattern, "%s", zName) ){
      doDataTest1(zSystem, &aTest[i], pRc);
    }
    testFree(zName);
  }
}

void testCompareDb(
  Datasource *pData,
  int nData,
  int iSeed,
  TestDb *pControl,
  TestDb *pDb,
  int *pRc
){

Added lsm-test/lsmtest9.c.





















































































































































































































































































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#include "lsmtest.h"

#define DATA_SEQUENTIAL TEST_DATASOURCE_SEQUENCE
#define DATA_RANDOM     TEST_DATASOURCE_RANDOM

typedef struct Datatest4 Datatest4;

/*
** Test overview:
**
**   1. Insert (Datatest4.nRec) records into a database.
**
**   2. Repeat (Datatest4.nRepeat) times:
**
**      2a. Delete 2/3 of the records in the database.
**
**      2b. Run lsm_work(nMerge=1).
**
**      2c. Insert as many records as were deleted in 2a.
**
**      2d. Check database content is as expected.
**
**      2e. If (Datatest4.bReopen) is true, close and reopen the database.
*/
struct Datatest4 {
  /* Datasource definition */
  DatasourceDefn defn;

  int nRec;
  int nRepeat;
  int bReopen;
};

static void doDataTest4(
  const char *zSystem,            /* Database system to test */
  Datatest4 *p,                   /* Structure containing test parameters */
  int *pRc                        /* OUT: Error code */
){
  lsm_db *db = 0;
  TestDb *pDb;
  TestDb *pControl;
  Datasource *pData;
  int i;
  int rc = 0;
  int iDot = 0;

  int nRecOn3 = (p->nRec / 3);
  int iData = 0;

  /* Start the test case, open a database and allocate the datasource. */
  rc = testControlDb(&pControl);
  pDb = testOpen(zSystem, 1, &rc);
  pData = testDatasourceNew(&p->defn);
  if( rc==0 ) db = tdb_lsm(pDb);

  testWriteDatasourceRange(pControl, pData, iData, nRecOn3*3, &rc);
  testWriteDatasourceRange(pDb,      pData, iData, nRecOn3*3, &rc);

  for(i=0; rc==0 && i<p->nRepeat; i++){

    testDeleteDatasourceRange(pControl, pData, iData, nRecOn3*2, &rc);
    testDeleteDatasourceRange(pDb,      pData, iData, nRecOn3*2, &rc);

    if( db ){
      int nDone;
#if 0
      fprintf(stderr, "lsm_work() start...\n"); fflush(stderr);
#endif
      do {
        nDone = 0;
        rc = lsm_work(db, 1, (1<<30), &nDone);
      }while( rc==0 && nDone>0 );
#if 0 
      fprintf(stderr, "lsm_work() done...\n"); fflush(stderr);
#endif
    }

if( i+1<p->nRepeat ){
    iData += (nRecOn3*2);
    testWriteDatasourceRange(pControl, pData, iData+nRecOn3, nRecOn3*2, &rc);
    testWriteDatasourceRange(pDb,      pData, iData+nRecOn3, nRecOn3*2, &rc);

    testCompareDb(pData, nRecOn3*3, iData, pControl, pDb, &rc);

    /* If Datatest4.bReopen is true, close and reopen the database */
    if( p->bReopen ){
      testReopen(&pDb, &rc);
      if( rc==0 ) db = tdb_lsm(pDb);
    }
}

    /* Update the progress dots... */
    testCaseProgress(i, p->nRepeat, testCaseNDot(), &iDot);
  }

  testClose(&pDb);
  testClose(&pControl);
  testDatasourceFree(pData);
  testCaseFinish(rc);
  *pRc = rc;
}

static char *getName4(const char *zSystem, Datatest4 *pTest){
  char *zRet;
  char *zData;
  zData = testDatasourceName(&pTest->defn);
  zRet = testMallocPrintf("data4.%s.%s.%d.%d.%d", 
      zSystem, zData, pTest->nRec, pTest->nRepeat, pTest->bReopen
  );
  testFree(zData);
  return zRet;
}

void test_data_4(
  const char *zSystem,            /* Database system name */
  const char *zPattern,           /* Run test cases that match this pattern */
  int *pRc                        /* IN/OUT: Error code */
){
  Datatest4 aTest[] = {
      /* defn,                                 nRec, nRepeat, bReopen */
    { {DATA_RANDOM,     20,25,     500,600}, 10000,      10,       0   },
    { {DATA_RANDOM,     20,25,     500,600}, 10000,      10,       1   },
  };

  int i;

  for(i=0; *pRc==LSM_OK && i<ArraySize(aTest); i++){
    char *zName = getName4(zSystem, &aTest[i]);
    if( testCaseBegin(pRc, zPattern, "%s", zName) ){
      doDataTest4(zSystem, &aTest[i], pRc);
    }
    testFree(zName);
  }
}



Changes to lsm-test/lsmtest_func.c.

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  if( rc!=LSM_OK ){
    testPrintError("lsm_open(): rc=%d\n", rc);
  }else{
    rc = lsm_open(pDb, zDb);
    if( rc!=LSM_OK ){
      testPrintError("lsm_open(): rc=%d\n", rc);
    }else{





      rc = lsm_work(pDb, nMerge, nWork, 0);
      if( rc!=LSM_OK ){
        testPrintError("lsm_work(): rc=%d\n", rc);
      }
    }
  }
  if( rc==LSM_OK ){







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  if( rc!=LSM_OK ){
    testPrintError("lsm_open(): rc=%d\n", rc);
  }else{
    rc = lsm_open(pDb, zDb);
    if( rc!=LSM_OK ){
      testPrintError("lsm_open(): rc=%d\n", rc);
    }else{
      int n = -1;
      lsm_config(pDb, LSM_CONFIG_BLOCK_SIZE, &n);
      n = n*2;
      lsm_config(pDb, LSM_CONFIG_AUTOCHECKPOINT, &n);

      rc = lsm_work(pDb, nMerge, nWork, 0);
      if( rc!=LSM_OK ){
        testPrintError("lsm_work(): rc=%d\n", rc);
      }
    }
  }
  if( rc==LSM_OK ){

Changes to lsm-test/lsmtest_main.c.

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  for(j=0; tdb_system_name(j); j++){
    rc = 0;

    test_data_1(tdb_system_name(j), zPattern, &rc);
    test_data_2(tdb_system_name(j), zPattern, &rc);
    test_data_3(tdb_system_name(j), zPattern, &rc);

    test_rollback(tdb_system_name(j), zPattern, &rc);
    test_mc(tdb_system_name(j), zPattern, &rc);
    test_mt(tdb_system_name(j), zPattern, &rc);

    if( rc ) nFail++;
  }








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  for(j=0; tdb_system_name(j); j++){
    rc = 0;

    test_data_1(tdb_system_name(j), zPattern, &rc);
    test_data_2(tdb_system_name(j), zPattern, &rc);
    test_data_3(tdb_system_name(j), zPattern, &rc);
    test_data_4(tdb_system_name(j), zPattern, &rc);
    test_rollback(tdb_system_name(j), zPattern, &rc);
    test_mc(tdb_system_name(j), zPattern, &rc);
    test_mt(tdb_system_name(j), zPattern, &rc);

    if( rc ) nFail++;
  }

Changes to lsm-test/lsmtest_tdb3.c.

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}

int test_lsm_lomem_open(
  const char *zFilename, 
  int bClear, 
  TestDb **ppDb
){

  const char *zCfg = 
    "page_size=256 block_size=65536 autoflush=16384 "
    "max_freelist=2 autocheckpoint=32768 "
    "mmap=0 "
  ;
  return testLsmOpen(zCfg, zFilename, bClear, ppDb);
}

int test_lsm_zip_open(
  const char *zFilename, 
  int bClear, 
  TestDb **ppDb
){
  const char *zCfg = 
    "page_size=256 block_size=65536 autoflush=16384 "
    "max_freelist=2 autocheckpoint=32768 compression=1"
    "mmap=0 "
  ;
  return testLsmOpen(zCfg, zFilename, bClear, ppDb);
}

lsm_db *tdb_lsm(TestDb *pDb){
  if( pDb->pMethods->xClose==test_lsm_close ){
    return ((LsmDb *)pDb)->db;







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int test_lsm_lomem_open(
  const char *zFilename, 
  int bClear, 
  TestDb **ppDb
){
    /* "max_freelist=4 autocheckpoint=32768 " */
  const char *zCfg = 
    "page_size=256 block_size=65536 autoflush=16384 "
    "autocheckpoint=32768 "
    "mmap=0 "
  ;
  return testLsmOpen(zCfg, zFilename, bClear, ppDb);
}

int test_lsm_zip_open(
  const char *zFilename, 
  int bClear, 
  TestDb **ppDb
){
  const char *zCfg = 
    "page_size=256 block_size=65536 autoflush=16384 "
    "autocheckpoint=32768 compression=1 mmap=0 "

  ;
  return testLsmOpen(zCfg, zFilename, bClear, ppDb);
}

lsm_db *tdb_lsm(TestDb *pDb){
  if( pDb->pMethods->xClose==test_lsm_close ){
    return ((LsmDb *)pDb)->db;

Changes to main.mk.

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EXTHDR += \
  $(TOP)/ext/icu/sqliteicu.h

LSMTESTSRC = $(TOP)/lsm-test/lsmtest1.c $(TOP)/lsm-test/lsmtest2.c           \
             $(TOP)/lsm-test/lsmtest3.c $(TOP)/lsm-test/lsmtest4.c           \
             $(TOP)/lsm-test/lsmtest5.c $(TOP)/lsm-test/lsmtest6.c           \
             $(TOP)/lsm-test/lsmtest7.c $(TOP)/lsm-test/lsmtest8.c           \

             $(TOP)/lsm-test/lsmtest_datasource.c \
             $(TOP)/lsm-test/lsmtest_func.c $(TOP)/lsm-test/lsmtest_io.c     \
             $(TOP)/lsm-test/lsmtest_main.c $(TOP)/lsm-test/lsmtest_mem.c    \
             $(TOP)/lsm-test/lsmtest_tdb.c $(TOP)/lsm-test/lsmtest_tdb3.c    \
             $(TOP)/lsm-test/lsmtest_util.c 

LSMTESTHDR = $(TOP)/lsm-test/lsmtest.h $(TOP)/lsm-test/lsmtest_tdb.h







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EXTHDR += \
  $(TOP)/ext/icu/sqliteicu.h

LSMTESTSRC = $(TOP)/lsm-test/lsmtest1.c $(TOP)/lsm-test/lsmtest2.c           \
             $(TOP)/lsm-test/lsmtest3.c $(TOP)/lsm-test/lsmtest4.c           \
             $(TOP)/lsm-test/lsmtest5.c $(TOP)/lsm-test/lsmtest6.c           \
             $(TOP)/lsm-test/lsmtest7.c $(TOP)/lsm-test/lsmtest8.c           \
             $(TOP)/lsm-test/lsmtest9.c                                      \
             $(TOP)/lsm-test/lsmtest_datasource.c \
             $(TOP)/lsm-test/lsmtest_func.c $(TOP)/lsm-test/lsmtest_io.c     \
             $(TOP)/lsm-test/lsmtest_main.c $(TOP)/lsm-test/lsmtest_mem.c    \
             $(TOP)/lsm-test/lsmtest_tdb.c $(TOP)/lsm-test/lsmtest_tdb3.c    \
             $(TOP)/lsm-test/lsmtest_util.c 

LSMTESTHDR = $(TOP)/lsm-test/lsmtest.h $(TOP)/lsm-test/lsmtest_tdb.h

Changes to src/lsmInt.h.

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typedef struct LsmString LsmString;
typedef struct Mempool Mempool;
typedef struct Merge Merge;
typedef struct MergeInput MergeInput;
typedef struct MetaPage MetaPage;
typedef struct MultiCursor MultiCursor;
typedef struct Page Page;

typedef struct Segment Segment;
typedef struct SegmentMerger SegmentMerger;
typedef struct ShmChunk ShmChunk;
typedef struct ShmHeader ShmHeader;
typedef struct ShmReader ShmReader;
typedef struct Snapshot Snapshot;
typedef struct TransMark TransMark;
................................................................................

/*
** Hard limit on the number of free-list entries that may be stored in 
** a checkpoint (the remainder are stored as a system record in the LSM).
** See also LSM_CONFIG_MAX_FREELIST.
*/
#define LSM_MAX_FREELIST_ENTRIES 24



#define LSM_ATTEMPTS_BEFORE_PROTOCOL 10000


/*
** Each entry stored in the LSM (or in-memory tree structure) has an
** associated mask of the following flags.
................................................................................
*/
typedef struct IntArray IntArray;
struct IntArray {
  int nAlloc;
  int nArray;
  u32 *aArray;
};









/*
** An instance of this structure represents a point in the history of the
** tree structure to roll back to. Refer to comments in lsm_tree.c for 
** details.
*/
struct TreeMark {
................................................................................
  lsm_compress compress;          /* Compression callbacks */

  /* Sub-system handles */
  FileSystem *pFS;                /* On-disk portion of database */
  Database *pDatabase;            /* Database shared data */

  /* Client transaction context */
  Snapshot *pClient;              /* Client snapshot (non-NULL in read trans) */
  int iReader;                    /* Read lock held (-1 == unlocked) */
  MultiCursor *pCsr;              /* List of all open cursors */
  LogWriter *pLogWriter;          /* Context for writing to the log file */
  int nTransOpen;                 /* Number of opened write transactions */
  int nTransAlloc;                /* Allocated size of aTrans[] array */
  TransMark *aTrans;              /* Array of marks for transaction rollback */
  IntArray rollback;              /* List of tree-nodes to roll back */

  /* Worker context */
  Snapshot *pWorker;              /* Worker snapshot (or NULL) */
  Freelist *pFreelist;            /* See sortedNewToplevel() */
  int bUseFreelist;               /* True to use pFreelist */


  /* Debugging message callback */
  void (*xLog)(void *, int, const char *);
  void *pLogCtx;

  /* Work done notification callback */
  void (*xWork)(lsm_db *, void *);
................................................................................
};

struct Segment {
  Pgno iFirst;                     /* First page of this run */
  Pgno iLastPg;                    /* Last page of this run */
  Pgno iRoot;                      /* Root page number (if any) */
  int nSize;                       /* Size of this run in pages */


};

/*
** iSplitTopic/pSplitKey/nSplitKey:
**   If nRight>0, this buffer contains a copy of the largest key that has
**   already been written to the left-hand-side of the level.
*/
................................................................................
** Database below for futher details.
*/
struct Snapshot {
  Database *pDatabase;            /* Database this snapshot belongs to */
  Level *pLevel;                  /* Pointer to level 0 of snapshot (or NULL) */
  i64 iId;                        /* Snapshot id */
  i64 iLogOff;                    /* Log file offset */


  /* Used by worker snapshots only */
  int nBlock;                     /* Number of blocks in database file */
  Pgno aiAppend[LSM_APPLIST_SZ];  /* Append point list */
  Freelist freelist;              /* Free block list */
  u32 nWrite;                     /* Total number of pages written to disk */
};
................................................................................

int lsmFsSectorSize(FileSystem *);

void lsmSortedSplitkey(lsm_db *, Level *, int *);

/* Reading sorted run content. */
int lsmFsDbPageLast(FileSystem *pFS, Segment *pSeg, Page **ppPg);
int lsmFsDbPageGet(FileSystem *, Pgno, Page **);
int lsmFsDbPageNext(Segment *, Page *, int eDir, Page **);

u8 *lsmFsPageData(Page *, int *);
int lsmFsPageRelease(Page *);
int lsmFsPagePersist(Page *);
void lsmFsPageRef(Page *);
Pgno lsmFsPageNumber(Page *);
................................................................................
int lsmEnvShmMap(lsm_env *, lsm_file *, int, int, void **); 
void lsmEnvShmBarrier(lsm_env *);
void lsmEnvShmUnmap(lsm_env *, lsm_file *, int);

void lsmEnvSleep(lsm_env *, int);

int lsmFsReadSyncedId(lsm_db *db, int, i64 *piVal);




/*
** End of functions from "lsm_file.c".
**************************************************************************/

/* 
** Functions from file "lsm_sorted.c".
................................................................................
void lsmSnapshotSetCkptid(Snapshot *, i64);

Level *lsmDbSnapshotLevel(Snapshot *);
void lsmDbSnapshotSetLevel(Snapshot *, Level *);

void lsmDbRecoveryComplete(lsm_db *, int);

int lsmBlockAllocate(lsm_db *, int *);
int lsmBlockFree(lsm_db *, int);
int lsmBlockRefree(lsm_db *, int);

void lsmFreelistDeltaBegin(lsm_db *);
void lsmFreelistDeltaEnd(lsm_db *);
int lsmFreelistDelta(lsm_db *pDb);








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typedef struct LsmString LsmString;
typedef struct Mempool Mempool;
typedef struct Merge Merge;
typedef struct MergeInput MergeInput;
typedef struct MetaPage MetaPage;
typedef struct MultiCursor MultiCursor;
typedef struct Page Page;
typedef struct Redirect Redirect;
typedef struct Segment Segment;
typedef struct SegmentMerger SegmentMerger;
typedef struct ShmChunk ShmChunk;
typedef struct ShmHeader ShmHeader;
typedef struct ShmReader ShmReader;
typedef struct Snapshot Snapshot;
typedef struct TransMark TransMark;
................................................................................

/*
** Hard limit on the number of free-list entries that may be stored in 
** a checkpoint (the remainder are stored as a system record in the LSM).
** See also LSM_CONFIG_MAX_FREELIST.
*/
#define LSM_MAX_FREELIST_ENTRIES 24

#define LSM_MAX_BLOCK_REDIRECTS 16

#define LSM_ATTEMPTS_BEFORE_PROTOCOL 10000


/*
** Each entry stored in the LSM (or in-memory tree structure) has an
** associated mask of the following flags.
................................................................................
*/
typedef struct IntArray IntArray;
struct IntArray {
  int nAlloc;
  int nArray;
  u32 *aArray;
};

struct Redirect {
  int n;                          /* Number of redirects */
  struct RedirectEntry {
    int iFrom;
    int iTo;
  } *a;
};

/*
** An instance of this structure represents a point in the history of the
** tree structure to roll back to. Refer to comments in lsm_tree.c for 
** details.
*/
struct TreeMark {
................................................................................
  lsm_compress compress;          /* Compression callbacks */

  /* Sub-system handles */
  FileSystem *pFS;                /* On-disk portion of database */
  Database *pDatabase;            /* Database shared data */

  /* Client transaction context */
  Snapshot *pClient;              /* Client snapshot */
  int iReader;                    /* Read lock held (-1 == unlocked) */
  MultiCursor *pCsr;              /* List of all open cursors */
  LogWriter *pLogWriter;          /* Context for writing to the log file */
  int nTransOpen;                 /* Number of opened write transactions */
  int nTransAlloc;                /* Allocated size of aTrans[] array */
  TransMark *aTrans;              /* Array of marks for transaction rollback */
  IntArray rollback;              /* List of tree-nodes to roll back */

  /* Worker context */
  Snapshot *pWorker;              /* Worker snapshot (or NULL) */
  Freelist *pFreelist;            /* See sortedNewToplevel() */
  int bUseFreelist;               /* True to use pFreelist */
  int bIncrMerge;                 /* True if currently doing a merge */

  /* Debugging message callback */
  void (*xLog)(void *, int, const char *);
  void *pLogCtx;

  /* Work done notification callback */
  void (*xWork)(lsm_db *, void *);
................................................................................
};

struct Segment {
  Pgno iFirst;                     /* First page of this run */
  Pgno iLastPg;                    /* Last page of this run */
  Pgno iRoot;                      /* Root page number (if any) */
  int nSize;                       /* Size of this run in pages */

  Redirect *pRedirect;             /* Block redirects (or NULL) */
};

/*
** iSplitTopic/pSplitKey/nSplitKey:
**   If nRight>0, this buffer contains a copy of the largest key that has
**   already been written to the left-hand-side of the level.
*/
................................................................................
** Database below for futher details.
*/
struct Snapshot {
  Database *pDatabase;            /* Database this snapshot belongs to */
  Level *pLevel;                  /* Pointer to level 0 of snapshot (or NULL) */
  i64 iId;                        /* Snapshot id */
  i64 iLogOff;                    /* Log file offset */
  Redirect redirect;              /* Block redirection array */

  /* Used by worker snapshots only */
  int nBlock;                     /* Number of blocks in database file */
  Pgno aiAppend[LSM_APPLIST_SZ];  /* Append point list */
  Freelist freelist;              /* Free block list */
  u32 nWrite;                     /* Total number of pages written to disk */
};
................................................................................

int lsmFsSectorSize(FileSystem *);

void lsmSortedSplitkey(lsm_db *, Level *, int *);

/* Reading sorted run content. */
int lsmFsDbPageLast(FileSystem *pFS, Segment *pSeg, Page **ppPg);
int lsmFsDbPageGet(FileSystem *, Segment *, Pgno, Page **);
int lsmFsDbPageNext(Segment *, Page *, int eDir, Page **);

u8 *lsmFsPageData(Page *, int *);
int lsmFsPageRelease(Page *);
int lsmFsPagePersist(Page *);
void lsmFsPageRef(Page *);
Pgno lsmFsPageNumber(Page *);
................................................................................
int lsmEnvShmMap(lsm_env *, lsm_file *, int, int, void **); 
void lsmEnvShmBarrier(lsm_env *);
void lsmEnvShmUnmap(lsm_env *, lsm_file *, int);

void lsmEnvSleep(lsm_env *, int);

int lsmFsReadSyncedId(lsm_db *db, int, i64 *piVal);

int lsmFsSegmentContainsPg(FileSystem *pFS, Segment *, Pgno, int *);
Pgno lsmFsRedirectPage(FileSystem *, Redirect *, Pgno);

/*
** End of functions from "lsm_file.c".
**************************************************************************/

/* 
** Functions from file "lsm_sorted.c".
................................................................................
void lsmSnapshotSetCkptid(Snapshot *, i64);

Level *lsmDbSnapshotLevel(Snapshot *);
void lsmDbSnapshotSetLevel(Snapshot *, Level *);

void lsmDbRecoveryComplete(lsm_db *, int);

int lsmBlockAllocate(lsm_db *, int, int *);
int lsmBlockFree(lsm_db *, int);
int lsmBlockRefree(lsm_db *, int);

void lsmFreelistDeltaBegin(lsm_db *);
void lsmFreelistDeltaEnd(lsm_db *);
int lsmFreelistDelta(lsm_db *pDb);

Changes to src/lsm_ckpt.c.

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**     6. For each segment in the merge:
**        5a. Page number of next cell to read during merge (this field
**            is 64-bits - 2 integers)
**        5b. Cell number of next cell to read during merge
**     7. Page containing current split-key (64-bits - 2 integers).
**     8. Cell within page containing current split-key.
**     9. Current pointer value (64-bits - 2 integers).







**
**   The in-memory freelist entries. Each entry is either an insert or a
**   delete. The in-memory freelist is to the free-block-list as the
**   in-memory tree is to the users database content.
**
**     1. Number of free-list entries stored in checkpoint header.
**     2. Number of free blocks (in total).
................................................................................

  /* Serialize nLevel levels. */
  iLevel = 0;
  for(pLevel=lsmDbSnapshotLevel(pSnap); iLevel<nLevel; pLevel=pLevel->pNext){
    ckptExportLevel(pLevel, &ckpt, &iOut, &rc);
    iLevel++;
  }








  /* Write the freelist */
  assert( pSnap->freelist.nEntry<=pDb->nMaxFreelist );
  if( rc==LSM_OK ){
    int nFree = pSnap->freelist.nEntry;
    ckptSetValue(&ckpt, iOut++, nFree, &rc);
    for(i=0; i<nFree; i++){
................................................................................
      return LSM_PROTOCOL;
    }
  }

  rc = lsmCheckpointDeserialize(pDb, 1, pShm->aSnap1, &pDb->pWorker);
  if( pDb->pWorker ) pDb->pWorker->pDatabase = pDb->pDatabase;


  assert( rc!=LSM_OK || lsmFsIntegrityCheck(pDb) );

  return rc;
}

int lsmCheckpointDeserialize(
  lsm_db *pDb, 
  int bInclFreelist,              /* If true, deserialize free-list */
  u32 *aCkpt, 
................................................................................
  Snapshot **ppSnap
){
  int rc = LSM_OK;
  Snapshot *pNew;

  pNew = (Snapshot *)lsmMallocZeroRc(pDb->pEnv, sizeof(Snapshot), &rc);
  if( rc==LSM_OK ){

    int nFree;
    int i;
    int nLevel = (int)aCkpt[CKPT_HDR_NLEVEL];
    int iIn = CKPT_HDR_SIZE + CKPT_APPENDLIST_SIZE + CKPT_LOGPTR_SIZE;

    pNew->iId = lsmCheckpointId(aCkpt, 0);
    pNew->nBlock = aCkpt[CKPT_HDR_NBLOCK];
................................................................................
    pNew->iLogOff = lsmCheckpointLogOffset(aCkpt);

    /* Make a copy of the append-list */
    for(i=0; i<LSM_APPLIST_SZ; i++){
      u32 *a = &aCkpt[CKPT_HDR_SIZE + CKPT_LOGPTR_SIZE + i*2];
      pNew->aiAppend[i] = ckptRead64(a);
    }





















    /* Copy the free-list */
    if( bInclFreelist ){
      nFree = aCkpt[iIn++];
      if( nFree ){
        pNew->freelist.aEntry = (FreelistEntry *)lsmMallocZeroRc(
            pDb->pEnv, sizeof(FreelistEntry)*nFree, &rc
        );
        if( rc==LSM_OK ){
          int i;
................................................................................
int lsmCheckpointSaveWorker(lsm_db *pDb, int bFlush){
  Snapshot *pSnap = pDb->pWorker;
  ShmHeader *pShm = pDb->pShmhdr;
  void *p = 0;
  int n = 0;
  int rc;


  rc = ckptExportSnapshot(pDb, bFlush, pSnap->iId+1, 1, &p, &n);
  if( rc!=LSM_OK ) return rc;
  assert( ckptChecksumOk((u32 *)p) );

  assert( n<=LSM_META_PAGE_SIZE );
  memcpy(pShm->aSnap2, p, n);
  lsmShmBarrier(pDb);
  memcpy(pShm->aSnap1, p, n);







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**     6. For each segment in the merge:
**        5a. Page number of next cell to read during merge (this field
**            is 64-bits - 2 integers)
**        5b. Cell number of next cell to read during merge
**     7. Page containing current split-key (64-bits - 2 integers).
**     8. Cell within page containing current split-key.
**     9. Current pointer value (64-bits - 2 integers).
**
**   The block redirect array:
**
**     1. Number of redirections (maximum LSM_MAX_BLOCK_REDIRECTS).
**     2. For each redirection:
**        a. "from" block number
**        b. "to" block number
**
**   The in-memory freelist entries. Each entry is either an insert or a
**   delete. The in-memory freelist is to the free-block-list as the
**   in-memory tree is to the users database content.
**
**     1. Number of free-list entries stored in checkpoint header.
**     2. Number of free blocks (in total).
................................................................................

  /* Serialize nLevel levels. */
  iLevel = 0;
  for(pLevel=lsmDbSnapshotLevel(pSnap); iLevel<nLevel; pLevel=pLevel->pNext){
    ckptExportLevel(pLevel, &ckpt, &iOut, &rc);
    iLevel++;
  }

  /* Write the block-redirect list */
  ckptSetValue(&ckpt, iOut++, pSnap->redirect.n, &rc);
  for(i=0; i<pSnap->redirect.n; i++){
    ckptSetValue(&ckpt, iOut++, pSnap->redirect.a[i].iFrom, &rc);
    ckptSetValue(&ckpt, iOut++, pSnap->redirect.a[i].iTo, &rc);
  }

  /* Write the freelist */
  assert( pSnap->freelist.nEntry<=pDb->nMaxFreelist );
  if( rc==LSM_OK ){
    int nFree = pSnap->freelist.nEntry;
    ckptSetValue(&ckpt, iOut++, nFree, &rc);
    for(i=0; i<nFree; i++){
................................................................................
      return LSM_PROTOCOL;
    }
  }

  rc = lsmCheckpointDeserialize(pDb, 1, pShm->aSnap1, &pDb->pWorker);
  if( pDb->pWorker ) pDb->pWorker->pDatabase = pDb->pDatabase;

#if 0
  assert( rc!=LSM_OK || lsmFsIntegrityCheck(pDb) );
#endif
  return rc;
}

int lsmCheckpointDeserialize(
  lsm_db *pDb, 
  int bInclFreelist,              /* If true, deserialize free-list */
  u32 *aCkpt, 
................................................................................
  Snapshot **ppSnap
){
  int rc = LSM_OK;
  Snapshot *pNew;

  pNew = (Snapshot *)lsmMallocZeroRc(pDb->pEnv, sizeof(Snapshot), &rc);
  if( rc==LSM_OK ){
    Level *pLvl;
    int nFree;
    int i;
    int nLevel = (int)aCkpt[CKPT_HDR_NLEVEL];
    int iIn = CKPT_HDR_SIZE + CKPT_APPENDLIST_SIZE + CKPT_LOGPTR_SIZE;

    pNew->iId = lsmCheckpointId(aCkpt, 0);
    pNew->nBlock = aCkpt[CKPT_HDR_NBLOCK];
................................................................................
    pNew->iLogOff = lsmCheckpointLogOffset(aCkpt);

    /* Make a copy of the append-list */
    for(i=0; i<LSM_APPLIST_SZ; i++){
      u32 *a = &aCkpt[CKPT_HDR_SIZE + CKPT_LOGPTR_SIZE + i*2];
      pNew->aiAppend[i] = ckptRead64(a);
    }

    /* Read the block-redirect list */
    pNew->redirect.n = aCkpt[iIn++];
    if( pNew->redirect.n ){
      pNew->redirect.a = lsmMallocZeroRc(pDb->pEnv, 
          (sizeof(struct RedirectEntry) * LSM_MAX_BLOCK_REDIRECTS), &rc
      );
      if( rc==LSM_OK ){
        for(i=0; i<pNew->redirect.n; i++){
          pNew->redirect.a[i].iFrom = aCkpt[iIn++];
          pNew->redirect.a[i].iTo = aCkpt[iIn++];
        }
      }
      for(pLvl=pNew->pLevel; pLvl->pNext; pLvl=pLvl->pNext);
      if( pLvl->nRight ){
        pLvl->aRhs[pLvl->nRight-1].pRedirect = &pNew->redirect;
      }else{
        pLvl->lhs.pRedirect = &pNew->redirect;
      }
    }

    /* Copy the free-list */
    if( rc==LSM_OK && bInclFreelist ){
      nFree = aCkpt[iIn++];
      if( nFree ){
        pNew->freelist.aEntry = (FreelistEntry *)lsmMallocZeroRc(
            pDb->pEnv, sizeof(FreelistEntry)*nFree, &rc
        );
        if( rc==LSM_OK ){
          int i;
................................................................................
int lsmCheckpointSaveWorker(lsm_db *pDb, int bFlush){
  Snapshot *pSnap = pDb->pWorker;
  ShmHeader *pShm = pDb->pShmhdr;
  void *p = 0;
  int n = 0;
  int rc;

  pSnap->iId++;
  rc = ckptExportSnapshot(pDb, bFlush, pSnap->iId, 1, &p, &n);
  if( rc!=LSM_OK ) return rc;
  assert( ckptChecksumOk((u32 *)p) );

  assert( n<=LSM_META_PAGE_SIZE );
  memcpy(pShm->aSnap2, p, n);
  lsmShmBarrier(pDb);
  memcpy(pShm->aSnap1, p, n);

Changes to src/lsm_file.c.

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    i64 nMin = (i64)nBlock * (i64)pFS->nBlocksize;
    fsGrowMapping(pFS, nMin, &rc);
    if( rc!=LSM_OK ) return rc;
  }
  return lsmEnvSync(pFS->pEnv, pFS->fdDb);
}

static int fsPageGet(FileSystem *, Pgno, int, Page **, int *);







































/*
** Parameter iBlock is a database file block. This function reads the value 
** stored in the blocks "next block" pointer and stores it in *piNext.
** LSM_OK is returned if everything is successful, or an LSM error code
** otherwise.
*/
static int fsBlockNext(
  FileSystem *pFS,                /* File-system object handle */

  int iBlock,                     /* Read field from this block */
  int *piNext                     /* OUT: Next block in linked list */
){
  int rc;








  assert( pFS->bUseMmap==0 || pFS->pCompress==0 );
  if( pFS->pCompress ){
    i64 iOff;                     /* File offset to read data from */
    u8 aNext[4];                  /* 4-byte pointer read from db file */

    iOff = (i64)iBlock * pFS->nBlocksize - sizeof(aNext);
    rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, aNext, sizeof(aNext));
    if( rc==LSM_OK ){
      *piNext = (int)lsmGetU32(aNext);
    }
  }else{
    const int nPagePerBlock = (pFS->nBlocksize / pFS->nPagesize);
    Page *pLast;
    rc = fsPageGet(pFS, iBlock*nPagePerBlock, 0, &pLast, 0);
    if( rc==LSM_OK ){
      *piNext = lsmGetU32(&pLast->aData[pFS->nPagesize-4]);
      lsmFsPageRelease(pLast);
    }
  }




  return rc;
}

/*
** Return the page number of the last page on the same block as page iPg.
*/
Pgno fsLastPageOnPagesBlock(FileSystem *pFS, Pgno iPg){
................................................................................
}

/*
** This function is only called in compressed database mode.
*/
static int fsReadData(
  FileSystem *pFS,                /* File-system handle */

  i64 iOff,                       /* Read data from this offset */
  u8 *aData,                      /* Buffer to read data into */
  int nData                       /* Number of bytes to read */
){
  i64 iEob;                       /* End of block */
  int nRead;
  int rc;
................................................................................
  iEob = fsLastPageOnPagesBlock(pFS, iOff) + 1;
  nRead = LSM_MIN(iEob - iOff, nData);

  rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, aData, nRead);
  if( rc==LSM_OK && nRead!=nData ){
    int iBlk;

    rc = fsBlockNext(pFS, fsPageToBlock(pFS, iOff), &iBlk);
    if( rc==LSM_OK ){
      i64 iOff2 = fsFirstPageOnBlock(pFS, iBlk);
      rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff2, &aData[nRead], nData-nRead);
    }
  }

  return rc;
................................................................................
** Parameter iBlock is a database file block. This function reads the value 
** stored in the blocks "previous block" pointer and stores it in *piPrev.
** LSM_OK is returned if everything is successful, or an LSM error code
** otherwise.
*/
static int fsBlockPrev(
  FileSystem *pFS,                /* File-system object handle */

  int iBlock,                     /* Read field from this block */
  int *piPrev                     /* OUT: Previous block in linked list */
){
  int rc = LSM_OK;                /* Return code */

  assert( pFS->bUseMmap==0 || pFS->pCompress==0 );
  assert( iBlock>0 );

  if( pFS->pCompress ){
    i64 iOff = fsFirstPageOnBlock(pFS, iBlock) - 4;
    u8 aPrev[4];                  /* 4-byte pointer read from db file */
    rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, aPrev, sizeof(aPrev));
    if( rc==LSM_OK ){

      *piPrev = (int)lsmGetU32(aPrev);
    }
  }else{
    assert( 0 );
  }
  return rc;
}

................................................................................
  nByte  = (aBuf[0] & 0x7F) << 14;
  nByte += (aBuf[1] & 0x7F) << 7;
  nByte += (aBuf[2] & 0x7F);
  *pbFree = !(aBuf[1] & 0x80);
  return nByte;
}

static int fsSubtractOffset(FileSystem *pFS, i64 iOff, int iSub, i64 *piRes){






  i64 iStart;
  int iBlk = 0;
  int rc;

  assert( pFS->pCompress );

  iStart = fsFirstPageOnBlock(pFS, fsPageToBlock(pFS, iOff));
  if( (iOff-iSub)>=iStart ){
    *piRes = (iOff-iSub);
    return LSM_OK;
  }

  rc = fsBlockPrev(pFS, fsPageToBlock(pFS, iOff), &iBlk);
  *piRes = fsLastPageOnBlock(pFS, iBlk) - iSub + (iOff - iStart + 1);
  return rc;
}

static int fsAddOffset(FileSystem *pFS, i64 iOff, int iAdd, i64 *piRes){






  i64 iEob;
  int iBlk;
  int rc;

  assert( pFS->pCompress );

  iEob = fsLastPageOnPagesBlock(pFS, iOff);
  if( (iOff+iAdd)<=iEob ){
    *piRes = (iOff+iAdd);
    return LSM_OK;
  }

  rc = fsBlockNext(pFS, fsPageToBlock(pFS, iOff), &iBlk);
  *piRes = fsFirstPageOnBlock(pFS, iBlk) + iAdd - (iEob - iOff + 1);
  return rc;
}

static int fsAllocateBuffer(FileSystem *pFS, int bWrite){
  u8 **pp;                        /* Pointer to either aIBuffer or aOBuffer */

................................................................................
** uncompresses the compressed data for page pPg from the database and
** populates the pPg->aData[] buffer and pPg->nCompress field.
**
** LSM_OK is returned if successful, or an LSM error code otherwise.
*/
static int fsReadPagedata(
  FileSystem *pFS,                /* File-system handle */

  Page *pPg,                      /* Page to read and uncompress data for */
  int *pnSpace                    /* OUT: Total bytes of free space */
){
  lsm_compress *p = pFS->pCompress;
  i64 iOff = pPg->iPg;
  u8 aSz[3];
  int rc;

  assert( p && pPg->nCompress==0 );

  if( fsAllocateBuffer(pFS, 0) ) return LSM_NOMEM;

  rc = fsReadData(pFS, iOff, aSz, sizeof(aSz));

  if( rc==LSM_OK ){
    int bFree;
    if( aSz[0] & 0x80 ){
      pPg->nCompress = (int)getRecordSize(aSz, &bFree);
    }else{
      pPg->nCompress = (int)aSz[0] - sizeof(aSz)*2;
................................................................................
    if( bFree ){
      if( pnSpace ){
        *pnSpace = pPg->nCompress + sizeof(aSz)*2;
      }else{
        rc = LSM_CORRUPT_BKPT;
      }
    }else{
      rc = fsAddOffset(pFS, iOff, 3, &iOff);
      if( rc==LSM_OK ){
        if( pPg->nCompress>pFS->nBuffer ){
          rc = LSM_CORRUPT_BKPT;
        }else{
          rc = fsReadData(pFS, iOff, pFS->aIBuffer, pPg->nCompress);
        }
        if( rc==LSM_OK ){
          int n = pFS->nPagesize;
          rc = p->xUncompress(p->pCtx, 
              (char *)pPg->aData, &n, 
              (const char *)pFS->aIBuffer, pPg->nCompress
          );
................................................................................
}

/*
** Return a handle for a database page.
*/
static int fsPageGet(
  FileSystem *pFS,                /* File-system handle */

  Pgno iPg,                       /* Page id */
  int noContent,                  /* True to not load content from disk */
  Page **ppPg,                    /* OUT: New page handle */
  int *pnSpace                    /* OUT: Bytes of free space */
){
  Page *p;
  int iHash;
  int rc = LSM_OK;






  assert( iPg>=fsFirstPageOnBlock(pFS, 1) );

  *ppPg = 0;

  assert( pFS->bUseMmap==0 || pFS->pCompress==0 );
  if( pFS->bUseMmap ){
    Page *pTest;
    i64 iEnd = (i64)iPg * pFS->nPagesize;
    fsGrowMapping(pFS, iEnd, &rc);
    if( rc!=LSM_OK ) return rc;

    p = 0;
    for(pTest=pFS->pWaiting; pTest; pTest=pTest->pNextWaiting){
      if( pTest->iPg==iPg ){

        p = pTest;
        p->nRef++;
        *ppPg = p;
        return LSM_OK;
      }
    }
    if( pFS->pFree ){
................................................................................
      assert( p->nRef==0 );
    }else{
      p = lsmMallocZeroRc(pFS->pEnv, sizeof(Page), &rc);
      if( rc ) return rc;
      fsPageAddToLru(pFS, p);
      p->pFS = pFS;
    }
    p->aData = &((u8 *)pFS->pMap)[pFS->nPagesize * (i64)(iPg-1)];
    p->iPg = iPg;
  }else{

    /* Search the hash-table for the page */
    iHash = fsHashKey(pFS->nHash, iPg);
    for(p=pFS->apHash[iHash]; p; p=p->pHashNext){
      if( p->iPg==iPg) break;
    }

    if( p==0 ){
      rc = fsPageBuffer(pFS, 1, &p);
      if( rc==LSM_OK ){
        int nSpace = 0;
        p->iPg = iPg;
        p->nRef = 0;
        p->pFS = pFS;
        assert( p->flags==0 || p->flags==PAGE_FREE );

#ifdef LSM_DEBUG
        memset(p->aData, 0x56, pFS->nPagesize);
#endif
        assert( p->pLruNext==0 && p->pLruPrev==0 );
        if( noContent==0 ){
          if( pFS->pCompress ){
            rc = fsReadPagedata(pFS, p, &nSpace);
          }else{
            int nByte = pFS->nPagesize;
            i64 iOff = (i64)(iPg-1) * pFS->nPagesize;
            rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, p->aData, nByte);
          }
          pFS->nRead++;
        }

        /* If the xRead() call was successful (or not attempted), link the
         ** page into the page-cache hash-table. Otherwise, if it failed,
................................................................................

    assert( (rc==LSM_OK && (p || (pnSpace && *pnSpace)))
         || (rc!=LSM_OK && p==0) 
    );
  }

  if( rc==LSM_OK && p ){
    if( pFS->pCompress==0 && (fsIsLast(pFS, iPg) || fsIsFirst(pFS, iPg)) ){
      p->nData = pFS->nPagesize - 4;
      if( fsIsFirst(pFS, iPg) && p->nRef==0 ){
        p->aData += 4;
        p->flags |= PAGE_HASPREV;
      }
    }else{
      p->nData = pFS->nPagesize;
    }
    pFS->nOut += (p->nRef==0);
................................................................................
    iBlk = fsPageToBlock(pFS, pDel->iFirst);
    iLastBlk = fsPageToBlock(pFS, pDel->iLastPg);

    /* Mark all blocks currently used by this sorted run as free */
    while( iBlk && rc==LSM_OK ){
      int iNext = 0;
      if( iBlk!=iLastBlk ){
        rc = fsBlockNext(pFS, iBlk, &iNext);
      }else if( bZero==0 && pDel->iLastPg!=fsLastPageOnBlock(pFS, iLastBlk) ){
        break;
      }
      rc = fsFreeBlock(pFS, pSnapshot, pDel, iBlk);
      iBlk = iNext;
    }






    if( bZero ) memset(pDel, 0, sizeof(Segment));
  }
  return LSM_OK;
}

static Pgno firstOnBlock(FileSystem *pFS, int iBlk, Pgno *aPgno, int nPgno){
................................................................................
    if( fsPageToBlock(pFS, iPg)==iBlk && (iRet==0 || iPg<iRet) ){
      iRet = iPg;
    }
  }
  return iRet;
}























/*
** Argument aPgno is an array of nPgno page numbers. All pages belong to
** the segment pRun. This function gobbles from the start of the run to the
** first page that appears in aPgno[] (i.e. so that the aPgno[] entry is
** the new first page of the run).
*/
void lsmFsGobble(
................................................................................
){
  int rc = LSM_OK;
  FileSystem *pFS = pDb->pFS;
  Snapshot *pSnapshot = pDb->pWorker;
  int iBlk;

  assert( pRun->nSize>0 );



  iBlk = fsPageToBlock(pFS, pRun->iFirst);
  pRun->nSize += (pRun->iFirst - fsFirstPageOnBlock(pFS, iBlk));

  while( rc==LSM_OK ){
    int iNext = 0;
    Pgno iFirst = firstOnBlock(pFS, iBlk, aPgno, nPgno);
    if( iFirst ){
      pRun->iFirst = iFirst;
      break;
    }
    rc = fsBlockNext(pFS, iBlk, &iNext);
    if( rc==LSM_OK ) rc = fsFreeBlock(pFS, pSnapshot, pRun, iBlk);
    pRun->nSize -= (
        1 + fsLastPageOnBlock(pFS, iBlk) - fsFirstPageOnBlock(pFS, iBlk)
    );
    iBlk = iNext;
  }

  pRun->nSize -= (pRun->iFirst - fsFirstPageOnBlock(pFS, iBlk));
  assert( pRun->nSize>0 );
}















static int fsNextPageOffset(
  FileSystem *pFS,                /* File system object */
  Segment *pSeg,                  /* Segment to move within */
  Pgno iPg,                       /* Offset of current page */
  int nByte,                      /* Size of current page including headers */
  Pgno *piNext                    /* OUT: Offset of next page. Or zero (EOF) */
){
  Pgno iNext;
  int rc;

  assert( pFS->pCompress );

  rc = fsAddOffset(pFS, iPg, nByte-1, &iNext);
  if( pSeg && iNext==pSeg->iLastPg ){
    iNext = 0;
  }else if( rc==LSM_OK ){
    rc = fsAddOffset(pFS, iNext, 1, &iNext);
  }

  *piNext = iNext;
  return rc;
}

static int fsGetPageBefore(FileSystem *pFS, i64 iOff, Pgno *piPrev){





  u8 aSz[3];
  int rc;
  i64 iRead;

  rc = fsSubtractOffset(pFS, iOff, sizeof(aSz), &iRead);
  if( rc==LSM_OK ) rc = fsReadData(pFS, iRead, aSz, sizeof(aSz));

  if( rc==LSM_OK ){
    int bFree;
    int nSz;
    if( aSz[2] & 0x80 ){
      nSz = getRecordSize(aSz, &bFree) + sizeof(aSz)*2;
    }else{
      nSz = (int)(aSz[2] & 0x7F);
      bFree = 1;
    }
    rc = fsSubtractOffset(pFS, iOff, nSz, piPrev);
  }

  return rc;
}

/*
** The first argument to this function is a valid reference to a database
................................................................................
** caller using lsmFsPageRelease().
*/
int lsmFsDbPageNext(Segment *pRun, Page *pPg, int eDir, Page **ppNext){
  int rc = LSM_OK;
  FileSystem *pFS = pPg->pFS;
  Pgno iPg = pPg->iPg;


  if( pFS->pCompress ){
    int nSpace = pPg->nCompress + 2*3;

    do {
      if( eDir>0 ){
        rc = fsNextPageOffset(pFS, pRun, iPg, nSpace, &iPg);
      }else{
        if( iPg==pRun->iFirst ){
          iPg = 0;
        }else{
          rc = fsGetPageBefore(pFS, iPg, &iPg);
        }
      }

      nSpace = 0;
      if( iPg!=0 ){
        rc = fsPageGet(pFS, iPg, 0, ppNext, &nSpace);
        assert( (*ppNext==0)==(rc!=LSM_OK || nSpace>0) );
      }else{
        *ppNext = 0;
      }
    }while( nSpace>0 && rc==LSM_OK );

  }else{

    assert( eDir==1 || eDir==-1 );
    if( eDir<0 ){
      if( pRun && iPg==pRun->iFirst ){
        *ppNext = 0;
        return LSM_OK;
      }else if( fsIsFirst(pFS, iPg) ){
        assert( pPg->flags & PAGE_HASPREV );
        iPg = fsLastPageOnBlock(pFS, lsmGetU32(&pPg->aData[-4]));
      }else{
        iPg--;
      }
    }else{

      if( pRun && iPg==pRun->iLastPg ){
        *ppNext = 0;
        return LSM_OK;



      }else if( fsIsLast(pFS, iPg) ){

        iPg = fsFirstPageOnBlock(pFS, lsmGetU32(&pPg->aData[pFS->nPagesize-4]));


      }else{
        iPg++;
      }
    }
    rc = fsPageGet(pFS, iPg, 0, ppNext, 0);
  }

  return rc;
}

static Pgno findAppendPoint(FileSystem *pFS, Level *pLvl){
  int i;
................................................................................
  int rc = LSM_OK;
  Page *pPg = 0;
  *ppOut = 0;
  int iApp = 0;
  int iNext = 0;
  Segment *p = &pLvl->lhs;
  int iPrev = p->iLastPg;



  if( pFS->pCompress || bDefer ){
    /* In compressed database mode the page is not assigned a page number
    ** or location in the database file at this point. This will be done
    ** by the lsmFsPagePersist() call.  */
    rc = fsPageBuffer(pFS, 1, &pPg);
    if( rc==LSM_OK ){
................................................................................
      pFS->nOut++;
    }
  }else{
    if( iPrev==0 ){
      iApp = findAppendPoint(pFS, pLvl);
    }else if( fsIsLast(pFS, iPrev) ){
      int iNext;
      rc = fsBlockNext(pFS, fsPageToBlock(pFS, iPrev), &iNext);
      if( rc!=LSM_OK ) return rc;
      iApp = fsFirstPageOnBlock(pFS, iNext);
    }else{
      iApp = iPrev + 1;
    }

    /* If this is the first page allocated, or if the page allocated is the
    ** last in the block, also allocate the next block here.  */
    if( iApp==0 || fsIsLast(pFS, iApp) ){
      int iNew;                     /* New block number */

      rc = lsmBlockAllocate(pFS->pDb, &iNew);
      if( rc!=LSM_OK ) return rc;
      if( iApp==0 ){
        iApp = fsFirstPageOnBlock(pFS, iNew);
      }else{
        iNext = fsFirstPageOnBlock(pFS, iNew);
      }
    }

    /* Grab the new page. */
    pPg = 0;
    rc = fsPageGet(pFS, iApp, 1, &pPg, 0);
    assert( rc==LSM_OK || pPg==0 );

    /* If this is the first or last page of a block, fill in the pointer 
     ** value at the end of the new page. */
    if( rc==LSM_OK ){
      p->nSize++;
      p->iLastPg = iApp;
................................................................................

/*
** Mark the sorted run passed as the second argument as finished. 
*/
int lsmFsSortedFinish(FileSystem *pFS, Segment *p){
  int rc = LSM_OK;
  if( p && p->iLastPg ){


    /* Check if the last page of this run happens to be the last of a block.
    ** If it is, then an extra block has already been allocated for this run.
    ** Shift this extra block back to the free-block list. 
    **
    ** Otherwise, add the first free page in the last block used by the run
    ** to the lAppend list.
................................................................................
        if( aiAppend[i]==0 ){
          aiAppend[i] = p->iLastPg+1;
          break;
        }
      }
    }else if( pFS->pCompress==0 ){
      Page *pLast;
      rc = fsPageGet(pFS, p->iLastPg, 0, &pLast, 0);
      if( rc==LSM_OK ){
        int iBlk = (int)lsmGetU32(&pLast->aData[pFS->nPagesize-4]);
        lsmBlockRefree(pFS->pDb, iBlk);
        lsmFsPageRelease(pLast);
      }
    }else{
      int iBlk = 0;
      rc = fsBlockNext(pFS, fsPageToBlock(pFS, p->iLastPg), &iBlk);
      if( rc==LSM_OK ){
        lsmBlockRefree(pFS->pDb, iBlk);
      }
    }
  }
  return rc;
}

/*
** Obtain a reference to page number iPg.
*/
int lsmFsDbPageGet(FileSystem *pFS, Pgno iPg, Page **ppPg){
  assert( pFS );
  return fsPageGet(pFS, iPg, 0, ppPg, 0);
}

/*
** Obtain a reference to the last page in the segment passed as the 
** second argument.
*/
int lsmFsDbPageLast(FileSystem *pFS, Segment *pSeg, Page **ppPg){
................................................................................
  int rc;
  Pgno iPg = pSeg->iLastPg;
  if( pFS->pCompress ){
    int nSpace;
    iPg++;
    do {
      nSpace = 0;
      rc = fsGetPageBefore(pFS, iPg, &iPg);
      if( rc==LSM_OK ){
        rc = fsPageGet(pFS, iPg, 0, ppPg, &nSpace);
      }
    }while( rc==LSM_OK && nSpace>0 );

  }else{
    rc = fsPageGet(pFS, iPg, 0, ppPg, 0);
  }
  return rc;
}

/*
** Return a reference to meta-page iPg. If successful, LSM_OK is returned
** and *ppPg populated with the new page reference. The reference should
................................................................................

/*
** Return true if page is currently writable.
*/
int lsmFsPageWritable(Page *pPg){
  return (pPg->flags & PAGE_DIRTY) ? 1 : 0;
}












































































/*
** Append raw data to a segment. This function is only used in compressed
** database mode.
*/
static Pgno fsAppendData(
  FileSystem *pFS,                /* File-system handle */
................................................................................

    /* If this is the first data written into the segment, find an append-point
    ** or allocate a new block.  */
    if( iApp==1 ){
      pSeg->iFirst = iApp = findAppendPoint(pFS, 0);
      if( iApp==0 ){
        int iBlk;
        rc = lsmBlockAllocate(pFS->pDb, &iBlk);
        pSeg->iFirst = iApp = fsFirstPageOnBlock(pFS, iBlk);
      }
    }
    iRet = iApp;

    /* Write as much data as is possible at iApp (usually all of it). */
    iLastOnBlock = fsLastPageOnPagesBlock(pFS, iApp);
................................................................................
    assert( nRem<=0 || (iApp-1)==iLastOnBlock );
    if( rc==LSM_OK && (iApp-1)==iLastOnBlock ){
      u8 aPtr[4];                 /* Space to serialize a u32 */
      int iBlk;                   /* New block number */

      if( nWrite>0 ){
        /* Allocate a new block. */
        rc = lsmBlockAllocate(pFS->pDb, &iBlk);

        /* Set the "next" pointer on the old block */
        if( rc==LSM_OK ){
          assert( iApp==(fsPageToBlock(pFS, iApp)*pFS->nBlocksize)-4 );
          lsmPutU32(aPtr, iBlk);
          rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iApp, aPtr, sizeof(aPtr));
        }
................................................................................
          iWrite = fsFirstPageOnBlock(pFS, iBlk);
          rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iWrite-4, aPtr, sizeof(aPtr));
          if( nRem>0 ) iApp = iWrite;
        }
      }else{
        /* The next block is already allocated. */
        assert( nRem>0 );

        rc = fsBlockNext(pFS, fsPageToBlock(pFS, iApp), &iBlk);
        iRet = iApp = fsFirstPageOnBlock(pFS, iBlk);
      }

      /* Write the remaining data into the new block */
      if( rc==LSM_OK && nRem>0 ){
        rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iApp, &aData[nWrite], nRem);
        iApp += nRem;
................................................................................
  if( fsIsLast(pFS, iPrev) ){
    /* Grab the first page on the next block (which has already be
    ** allocated). In this case set *piPrev to tell the caller to set
    ** the "previous block" pointer in the first 4 bytes of the page.
    */
    int iNext;
    int iBlk = fsPageToBlock(pFS, iPrev);

    rc = fsBlockNext(pFS, iBlk, &iNext);
    if( rc!=LSM_OK ) return rc;
    *piNew = fsFirstPageOnBlock(pFS, iNext);
    *piPrev = iBlk;
  }else{
    *piNew = iPrev+1;
    if( fsIsLast(pFS, *piNew) ){
      /* Allocate the next block here. */
      int iBlk;
      rc = lsmBlockAllocate(pFS->pDb, &iBlk);
      if( rc!=LSM_OK ) return rc;
      *piNext = iBlk;
    }
  }

  pSeg->nSize++;
  pSeg->iLastPg = *piNew;
................................................................................
    iBlk = fsPageToBlock(pFS, pArray->iFirst);
    iLastBlk = fsPageToBlock(pFS, pArray->iLastPg);

    lsmStringInit(&str, pDb->pEnv);
    if( bBlock ){
      lsmStringAppendf(&str, "%d", iBlk);
      while( iBlk!=iLastBlk ){
        fsBlockNext(pFS, iBlk, &iBlk);
        lsmStringAppendf(&str, " %d", iBlk);
      }
    }else{
      lsmStringAppendf(&str, "%d", pArray->iFirst);
      while( iBlk!=iLastBlk ){
        lsmStringAppendf(&str, " %d", fsLastPageOnBlock(pFS, iBlk));
        fsBlockNext(pFS, iBlk, &iBlk);
        lsmStringAppendf(&str, " %d", fsFirstPageOnBlock(pFS, iBlk));
      }
      lsmStringAppendf(&str, " %d", pArray->iLastPg);
    }

    *pzOut = str.z;
  }
................................................................................

  if( bUnlock ){
    int rcwork = LSM_BUSY;
    lsmFinishWork(pDb, 0, &rcwork);
  }
  return rc;
}

























/*
** This function implements the lsm_info(LSM_INFO_ARRAY_PAGES) request.
** If successful, *pzOut is set to point to a nul-terminated string 
** containing the array structure and LSM_OK is returned. The caller should
** eventually free the string using lsmFree().
**
** If an error occurs, *pzOut is set to NULL and an LSM error code returned.
*/
int lsmInfoArrayPages(lsm_db *pDb, Pgno iFirst, char **pzOut){
  int rc = LSM_OK;
  Snapshot *pWorker;              /* Worker snapshot */
  Segment *pArray = 0;            /* Array to report on */
  int bUnlock = 0;

  *pzOut = 0;
  if( iFirst==0 ) return LSM_ERROR;

  /* Obtain the worker snapshot */
  pWorker = pDb->pWorker;
................................................................................
    rc = lsmBeginWork(pDb);
    if( rc!=LSM_OK ) return rc;
    pWorker = pDb->pWorker;
    bUnlock = 1;
  }

  /* Search for the array that starts on page iFirst */
  pArray = findSegment(pWorker, iFirst);

  if( pArray==0 ){
    /* Could not find the requested array. This is an error. */
    rc = LSM_ERROR;
  }else{
    Page *pPg = 0;
    FileSystem *pFS = pDb->pFS;
    LsmString str;

    lsmStringInit(&str, pDb->pEnv);
    rc = lsmFsDbPageGet(pFS, iFirst, &pPg);
    while( rc==LSM_OK && pPg ){
      Page *pNext = 0;
      lsmStringAppendf(&str, " %lld", lsmFsPageNumber(pPg));
      rc = lsmFsDbPageNext(pArray, pPg, 1, &pNext);
      lsmFsPageRelease(pPg);
      pPg = pNext;
    }

    if( rc!=LSM_OK ){
      lsmFree(pDb->pEnv, str.z);
    }else{
................................................................................
  int bExtra,                     /* If true, count the "next" block if any */
  int nUsed,
  u8 *aUsed
){
  if( pSeg ){
    if( pSeg && pSeg->nSize>0 ){
      int rc;
      Pgno iLast = pSeg->iLastPg;
      int iBlk;
      int iLastBlk;

      int bLastIsLastOnBlock;


      iBlk = fsPageToBlock(pFS, pSeg->iFirst);
      iLastBlk = fsPageToBlock(pFS, pSeg->iLastPg);

      bLastIsLastOnBlock = (fsLastPageOnBlock(pFS, iLastBlk)==iLast);
      assert( iBlk>0 );

      /* If the first page of this run is also the first page of its first
      ** block, set the flag to indicate that the first page of iBlk is 
      ** in use.  */
      if( fsFirstPageOnBlock(pFS, iBlk)==pSeg->iFirst ){
        assert( (aUsed[iBlk-1] & INTEGRITY_CHECK_FIRST_PG)==0 );
        aUsed[iBlk-1] |= INTEGRITY_CHECK_FIRST_PG;
      }

      do {
        /* iBlk is a part of this sorted run. */
        aUsed[iBlk-1] |= INTEGRITY_CHECK_USED;









        /* Unless the sorted run finishes before the last page on this block, 
        ** the last page of this block is also in use.  */
        if( iBlk!=iLastBlk || bLastIsLastOnBlock ){
          assert( (aUsed[iBlk-1] & INTEGRITY_CHECK_LAST_PG)==0 );
          aUsed[iBlk-1] |= INTEGRITY_CHECK_LAST_PG;
        }
................................................................................

        /* Special case. The sorted run being scanned is the output run of
        ** a level currently undergoing an incremental merge. The sorted
        ** run ends on the last page of iBlk, but the next block has already
        ** been allocated. So mark it as in use as well.  */
        if( iBlk==iLastBlk && bLastIsLastOnBlock && bExtra ){
          int iExtra = 0;
          rc = fsBlockNext(pFS, iBlk, &iExtra);
          assert( rc==LSM_OK );

          assert( aUsed[iExtra-1]==0 );
          aUsed[iExtra-1] |= INTEGRITY_CHECK_USED;
          aUsed[iExtra-1] |= INTEGRITY_CHECK_FIRST_PG;
          aUsed[iExtra-1] |= INTEGRITY_CHECK_LAST_PG;
        }
................................................................................

        /* Move on to the next block in the sorted run. Or set iBlk to zero
        ** in order to break out of the loop if this was the last block in
        ** the run.  */
        if( iBlk==iLastBlk ){
          iBlk = 0;
        }else{
          rc = fsBlockNext(pFS, iBlk, &iBlk);
          assert( rc==LSM_OK );
        }
      }while( iBlk );
    }
  }
}








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    i64 nMin = (i64)nBlock * (i64)pFS->nBlocksize;
    fsGrowMapping(pFS, nMin, &rc);
    if( rc!=LSM_OK ) return rc;
  }
  return lsmEnvSync(pFS->pEnv, pFS->fdDb);
}

static int fsPageGet(FileSystem *, Segment *, Pgno, int, Page **, int *);

static int fsRedirectBlock(Redirect *p, int iBlk){
  if( p ){
    int i;
    for(i=0; i<p->n; i++){
      if( iBlk==p->a[i].iFrom ) return p->a[i].iTo;
    }
  }
  assert( iBlk!=0 );
  return iBlk;
}

Pgno lsmFsRedirectPage(FileSystem *pFS, Redirect *pRedir, Pgno iPg){
  Pgno iReal = iPg;

  if( pRedir ){
    const int nPagePerBlock = (
        pFS->pCompress ? pFS->nBlocksize : (pFS->nBlocksize / pFS->nPagesize)
    );
    int iBlk = fsPageToBlock(pFS, iPg);
    int i;
    for(i=0; i<pRedir->n; i++){
      int iFrom = pRedir->a[i].iFrom;
      if( iFrom>iBlk ) break;
      if( iFrom==iBlk ){
        int iTo = pRedir->a[i].iTo;
        iReal = iPg - (Pgno)(iFrom - iTo) * nPagePerBlock;
        if( iTo==1 ){
          iReal += (fsFirstPageOnBlock(pFS, 1)-1);
        }
        break;
      }
    }
  }

  assert( iReal!=0 );
  return iReal;
}

/*
** Parameter iBlock is a database file block. This function reads the value 
** stored in the blocks "next block" pointer and stores it in *piNext.
** LSM_OK is returned if everything is successful, or an LSM error code
** otherwise.
*/
static int fsBlockNext(
  FileSystem *pFS,                /* File-system object handle */
  Segment *pSeg,                  /* Use this segment for block redirects */
  int iBlock,                     /* Read field from this block */
  int *piNext                     /* OUT: Next block in linked list */
){
  int rc;
  int iRead;                      /* Read block from here */
  
  if( pSeg ){
    iRead = fsRedirectBlock(pSeg->pRedirect, iBlock);
  }else{
    iRead = iBlock;
  }

  assert( pFS->bUseMmap==0 || pFS->pCompress==0 );
  if( pFS->pCompress ){
    i64 iOff;                     /* File offset to read data from */
    u8 aNext[4];                  /* 4-byte pointer read from db file */

    iOff = (i64)iRead * pFS->nBlocksize - sizeof(aNext);
    rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, aNext, sizeof(aNext));
    if( rc==LSM_OK ){
      *piNext = (int)lsmGetU32(aNext);
    }
  }else{
    const int nPagePerBlock = (pFS->nBlocksize / pFS->nPagesize);
    Page *pLast;
    rc = fsPageGet(pFS, 0, iRead*nPagePerBlock, 0, &pLast, 0);
    if( rc==LSM_OK ){
      *piNext = lsmGetU32(&pLast->aData[pFS->nPagesize-4]);
      lsmFsPageRelease(pLast);
    }
  }

  if( pSeg ){
    *piNext = fsRedirectBlock(pSeg->pRedirect, *piNext);
  }
  return rc;
}

/*
** Return the page number of the last page on the same block as page iPg.
*/
Pgno fsLastPageOnPagesBlock(FileSystem *pFS, Pgno iPg){
................................................................................
}

/*
** This function is only called in compressed database mode.
*/
static int fsReadData(
  FileSystem *pFS,                /* File-system handle */
  Segment *pSeg,                  /* Block redirection */
  i64 iOff,                       /* Read data from this offset */
  u8 *aData,                      /* Buffer to read data into */
  int nData                       /* Number of bytes to read */
){
  i64 iEob;                       /* End of block */
  int nRead;
  int rc;
................................................................................
  iEob = fsLastPageOnPagesBlock(pFS, iOff) + 1;
  nRead = LSM_MIN(iEob - iOff, nData);

  rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, aData, nRead);
  if( rc==LSM_OK && nRead!=nData ){
    int iBlk;

    rc = fsBlockNext(pFS, pSeg, fsPageToBlock(pFS, iOff), &iBlk);
    if( rc==LSM_OK ){
      i64 iOff2 = fsFirstPageOnBlock(pFS, iBlk);
      rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff2, &aData[nRead], nData-nRead);
    }
  }

  return rc;
................................................................................
** Parameter iBlock is a database file block. This function reads the value 
** stored in the blocks "previous block" pointer and stores it in *piPrev.
** LSM_OK is returned if everything is successful, or an LSM error code
** otherwise.
*/
static int fsBlockPrev(
  FileSystem *pFS,                /* File-system object handle */
  Segment *pSeg,                  /* Use this segment for block redirects */
  int iBlock,                     /* Read field from this block */
  int *piPrev                     /* OUT: Previous block in linked list */
){
  int rc = LSM_OK;                /* Return code */

  assert( pFS->bUseMmap==0 || pFS->pCompress==0 );
  assert( iBlock>0 );

  if( pFS->pCompress ){
    i64 iOff = fsFirstPageOnBlock(pFS, iBlock) - 4;
    u8 aPrev[4];                  /* 4-byte pointer read from db file */
    rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, aPrev, sizeof(aPrev));
    if( rc==LSM_OK ){
      Redirect *pRedir = (pSeg ? pSeg->pRedirect : 0);
      *piPrev = fsRedirectBlock(pRedir, (int)lsmGetU32(aPrev));
    }
  }else{
    assert( 0 );
  }
  return rc;
}

................................................................................
  nByte  = (aBuf[0] & 0x7F) << 14;
  nByte += (aBuf[1] & 0x7F) << 7;
  nByte += (aBuf[2] & 0x7F);
  *pbFree = !(aBuf[1] & 0x80);
  return nByte;
}

static int fsSubtractOffset(
  FileSystem *pFS, 
  Segment *pSeg,
  i64 iOff, 
  int iSub, 
  i64 *piRes
){
  i64 iStart;
  int iBlk = 0;
  int rc;

  assert( pFS->pCompress );

  iStart = fsFirstPageOnBlock(pFS, fsPageToBlock(pFS, iOff));
  if( (iOff-iSub)>=iStart ){
    *piRes = (iOff-iSub);
    return LSM_OK;
  }

  rc = fsBlockPrev(pFS, pSeg, fsPageToBlock(pFS, iOff), &iBlk);
  *piRes = fsLastPageOnBlock(pFS, iBlk) - iSub + (iOff - iStart + 1);
  return rc;
}

static int fsAddOffset(
  FileSystem *pFS, 
  Segment *pSeg,
  i64 iOff, 
  int iAdd, 
  i64 *piRes
){
  i64 iEob;
  int iBlk;
  int rc;

  assert( pFS->pCompress );

  iEob = fsLastPageOnPagesBlock(pFS, iOff);
  if( (iOff+iAdd)<=iEob ){
    *piRes = (iOff+iAdd);
    return LSM_OK;
  }

  rc = fsBlockNext(pFS, pSeg, fsPageToBlock(pFS, iOff), &iBlk);
  *piRes = fsFirstPageOnBlock(pFS, iBlk) + iAdd - (iEob - iOff + 1);
  return rc;
}

static int fsAllocateBuffer(FileSystem *pFS, int bWrite){
  u8 **pp;                        /* Pointer to either aIBuffer or aOBuffer */

................................................................................
** uncompresses the compressed data for page pPg from the database and
** populates the pPg->aData[] buffer and pPg->nCompress field.
**
** LSM_OK is returned if successful, or an LSM error code otherwise.
*/
static int fsReadPagedata(
  FileSystem *pFS,                /* File-system handle */
  Segment *pSeg,                  /* pPg is part of this segment */
  Page *pPg,                      /* Page to read and uncompress data for */
  int *pnSpace                    /* OUT: Total bytes of free space */
){
  lsm_compress *p = pFS->pCompress;
  i64 iOff = pPg->iPg;
  u8 aSz[3];
  int rc;

  assert( p && pPg->nCompress==0 );

  if( fsAllocateBuffer(pFS, 0) ) return LSM_NOMEM;

  rc = fsReadData(pFS, pSeg, iOff, aSz, sizeof(aSz));

  if( rc==LSM_OK ){
    int bFree;
    if( aSz[0] & 0x80 ){
      pPg->nCompress = (int)getRecordSize(aSz, &bFree);
    }else{
      pPg->nCompress = (int)aSz[0] - sizeof(aSz)*2;
................................................................................
    if( bFree ){
      if( pnSpace ){
        *pnSpace = pPg->nCompress + sizeof(aSz)*2;
      }else{
        rc = LSM_CORRUPT_BKPT;
      }
    }else{
      rc = fsAddOffset(pFS, pSeg, iOff, 3, &iOff);
      if( rc==LSM_OK ){
        if( pPg->nCompress>pFS->nBuffer ){
          rc = LSM_CORRUPT_BKPT;
        }else{
          rc = fsReadData(pFS, pSeg, iOff, pFS->aIBuffer, pPg->nCompress);
        }
        if( rc==LSM_OK ){
          int n = pFS->nPagesize;
          rc = p->xUncompress(p->pCtx, 
              (char *)pPg->aData, &n, 
              (const char *)pFS->aIBuffer, pPg->nCompress
          );
................................................................................
}

/*
** Return a handle for a database page.
*/
static int fsPageGet(
  FileSystem *pFS,                /* File-system handle */
  Segment *pSeg,                  /* Block redirection to use (or NULL) */
  Pgno iPg,                       /* Page id */
  int noContent,                  /* True to not load content from disk */
  Page **ppPg,                    /* OUT: New page handle */
  int *pnSpace                    /* OUT: Bytes of free space */
){
  Page *p;
  int iHash;
  int rc = LSM_OK;

  /* In most cases iReal is the same as iPg. Except, if pSeg->pRedirect is 
  ** not NULL, and the block containing iPg has been redirected, then iReal
  ** is the page number after redirection.  */
  Pgno iReal = lsmFsRedirectPage(pFS, (pSeg ? pSeg->pRedirect : 0), iPg);

  assert( iPg>=fsFirstPageOnBlock(pFS, 1) );
  assert( iReal>=fsFirstPageOnBlock(pFS, 1) );
  *ppPg = 0;

  assert( pFS->bUseMmap==0 || pFS->pCompress==0 );
  if( pFS->bUseMmap ){
    Page *pTest;
    i64 iEnd = (i64)iReal * pFS->nPagesize;
    fsGrowMapping(pFS, iEnd, &rc);
    if( rc!=LSM_OK ) return rc;

    p = 0;
    for(pTest=pFS->pWaiting; pTest; pTest=pTest->pNextWaiting){
      if( pTest->iPg==iReal ){
        assert( iReal==iPg );
        p = pTest;
        p->nRef++;
        *ppPg = p;
        return LSM_OK;
      }
    }
    if( pFS->pFree ){
................................................................................
      assert( p->nRef==0 );
    }else{
      p = lsmMallocZeroRc(pFS->pEnv, sizeof(Page), &rc);
      if( rc ) return rc;
      fsPageAddToLru(pFS, p);
      p->pFS = pFS;
    }
    p->aData = &((u8 *)pFS->pMap)[pFS->nPagesize * (iReal-1)];
    p->iPg = iReal;
  }else{

    /* Search the hash-table for the page */
    iHash = fsHashKey(pFS->nHash, iReal);
    for(p=pFS->apHash[iHash]; p; p=p->pHashNext){
      if( p->iPg==iReal) break;
    }

    if( p==0 ){
      rc = fsPageBuffer(pFS, 1, &p);
      if( rc==LSM_OK ){
        int nSpace = 0;
        p->iPg = iReal;
        p->nRef = 0;
        p->pFS = pFS;
        assert( p->flags==0 || p->flags==PAGE_FREE );

#ifdef LSM_DEBUG
        memset(p->aData, 0x56, pFS->nPagesize);
#endif
        assert( p->pLruNext==0 && p->pLruPrev==0 );
        if( noContent==0 ){
          if( pFS->pCompress ){
            rc = fsReadPagedata(pFS, pSeg, p, &nSpace);
          }else{
            int nByte = pFS->nPagesize;
            i64 iOff = (i64)(iReal-1) * pFS->nPagesize;
            rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, p->aData, nByte);
          }
          pFS->nRead++;
        }

        /* If the xRead() call was successful (or not attempted), link the
         ** page into the page-cache hash-table. Otherwise, if it failed,
................................................................................

    assert( (rc==LSM_OK && (p || (pnSpace && *pnSpace)))
         || (rc!=LSM_OK && p==0) 
    );
  }

  if( rc==LSM_OK && p ){
    if( pFS->pCompress==0 && (fsIsLast(pFS, iReal) || fsIsFirst(pFS, iReal)) ){
      p->nData = pFS->nPagesize - 4;
      if( fsIsFirst(pFS, iReal) && p->nRef==0 ){
        p->aData += 4;
        p->flags |= PAGE_HASPREV;
      }
    }else{
      p->nData = pFS->nPagesize;
    }
    pFS->nOut += (p->nRef==0);
................................................................................
    iBlk = fsPageToBlock(pFS, pDel->iFirst);
    iLastBlk = fsPageToBlock(pFS, pDel->iLastPg);

    /* Mark all blocks currently used by this sorted run as free */
    while( iBlk && rc==LSM_OK ){
      int iNext = 0;
      if( iBlk!=iLastBlk ){
        rc = fsBlockNext(pFS, pDel, iBlk, &iNext);
      }else if( bZero==0 && pDel->iLastPg!=fsLastPageOnBlock(pFS, iLastBlk) ){
        break;
      }
      rc = fsFreeBlock(pFS, pSnapshot, pDel, iBlk);
      iBlk = iNext;
    }

    if( pDel->pRedirect ){
      assert( pDel->pRedirect==&pSnapshot->redirect );
      pSnapshot->redirect.n = 0;
    }

    if( bZero ) memset(pDel, 0, sizeof(Segment));
  }
  return LSM_OK;
}

static Pgno firstOnBlock(FileSystem *pFS, int iBlk, Pgno *aPgno, int nPgno){
................................................................................
    if( fsPageToBlock(pFS, iPg)==iBlk && (iRet==0 || iPg<iRet) ){
      iRet = iPg;
    }
  }
  return iRet;
}

#ifndef NDEBUG
/*
** Return true if page iPg, which is a part of segment p, lies on
** a redirected block. 
*/
static int fsPageRedirects(FileSystem *pFS, Segment *p, Pgno iPg){
  return (iPg!=0 && iPg!=lsmFsRedirectPage(pFS, p->pRedirect, iPg));
}

/*
** Return true if the second argument is not NULL and any of the first
** last or root pages lie on a redirected block. 
*/
static int fsSegmentRedirects(FileSystem *pFS, Segment *p){
  return (p && (
      fsPageRedirects(pFS, p, p->iFirst)
   || fsPageRedirects(pFS, p, p->iRoot)
   || fsPageRedirects(pFS, p, p->iLastPg)
  ));
}
#endif

/*
** Argument aPgno is an array of nPgno page numbers. All pages belong to
** the segment pRun. This function gobbles from the start of the run to the
** first page that appears in aPgno[] (i.e. so that the aPgno[] entry is
** the new first page of the run).
*/
void lsmFsGobble(
................................................................................
){
  int rc = LSM_OK;
  FileSystem *pFS = pDb->pFS;
  Snapshot *pSnapshot = pDb->pWorker;
  int iBlk;

  assert( pRun->nSize>0 );
  assert( 0==fsSegmentRedirects(pFS, pRun) );
  assert( nPgno>0 && 0==fsPageRedirects(pFS, pRun, aPgno[0]) );

  iBlk = fsPageToBlock(pFS, pRun->iFirst);
  pRun->nSize += (pRun->iFirst - fsFirstPageOnBlock(pFS, iBlk));

  while( rc==LSM_OK ){
    int iNext = 0;
    Pgno iFirst = firstOnBlock(pFS, iBlk, aPgno, nPgno);
    if( iFirst ){
      pRun->iFirst = iFirst;
      break;
    }
    rc = fsBlockNext(pFS, pRun, iBlk, &iNext);
    if( rc==LSM_OK ) rc = fsFreeBlock(pFS, pSnapshot, pRun, iBlk);
    pRun->nSize -= (
        1 + fsLastPageOnBlock(pFS, iBlk) - fsFirstPageOnBlock(pFS, iBlk)
    );
    iBlk = iNext;
  }

  pRun->nSize -= (pRun->iFirst - fsFirstPageOnBlock(pFS, iBlk));
  assert( pRun->nSize>0 );
}

/*
** This function is only used in compressed database mode.
**
** Argument iPg is the page number (byte offset) of a page within segment
** pSeg. The page record, including all headers, is nByte bytes in size.
** Before returning, set *piNext to the page number of the next page in
** the segment, or to zero if iPg is the last.
**
** In other words, do:
**
**   *piNext = iPg + nByte;
**
** But take block overflow and redirection into account.
*/
static int fsNextPageOffset(
  FileSystem *pFS,                /* File system object */
  Segment *pSeg,                  /* Segment to move within */
  Pgno iPg,                       /* Offset of current page */
  int nByte,                      /* Size of current page including headers */
  Pgno *piNext                    /* OUT: Offset of next page. Or zero (EOF) */
){
  Pgno iNext;
  int rc;

  assert( pFS->pCompress );

  rc = fsAddOffset(pFS, pSeg, iPg, nByte-1, &iNext);
  if( pSeg && iNext==pSeg->iLastPg ){
    iNext = 0;
  }else if( rc==LSM_OK ){
    rc = fsAddOffset(pFS, pSeg, iNext, 1, &iNext);
  }

  *piNext = iNext;
  return rc;
}

static int fsGetPageBefore(
  FileSystem *pFS, 
  Segment *pSeg, 
  i64 iOff, 
  Pgno *piPrev
){
  u8 aSz[3];
  int rc;
  i64 iRead;

  rc = fsSubtractOffset(pFS, pSeg, iOff, sizeof(aSz), &iRead);
  if( rc==LSM_OK ) rc = fsReadData(pFS, pSeg, iRead, aSz, sizeof(aSz));

  if( rc==LSM_OK ){
    int bFree;
    int nSz;
    if( aSz[2] & 0x80 ){
      nSz = getRecordSize(aSz, &bFree) + sizeof(aSz)*2;
    }else{
      nSz = (int)(aSz[2] & 0x7F);
      bFree = 1;
    }
    rc = fsSubtractOffset(pFS, pSeg, iOff, nSz, piPrev);
  }

  return rc;
}

/*
** The first argument to this function is a valid reference to a database
................................................................................
** caller using lsmFsPageRelease().
*/
int lsmFsDbPageNext(Segment *pRun, Page *pPg, int eDir, Page **ppNext){
  int rc = LSM_OK;
  FileSystem *pFS = pPg->pFS;
  Pgno iPg = pPg->iPg;

  assert( 0==fsSegmentRedirects(pFS, pRun) );
  if( pFS->pCompress ){
    int nSpace = pPg->nCompress + 2*3;

    do {
      if( eDir>0 ){
        rc = fsNextPageOffset(pFS, pRun, iPg, nSpace, &iPg);
      }else{
        if( iPg==pRun->iFirst ){
          iPg = 0;
        }else{
          rc = fsGetPageBefore(pFS, pRun, iPg, &iPg);
        }
      }

      nSpace = 0;
      if( iPg!=0 ){
        rc = fsPageGet(pFS, pRun, iPg, 0, ppNext, &nSpace);
        assert( (*ppNext==0)==(rc!=LSM_OK || nSpace>0) );
      }else{
        *ppNext = 0;
      }
    }while( nSpace>0 && rc==LSM_OK );

  }else{
    Redirect *pRedir = pRun ? pRun->pRedirect : 0;
    assert( eDir==1 || eDir==-1 );
    if( eDir<0 ){
      if( pRun && iPg==pRun->iFirst ){
        *ppNext = 0;
        return LSM_OK;
      }else if( fsIsFirst(pFS, iPg) ){
        assert( pPg->flags & PAGE_HASPREV );
        iPg = fsLastPageOnBlock(pFS, lsmGetU32(&pPg->aData[-4]));
      }else{
        iPg--;
      }
    }else{
      if( pRun ){
        if( iPg==pRun->iLastPg ){
          *ppNext = 0;
          return LSM_OK;
        }
      }

      if( fsIsLast(pFS, iPg) ){
        int iBlk = fsRedirectBlock(
            pRedir, lsmGetU32(&pPg->aData[pFS->nPagesize-4])
        );
        iPg = fsFirstPageOnBlock(pFS, iBlk);
      }else{
        iPg++;
      }
    }
    rc = fsPageGet(pFS, pRun, iPg, 0, ppNext, 0);
  }

  return rc;
}

static Pgno findAppendPoint(FileSystem *pFS, Level *pLvl){
  int i;
................................................................................
  int rc = LSM_OK;
  Page *pPg = 0;
  *ppOut = 0;
  int iApp = 0;
  int iNext = 0;
  Segment *p = &pLvl->lhs;
  int iPrev = p->iLastPg;

  assert( p->pRedirect==0 );

  if( pFS->pCompress || bDefer ){
    /* In compressed database mode the page is not assigned a page number
    ** or location in the database file at this point. This will be done
    ** by the lsmFsPagePersist() call.  */
    rc = fsPageBuffer(pFS, 1, &pPg);
    if( rc==LSM_OK ){
................................................................................
      pFS->nOut++;
    }
  }else{
    if( iPrev==0 ){
      iApp = findAppendPoint(pFS, pLvl);
    }else if( fsIsLast(pFS, iPrev) ){
      int iNext;
      rc = fsBlockNext(pFS, 0, fsPageToBlock(pFS, iPrev), &iNext);
      if( rc!=LSM_OK ) return rc;
      iApp = fsFirstPageOnBlock(pFS, iNext);
    }else{
      iApp = iPrev + 1;
    }

    /* If this is the first page allocated, or if the page allocated is the
    ** last in the block, also allocate the next block here.  */
    if( iApp==0 || fsIsLast(pFS, iApp) ){
      int iNew;                     /* New block number */

      rc = lsmBlockAllocate(pFS->pDb, 0, &iNew);
      if( rc!=LSM_OK ) return rc;
      if( iApp==0 ){
        iApp = fsFirstPageOnBlock(pFS, iNew);
      }else{
        iNext = fsFirstPageOnBlock(pFS, iNew);
      }
    }

    /* Grab the new page. */
    pPg = 0;
    rc = fsPageGet(pFS, 0, iApp, 1, &pPg, 0);
    assert( rc==LSM_OK || pPg==0 );

    /* If this is the first or last page of a block, fill in the pointer 
     ** value at the end of the new page. */
    if( rc==LSM_OK ){
      p->nSize++;
      p->iLastPg = iApp;
................................................................................

/*
** Mark the sorted run passed as the second argument as finished. 
*/
int lsmFsSortedFinish(FileSystem *pFS, Segment *p){
  int rc = LSM_OK;
  if( p && p->iLastPg ){
    assert( p->pRedirect==0 );

    /* Check if the last page of this run happens to be the last of a block.
    ** If it is, then an extra block has already been allocated for this run.
    ** Shift this extra block back to the free-block list. 
    **
    ** Otherwise, add the first free page in the last block used by the run
    ** to the lAppend list.
................................................................................
        if( aiAppend[i]==0 ){
          aiAppend[i] = p->iLastPg+1;
          break;
        }
      }
    }else if( pFS->pCompress==0 ){
      Page *pLast;
      rc = fsPageGet(pFS, 0, p->iLastPg, 0, &pLast, 0);
      if( rc==LSM_OK ){
        int iBlk = (int)lsmGetU32(&pLast->aData[pFS->nPagesize-4]);
        lsmBlockRefree(pFS->pDb, iBlk);
        lsmFsPageRelease(pLast);
      }
    }else{
      int iBlk = 0;
      rc = fsBlockNext(pFS, p, fsPageToBlock(pFS, p->iLastPg), &iBlk);
      if( rc==LSM_OK ){
        lsmBlockRefree(pFS->pDb, iBlk);
      }
    }
  }
  return rc;
}

/*
** Obtain a reference to page number iPg.
*/
int lsmFsDbPageGet(FileSystem *pFS, Segment *pSeg, Pgno iPg, Page **ppPg){
  assert( pFS );
  return fsPageGet(pFS, pSeg, iPg, 0, ppPg, 0);
}

/*
** Obtain a reference to the last page in the segment passed as the 
** second argument.
*/
int lsmFsDbPageLast(FileSystem *pFS, Segment *pSeg, Page **ppPg){
................................................................................
  int rc;
  Pgno iPg = pSeg->iLastPg;
  if( pFS->pCompress ){
    int nSpace;
    iPg++;
    do {
      nSpace = 0;
      rc = fsGetPageBefore(pFS, pSeg, iPg, &iPg);
      if( rc==LSM_OK ){
        rc = fsPageGet(pFS, pSeg, iPg, 0, ppPg, &nSpace);
      }
    }while( rc==LSM_OK && nSpace>0 );

  }else{
    rc = fsPageGet(pFS, pSeg, iPg, 0, ppPg, 0);
  }
  return rc;
}

/*
** Return a reference to meta-page iPg. If successful, LSM_OK is returned
** and *ppPg populated with the new page reference. The reference should
................................................................................

/*
** Return true if page is currently writable.
*/
int lsmFsPageWritable(Page *pPg){
  return (pPg->flags & PAGE_DIRTY) ? 1 : 0;
}

static void fsMovePage(
  FileSystem *pFS, 
  Segment *pSeg, 
  int iTo, 
  int iFrom, 
  Pgno *piPg
){
  Pgno iPg = *piPg;
  if( iFrom==fsPageToBlock(pFS, iPg) ){
    const int nPagePerBlock = (
        pFS->pCompress ? pFS ->nBlocksize : (pFS->nBlocksize / pFS->nPagesize)
    );
    *piPg = iPg - (Pgno)(iFrom - iTo) * nPagePerBlock;
  }
}

/*
** Copy the contents of block iFrom to block iTo. 
**
** It is safe to assume that there are no outstanding references to pages 
** on block iTo. And that block iFrom is not currently being written. In
** other words, the data can be read and written directly.
*/
int lsmFsMoveBlock(FileSystem *pFS, Segment *pSeg, int iTo, int iFrom){
  Snapshot *p = pFS->pDb->pWorker;
  int rc = LSM_OK;

  i64 iFromOff = (i64)(iFrom-1) * pFS->nBlocksize;
  i64 iToOff = (i64)(iTo-1) * pFS->nBlocksize;
  
  assert( iTo!=1 );
  assert( iFrom>iTo );

  if( pFS->bUseMmap ){
    fsGrowMapping(pFS, (i64)iFrom * pFS->nBlocksize, &rc);
    if( rc==LSM_OK ){
      u8 *aMap = (u8 *)(pFS->pMap);
      memcpy(&aMap[iToOff], &aMap[iFromOff], pFS->nBlocksize);
    }
  }else{
    int nSz = pFS->nPagesize;
    u8 *aData = (u8 *)lsmMallocRc(pFS->pEnv, nSz, &rc);
    if( rc==LSM_OK ){
      const int nPagePerBlock = (pFS->nBlocksize / pFS->nPagesize);
      int i;
      for(i=0; rc==LSM_OK && i<nPagePerBlock; i++){
        i64 iOff = iFromOff + i*nSz;
        rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, aData, nSz);
        if( rc==LSM_OK ){
          iOff = iToOff + i*nSz;
          rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iOff, aData, nSz);
        }
      }
    }
  }

  /* Update append-point list if necessary */
  if( rc==LSM_OK ){
    int i;
    for(i=0; i<LSM_APPLIST_SZ; i++){
      if( fsPageToBlock(pFS, p->aiAppend[i])==iFrom ){
        const int nPagePerBlock = (pFS->nBlocksize / pFS->nPagesize);
        p->aiAppend[i] -= (i64)(iFrom-iTo) * nPagePerBlock;
      }
    }
  }

  /* Update the Segment structure itself */
  fsMovePage(pFS, pSeg, iTo, iFrom, &pSeg->iFirst);
  fsMovePage(pFS, pSeg, iTo, iFrom, &pSeg->iLastPg);
  fsMovePage(pFS, pSeg, iTo, iFrom, &pSeg->iRoot);

  return rc;
}

/*
** Append raw data to a segment. This function is only used in compressed
** database mode.
*/
static Pgno fsAppendData(
  FileSystem *pFS,                /* File-system handle */
................................................................................

    /* If this is the first data written into the segment, find an append-point
    ** or allocate a new block.  */
    if( iApp==1 ){
      pSeg->iFirst = iApp = findAppendPoint(pFS, 0);
      if( iApp==0 ){
        int iBlk;
        rc = lsmBlockAllocate(pFS->pDb, 0, &iBlk);
        pSeg->iFirst = iApp = fsFirstPageOnBlock(pFS, iBlk);
      }
    }
    iRet = iApp;

    /* Write as much data as is possible at iApp (usually all of it). */
    iLastOnBlock = fsLastPageOnPagesBlock(pFS, iApp);
................................................................................
    assert( nRem<=0 || (iApp-1)==iLastOnBlock );
    if( rc==LSM_OK && (iApp-1)==iLastOnBlock ){
      u8 aPtr[4];                 /* Space to serialize a u32 */
      int iBlk;                   /* New block number */

      if( nWrite>0 ){
        /* Allocate a new block. */
        rc = lsmBlockAllocate(pFS->pDb, 0, &iBlk);

        /* Set the "next" pointer on the old block */
        if( rc==LSM_OK ){
          assert( iApp==(fsPageToBlock(pFS, iApp)*pFS->nBlocksize)-4 );
          lsmPutU32(aPtr, iBlk);
          rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iApp, aPtr, sizeof(aPtr));
        }
................................................................................
          iWrite = fsFirstPageOnBlock(pFS, iBlk);
          rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iWrite-4, aPtr, sizeof(aPtr));
          if( nRem>0 ) iApp = iWrite;
        }
      }else{
        /* The next block is already allocated. */
        assert( nRem>0 );
        assert( pSeg->pRedirect==0 );
        rc = fsBlockNext(pFS, 0, fsPageToBlock(pFS, iApp), &iBlk);
        iRet = iApp = fsFirstPageOnBlock(pFS, iBlk);
      }

      /* Write the remaining data into the new block */
      if( rc==LSM_OK && nRem>0 ){
        rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iApp, &aData[nWrite], nRem);
        iApp += nRem;
................................................................................
  if( fsIsLast(pFS, iPrev) ){
    /* Grab the first page on the next block (which has already be
    ** allocated). In this case set *piPrev to tell the caller to set
    ** the "previous block" pointer in the first 4 bytes of the page.
    */
    int iNext;
    int iBlk = fsPageToBlock(pFS, iPrev);
    assert( pSeg->pRedirect==0 );
    rc = fsBlockNext(pFS, 0, iBlk, &iNext);
    if( rc!=LSM_OK ) return rc;
    *piNew = fsFirstPageOnBlock(pFS, iNext);
    *piPrev = iBlk;
  }else{
    *piNew = iPrev+1;
    if( fsIsLast(pFS, *piNew) ){
      /* Allocate the next block here. */
      int iBlk;
      rc = lsmBlockAllocate(pFS->pDb, 0, &iBlk);
      if( rc!=LSM_OK ) return rc;
      *piNext = iBlk;
    }
  }

  pSeg->nSize++;
  pSeg->iLastPg = *piNew;
................................................................................
    iBlk = fsPageToBlock(pFS, pArray->iFirst);
    iLastBlk = fsPageToBlock(pFS, pArray->iLastPg);

    lsmStringInit(&str, pDb->pEnv);
    if( bBlock ){
      lsmStringAppendf(&str, "%d", iBlk);
      while( iBlk!=iLastBlk ){
        fsBlockNext(pFS, pArray, iBlk, &iBlk);
        lsmStringAppendf(&str, " %d", iBlk);
      }
    }else{
      lsmStringAppendf(&str, "%d", pArray->iFirst);
      while( iBlk!=iLastBlk ){
        lsmStringAppendf(&str, " %d", fsLastPageOnBlock(pFS, iBlk));
        fsBlockNext(pFS, pArray, iBlk, &iBlk);
        lsmStringAppendf(&str, " %d", fsFirstPageOnBlock(pFS, iBlk));
      }
      lsmStringAppendf(&str, " %d", pArray->iLastPg);
    }

    *pzOut = str.z;
  }
................................................................................

  if( bUnlock ){
    int rcwork = LSM_BUSY;
    lsmFinishWork(pDb, 0, &rcwork);
  }
  return rc;
}

int lsmFsSegmentContainsPg(
  FileSystem *pFS, 
  Segment *pSeg, 
  Pgno iPg, 
  int *pbRes
){
  Redirect *pRedir = pSeg->pRedirect;
  int rc = LSM_OK;
  int iBlk;
  int iLastBlk;
  int iPgBlock;                   /* Block containing page iPg */

  iPgBlock = fsPageToBlock(pFS, pSeg->iFirst);
  iBlk = fsRedirectBlock(pRedir, fsPageToBlock(pFS, pSeg->iFirst));
  iLastBlk = fsRedirectBlock(pRedir, fsPageToBlock(pFS, pSeg->iLastPg));

  while( iBlk!=iLastBlk && iBlk!=iPgBlock && rc==LSM_OK ){
    rc = fsBlockNext(pFS, pSeg, iBlk, &iBlk);
  }

  *pbRes = (iBlk==iPgBlock);
  return rc;
}

/*
** This function implements the lsm_info(LSM_INFO_ARRAY_PAGES) request.
** If successful, *pzOut is set to point to a nul-terminated string 
** containing the array structure and LSM_OK is returned. The caller should
** eventually free the string using lsmFree().
**
** If an error occurs, *pzOut is set to NULL and an LSM error code returned.
*/
int lsmInfoArrayPages(lsm_db *pDb, Pgno iFirst, char **pzOut){
  int rc = LSM_OK;
  Snapshot *pWorker;              /* Worker snapshot */
  Segment *pSeg = 0;              /* Array to report on */
  int bUnlock = 0;

  *pzOut = 0;
  if( iFirst==0 ) return LSM_ERROR;

  /* Obtain the worker snapshot */
  pWorker = pDb->pWorker;
................................................................................
    rc = lsmBeginWork(pDb);
    if( rc!=LSM_OK ) return rc;
    pWorker = pDb->pWorker;
    bUnlock = 1;
  }

  /* Search for the array that starts on page iFirst */
  pSeg = findSegment(pWorker, iFirst);

  if( pSeg==0 ){
    /* Could not find the requested array. This is an error. */
    rc = LSM_ERROR;
  }else{
    Page *pPg = 0;
    FileSystem *pFS = pDb->pFS;
    LsmString str;

    lsmStringInit(&str, pDb->pEnv);
    rc = lsmFsDbPageGet(pFS, pSeg, iFirst, &pPg);
    while( rc==LSM_OK && pPg ){
      Page *pNext = 0;
      lsmStringAppendf(&str, " %lld", lsmFsPageNumber(pPg));
      rc = lsmFsDbPageNext(pSeg, pPg, 1, &pNext);
      lsmFsPageRelease(pPg);
      pPg = pNext;
    }

    if( rc!=LSM_OK ){
      lsmFree(pDb->pEnv, str.z);
    }else{
................................................................................
  int bExtra,                     /* If true, count the "next" block if any */
  int nUsed,
  u8 *aUsed
){
  if( pSeg ){
    if( pSeg && pSeg->nSize>0 ){
      int rc;
      int iBlk;                   /* Current block (during iteration) */

      int iLastBlk;               /* Last block of segment */
      int iFirstBlk;              /* First block of segment */
      int bLastIsLastOnBlock;     /* True iLast is the last on its block */

      assert( 0==fsSegmentRedirects(pFS, pSeg) );
      iBlk = iFirstBlk = fsPageToBlock(pFS, pSeg->iFirst);
      iLastBlk = fsPageToBlock(pFS, pSeg->iLastPg);

      bLastIsLastOnBlock = (fsLastPageOnBlock(pFS, iLastBlk)==pSeg->iLastPg);
      assert( iBlk>0 );









      do {
        /* iBlk is a part of this sorted run. */
        aUsed[iBlk-1] |= INTEGRITY_CHECK_USED;

        /* If the first page of this block is also part of the segment,
        ** set the flag to indicate that the first page of iBlk is in use.  
        */
        if( fsFirstPageOnBlock(pFS, iBlk)==pSeg->iFirst || iBlk!=iFirstBlk ){
          assert( (aUsed[iBlk-1] & INTEGRITY_CHECK_FIRST_PG)==0 );
          aUsed[iBlk-1] |= INTEGRITY_CHECK_FIRST_PG;
        }

        /* Unless the sorted run finishes before the last page on this block, 
        ** the last page of this block is also in use.  */
        if( iBlk!=iLastBlk || bLastIsLastOnBlock ){
          assert( (aUsed[iBlk-1] & INTEGRITY_CHECK_LAST_PG)==0 );
          aUsed[iBlk-1] |= INTEGRITY_CHECK_LAST_PG;
        }
................................................................................

        /* Special case. The sorted run being scanned is the output run of
        ** a level currently undergoing an incremental merge. The sorted
        ** run ends on the last page of iBlk, but the next block has already
        ** been allocated. So mark it as in use as well.  */
        if( iBlk==iLastBlk && bLastIsLastOnBlock && bExtra ){
          int iExtra = 0;
          rc = fsBlockNext(pFS, pSeg, iBlk, &iExtra);
          assert( rc==LSM_OK );

          assert( aUsed[iExtra-1]==0 );
          aUsed[iExtra-1] |= INTEGRITY_CHECK_USED;
          aUsed[iExtra-1] |= INTEGRITY_CHECK_FIRST_PG;
          aUsed[iExtra-1] |= INTEGRITY_CHECK_LAST_PG;
        }
................................................................................

        /* Move on to the next block in the sorted run. Or set iBlk to zero
        ** in order to break out of the loop if this was the last block in
        ** the run.  */
        if( iBlk==iLastBlk ){
          iBlk = 0;
        }else{
          rc = fsBlockNext(pFS, pSeg, iBlk, &iBlk);
          assert( rc==LSM_OK );
        }
      }while( iBlk );
    }
  }
}

Changes to src/lsm_main.c.

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  /* If there is at least one cursor or a write transaction open, the database
  ** handle must be holding a pointer to a client snapshot. And the reverse 
  ** - if there are no open cursors and no write transactions then there must 
  ** not be a client snapshot.  */
  assert( (pDb->pCsr!=0 || pDb->nTransOpen>0)==(pDb->iReader>=0) );



  assert( pDb->nTransOpen>=0 );
}
#else
# define assert_db_state(x) 
#endif

/*
................................................................................

  assert( *pbUnlock==0 );
  if( !pDb->pWorker ){
    rc = lsmBeginWork(pDb);
    if( rc!=LSM_OK ) return rc;
    *pbUnlock = 1;
  }
  *pp = pDb->pWorker;
  return rc;
}

static void infoFreeWorker(lsm_db *pDb, int bUnlock){
  if( bUnlock ){
    int rcdummy = LSM_BUSY;
    lsmFinishWork(pDb, 0, &rcdummy);
................................................................................
      break;
    }

    case LSM_INFO_PAGE_HEX_DUMP:
    case LSM_INFO_PAGE_ASCII_DUMP: {
      Pgno pgno = va_arg(ap, Pgno);
      char **pzVal = va_arg(ap, char **);



      rc = lsmInfoPageDump(pDb, pgno, (eParam==LSM_INFO_PAGE_HEX_DUMP), pzVal);



      break;
    }

    case LSM_INFO_LOG_STRUCTURE: {
      char **pzVal = va_arg(ap, char **);
      rc = lsmInfoLogStructure(pDb, pzVal);
      break;







>
>







 







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>
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  /* If there is at least one cursor or a write transaction open, the database
  ** handle must be holding a pointer to a client snapshot. And the reverse 
  ** - if there are no open cursors and no write transactions then there must 
  ** not be a client snapshot.  */
  assert( (pDb->pCsr!=0 || pDb->nTransOpen>0)==(pDb->iReader>=0) );

  assert( pDb->iReader<0 || pDb->pClient!=0 );

  assert( pDb->nTransOpen>=0 );
}
#else
# define assert_db_state(x) 
#endif

/*
................................................................................

  assert( *pbUnlock==0 );
  if( !pDb->pWorker ){
    rc = lsmBeginWork(pDb);
    if( rc!=LSM_OK ) return rc;
    *pbUnlock = 1;
  }
  if( pp ) *pp = pDb->pWorker;
  return rc;
}

static void infoFreeWorker(lsm_db *pDb, int bUnlock){
  if( bUnlock ){
    int rcdummy = LSM_BUSY;
    lsmFinishWork(pDb, 0, &rcdummy);
................................................................................
      break;
    }

    case LSM_INFO_PAGE_HEX_DUMP:
    case LSM_INFO_PAGE_ASCII_DUMP: {
      Pgno pgno = va_arg(ap, Pgno);
      char **pzVal = va_arg(ap, char **);
      int bUnlock = 0;
      rc = infoGetWorker(pDb, 0, &bUnlock);
      if( rc==LSM_OK ){
        int bHex = (eParam==LSM_INFO_PAGE_HEX_DUMP);
        rc = lsmInfoPageDump(pDb, pgno, bHex, pzVal);
      }
      infoFreeWorker(pDb, bUnlock);
      break;
    }

    case LSM_INFO_LOG_STRUCTURE: {
      char **pzVal = va_arg(ap, char **);
      rc = lsmInfoLogStructure(pDb, pzVal);
      break;

Changes to src/lsm_shared.c.

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  DbTruncateCtx *p = (DbTruncateCtx *)pCtx;
  if( iBlk!=p->nBlock || (p->iInUse>=0 && iSnapshot>=p->iInUse) ) return 1;
  p->nBlock--;
  return 0;
}

static int dbTruncate(lsm_db *pDb, i64 iInUse){
  int rc;

  int i;
  DbTruncateCtx ctx;

  assert( pDb->pWorker );
  ctx.nBlock = pDb->pWorker->nBlock;
  ctx.iInUse = iInUse;

................................................................................
      lsmLogMessage(pDb, 0, 
          "dbTruncate(): truncated db to %d blocks",ctx.nBlock
      );
    }
#endif
    pDb->pWorker->nBlock = ctx.nBlock;
  }

  return rc;
}


/*
** This function is called during database shutdown (when the number of
** connections drops from one to zero). It truncates the database file
................................................................................
}


typedef struct FindFreeblockCtx FindFreeblockCtx;
struct FindFreeblockCtx {
  i64 iInUse;
  int iRet;

};

static int findFreeblockCb(void *pCtx, int iBlk, i64 iSnapshot){
  FindFreeblockCtx *p = (FindFreeblockCtx *)pCtx;
  if( iSnapshot<p->iInUse ){
    p->iRet = iBlk;
    return 1;
  }
  return 0;
}

static int findFreeblock(lsm_db *pDb, i64 iInUse, int *piRet){
  int rc;                         /* Return code */
  FindFreeblockCtx ctx;           /* Context object */

#ifdef LSM_LOG_BLOCKS
  char *zList = 0;
  lsmInfoFreelist(pDb, &zList);
  lsmLogMessage(pDb, 0, 
      "findFreeblock(): iInUse=%lld freelist=%s", iInUse, zList);
  lsmFree(pDb->pEnv, zList);
#endif

  ctx.iInUse = iInUse;
  ctx.iRet = 0;

  rc = lsmWalkFreelist(pDb, 0, findFreeblockCb, (void *)&ctx);
  *piRet = ctx.iRet;

#ifdef LSM_LOG_BLOCKS
  lsmLogMessage(pDb, 0, "findFreeblock(): returning block %d", *piRet);
#endif
  return rc;
}

/*
** Allocate a new database file block to write data to, either by extending
** the database file or by recycling a free-list entry. The worker snapshot 
** must be held in order to call this function.
**
** If successful, *piBlk is set to the block number allocated and LSM_OK is
** returned. Otherwise, *piBlk is zeroed and an lsm error code returned.
*/
int lsmBlockAllocate(lsm_db *pDb, int *piBlk){
  Snapshot *p = pDb->pWorker;
  int iRet = 0;                   /* Block number of allocated block */
  int rc = LSM_OK;
  i64 iInUse = 0;                 /* Snapshot id still in use */
  i64 iSynced = 0;                /* Snapshot id synced to disk */

  assert( p );

#ifdef LSM_LOG_FREELIST
  {

    char *zFree = 0;

    rc = lsmInfoFreelist(pDb, &zFree);
    if( rc!=LSM_OK ) return rc;
    lsmLogMessage(pDb, 0, "lsmBlockAllocate(): freelist: %s", zFree);
    lsmFree(pDb->pEnv, zFree);
  }
#endif

  /* Set iInUse to the smallest snapshot id that is either:
  **
  **   * Currently in use by a database client,
................................................................................
  **   * May be used by a database client in the future, or
  **   * Is the most recently checkpointed snapshot (i.e. the one that will
  **     be used following recovery if a failure occurs at this point).
  */
  rc = lsmCheckpointSynced(pDb, &iSynced, 0, 0);
  if( rc==LSM_OK && iSynced==0 ) iSynced = p->iId;
  iInUse = iSynced;


  if( rc==LSM_OK && pDb->pClient ) iInUse = LSM_MIN(iInUse, pDb->pClient->iId);

  if( rc==LSM_OK ) rc = firstSnapshotInUse(pDb, &iInUse);

#ifdef LSM_LOG_FREELIST
  {
    lsmLogMessage(pDb, 0, "lsmBlockAllocate(): "
        "snapshot-in-use: %lld (iSynced=%lld) (client-id=%lld)", 
        iInUse, iSynced, (pDb->pClient ? pDb->pClient->iId : 0)
    );
  }
#endif

  /* Query the free block list for a suitable block */
  if( rc==LSM_OK ) rc = findFreeblock(pDb, iInUse, &iRet);





  /* If a block was found in the free block list, use it and remove it from 
  ** the list. Otherwise, if no suitable block was found, allocate one from
  ** the end of the file.  */
  if( rc==LSM_OK ){
    if( iRet>0 ){
#ifdef LSM_LOG_FREELIST
      lsmLogMessage(pDb, 0, 
          "reusing block %d (snapshot-in-use=%lld)", iRet, iInUse);
#endif
      rc = freelistAppend(pDb, iRet, -1);
      if( rc==LSM_OK ){
................................................................................
      iRet = ++(p->nBlock);
#ifdef LSM_LOG_FREELIST
      lsmLogMessage(pDb, 0, "extending file to %d blocks", iRet);
#endif
    }
  }

  assert( iRet>0 || rc!=LSM_OK );
  *piBlk = iRet;
  return rc;
}

/*
** Free a database block. The worker snapshot must be held in order to call 
** this function.
................................................................................
  return rc;
}

void lsmFreeSnapshot(lsm_env *pEnv, Snapshot *p){
  if( p ){
    lsmSortedFreeLevel(pEnv, p->pLevel);
    lsmFree(pEnv, p->freelist.aEntry);

    lsmFree(pEnv, p);
  }
}

/*
** Argument bFlush is true if the contents of the in-memory tree has just
** been flushed to disk. The significance of this is that once the snapshot







|
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  DbTruncateCtx *p = (DbTruncateCtx *)pCtx;
  if( iBlk!=p->nBlock || (p->iInUse>=0 && iSnapshot>=p->iInUse) ) return 1;
  p->nBlock--;
  return 0;
}

static int dbTruncate(lsm_db *pDb, i64 iInUse){
  int rc = LSM_OK;
#if 0
  int i;
  DbTruncateCtx ctx;

  assert( pDb->pWorker );
  ctx.nBlock = pDb->pWorker->nBlock;
  ctx.iInUse = iInUse;

................................................................................
      lsmLogMessage(pDb, 0, 
          "dbTruncate(): truncated db to %d blocks",ctx.nBlock
      );
    }
#endif
    pDb->pWorker->nBlock = ctx.nBlock;
  }
#endif
  return rc;
}


/*
** This function is called during database shutdown (when the number of
** connections drops from one to zero). It truncates the database file
................................................................................
}


typedef struct FindFreeblockCtx FindFreeblockCtx;
struct FindFreeblockCtx {
  i64 iInUse;
  int iRet;
  int bNotOne;
};

static int findFreeblockCb(void *pCtx, int iBlk, i64 iSnapshot){
  FindFreeblockCtx *p = (FindFreeblockCtx *)pCtx;
  if( iSnapshot<p->iInUse && (iBlk!=1 || p->bNotOne==0) ){
    p->iRet = iBlk;
    return 1;
  }
  return 0;
}

static int findFreeblock(lsm_db *pDb, i64 iInUse, int bNotOne, int *piRet){
  int rc;                         /* Return code */
  FindFreeblockCtx ctx;           /* Context object */









  ctx.iInUse = iInUse;
  ctx.iRet = 0;
  ctx.bNotOne = bNotOne;
  rc = lsmWalkFreelist(pDb, 0, findFreeblockCb, (void *)&ctx);
  *piRet = ctx.iRet;




  return rc;
}

/*
** Allocate a new database file block to write data to, either by extending
** the database file or by recycling a free-list entry. The worker snapshot 
** must be held in order to call this function.
**
** If successful, *piBlk is set to the block number allocated and LSM_OK is
** returned. Otherwise, *piBlk is zeroed and an lsm error code returned.
*/
int lsmBlockAllocate(lsm_db *pDb, int iBefore, int *piBlk){
  Snapshot *p = pDb->pWorker;
  int iRet = 0;                   /* Block number of allocated block */
  int rc = LSM_OK;
  i64 iInUse = 0;                 /* Snapshot id still in use */
  i64 iSynced = 0;                /* Snapshot id synced to disk */

  assert( p );

#ifdef LSM_LOG_FREELIST
  {
    static int nCall = 0;
    char *zFree = 0;
    nCall++;
    rc = lsmInfoFreelist(pDb, &zFree);
    if( rc!=LSM_OK ) return rc;
    lsmLogMessage(pDb, 0, "lsmBlockAllocate(): %d freelist: %s", nCall, zFree);
    lsmFree(pDb->pEnv, zFree);
  }
#endif

  /* Set iInUse to the smallest snapshot id that is either:
  **
  **   * Currently in use by a database client,
................................................................................
  **   * May be used by a database client in the future, or
  **   * Is the most recently checkpointed snapshot (i.e. the one that will
  **     be used following recovery if a failure occurs at this point).
  */
  rc = lsmCheckpointSynced(pDb, &iSynced, 0, 0);
  if( rc==LSM_OK && iSynced==0 ) iSynced = p->iId;
  iInUse = iSynced;
  if( rc==LSM_OK && pDb->iReader>=0 ){
    assert( pDb->pClient );
    iInUse = LSM_MIN(iInUse, pDb->pClient->iId);
  }
  if( rc==LSM_OK ) rc = firstSnapshotInUse(pDb, &iInUse);

#ifdef LSM_LOG_FREELIST
  {
    lsmLogMessage(pDb, 0, "lsmBlockAllocate(): "
        "snapshot-in-use: %lld (iSynced=%lld) (client-id=%lld)", 
        iInUse, iSynced, (pDb->iReader>=0 ? pDb->pClient->iId : 0)
    );
  }
#endif

  /* Query the free block list for a suitable block */
  if( rc==LSM_OK ) rc = findFreeblock(pDb, iInUse, (iBefore>0), &iRet);

  if( iBefore>0 && (iRet<=0 || iRet>=iBefore) ){
    iRet = 0;

  }else if( rc==LSM_OK ){
    /* If a block was found in the free block list, use it and remove it from 
    ** the list. Otherwise, if no suitable block was found, allocate one from
    ** the end of the file.  */

    if( iRet>0 ){
#ifdef LSM_LOG_FREELIST
      lsmLogMessage(pDb, 0, 
          "reusing block %d (snapshot-in-use=%lld)", iRet, iInUse);
#endif
      rc = freelistAppend(pDb, iRet, -1);
      if( rc==LSM_OK ){
................................................................................
      iRet = ++(p->nBlock);
#ifdef LSM_LOG_FREELIST
      lsmLogMessage(pDb, 0, "extending file to %d blocks", iRet);
#endif
    }
  }

  assert( iBefore>0 || iRet>0 || rc!=LSM_OK );
  *piBlk = iRet;
  return rc;
}

/*
** Free a database block. The worker snapshot must be held in order to call 
** this function.
................................................................................
  return rc;
}

void lsmFreeSnapshot(lsm_env *pEnv, Snapshot *p){
  if( p ){
    lsmSortedFreeLevel(pEnv, p->pLevel);
    lsmFree(pEnv, p->freelist.aEntry);
    lsmFree(pEnv, p->redirect.a);
    lsmFree(pEnv, p);
  }
}

/*
** Argument bFlush is true if the contents of the in-memory tree has just
** been flushed to disk. The significance of this is that once the snapshot

Changes to src/lsm_sorted.c.

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....
1069
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1103

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1885




1886
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4174
....
4250
4251
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4257


4258
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4264
....
4299
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4306
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....
4427
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....
4491
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4497

























































































































































4498
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4500
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....
4514
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4534
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4577
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4608
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....
4649
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4656
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4679
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4685
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....
4747
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4751
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4755
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4757
4758












4759
4760
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4785
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....
5018
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....
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....
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....
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5147


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....
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....
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....
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*/

#ifndef _LSM_INT_H
# include "lsmInt.h"
#endif
#include "sqlite4.h"            /* only for sqlite4_snprintf() */




/*
** Macros to help decode record types.
*/
#define rtTopic(eType)       ((eType) & LSM_SYSTEMKEY)
#define rtIsDelete(eType)    (((eType) & 0x0F)==LSM_POINT_DELETE)

#define rtIsSeparator(eType) (((eType) & LSM_SEPARATOR)!=0)
................................................................................
static void sortedBlobFree(Blob *pBlob){
  assert( pBlob->pEnv || pBlob->pData==0 );
  if( pBlob->pData ) lsmFree(pBlob->pEnv, pBlob->pData);
  memset(pBlob, 0, sizeof(Blob));
}

static int sortedReadData(

  Page *pPg,
  int iOff,
  int nByte,
  void **ppData,
  Blob *pBlob
){
  int rc = LSM_OK;
................................................................................
      assert( nRem>=0 );
      if( nRem==0 ) break;
      i -= iEnd;

      /* Grab the next page in the segment */

      do {
        rc = lsmFsDbPageNext(0, pPg, 1, &pNext);
        if( rc==LSM_OK && pNext==0 ){
          rc = LSM_CORRUPT_BKPT;
        }
        if( rc ) break;
        lsmFsPageRelease(pPg);
        pPg = pNext;
        aData = fsPageData(pPg, &nData);
................................................................................
  assert( iCell<pageGetNRec(aData, nData) && iCell>=0 );
  aCell = pageGetCell(aData, nData, iCell);
  lsmVarintGet64(&aCell[1], &iRet);
  return iRet;
}

static u8 *pageGetKey(

  Page *pPg,                      /* Page to read from */
  int iCell,                      /* Index of cell on page to read */
  int *piTopic,                   /* OUT: Topic associated with this key */
  int *pnKey,                     /* OUT: Size of key in bytes */
  Blob *pBlob                     /* If required, use this for dynamic memory */
){
  u8 *pKey;
................................................................................
  pKey += lsmVarintGet32(pKey, &nDummy);
  pKey += lsmVarintGet32(pKey, pnKey);
  if( rtIsWrite(eType) ){
    pKey += lsmVarintGet32(pKey, &nDummy);
  }
  *piTopic = rtTopic(eType);

  sortedReadData(pPg, pKey-aData, *pnKey, (void **)&pKey, pBlob);
  return pKey;
}

static int pageGetKeyCopy(
  lsm_env *pEnv,                  /* Environment handle */

  Page *pPg,                      /* Page to read from */
  int iCell,                      /* Index of cell on page to read */
  int *piTopic,                   /* OUT: Topic associated with this key */
  Blob *pBlob                     /* If required, use this for dynamic memory */
){
  int rc = LSM_OK;
  int nKey;
  u8 *aKey;

  aKey = pageGetKey(pPg, iCell, piTopic, &nKey, pBlob);
  assert( (void *)aKey!=pBlob->pData || nKey==pBlob->nData );
  if( (void *)aKey!=pBlob->pData ){
    rc = sortedBlobSet(pEnv, pBlob, aKey, nKey);
  }

  return rc;
}
................................................................................
  return iRef;
}

#define GETVARINT64(a, i) (((i)=((u8*)(a))[0])<=240?1:lsmVarintGet64((a), &(i)))
#define GETVARINT32(a, i) (((i)=((u8*)(a))[0])<=240?1:lsmVarintGet32((a), &(i)))

static int pageGetBtreeKey(

  Page *pPg,
  int iKey, 
  Pgno *piPtr, 
  int *piTopic, 
  void **ppKey,
  int *pnKey,
  Blob *pBlob
................................................................................
  aCell += GETVARINT64(aCell, *piPtr);

  if( eType==0 ){
    int rc;
    Pgno iRef;                  /* Page number of referenced page */
    Page *pRef;
    aCell += GETVARINT64(aCell, iRef);
    rc = lsmFsDbPageGet(lsmPageFS(pPg), iRef, &pRef);
    if( rc!=LSM_OK ) return rc;
    pageGetKeyCopy(lsmPageEnv(pPg), pRef, 0, &eType, pBlob);
    lsmFsPageRelease(pRef);
    *ppKey = pBlob->pData;
    *pnKey = pBlob->nData;
  }else{
    aCell += GETVARINT32(aCell, *pnKey);
    *ppKey = aCell;
  }
................................................................................
    int iCell = pCsr->aPg[iPg].iCell;
    while( iCell<0 && (--iPg)>=0 ){
      iCell = pCsr->aPg[iPg].iCell-1;
    }
    if( iPg<0 || iCell<0 ) return LSM_CORRUPT_BKPT;

    rc = pageGetBtreeKey(

        pCsr->aPg[iPg].pPage, iCell,
        &dummy, &pCsr->eType, &pCsr->pKey, &pCsr->nKey, &pCsr->blob
    );
    pCsr->eType |= LSM_SEPARATOR;
  }

  return rc;
................................................................................
    if( pCsr->iPg>=0 ){
      pCsr->aPg[pCsr->iPg].iCell++;

      iLoad = btreeCursorPtr(aData, nData, pPg->iCell);
      do {
        Page *pLoad;
        pCsr->iPg++;
        rc = lsmFsDbPageGet(pCsr->pFS, iLoad, &pLoad);
        pCsr->aPg[pCsr->iPg].pPage = pLoad;
        pCsr->aPg[pCsr->iPg].iCell = 0;
        if( rc==LSM_OK ){
          if( pCsr->iPg==(pCsr->nDepth-1) ) break;
          aData = fsPageData(pLoad, &nData);
          iLoad = btreeCursorPtr(aData, nData, 0);
        }
................................................................................
  int rc;

  Page *pPg = 0;
  FileSystem *pFS = pCsr->pFS;
  int iPg = pCsr->pSeg->iRoot;

  do {
    rc = lsmFsDbPageGet(pFS, iPg, &pPg);
    assert( (rc==LSM_OK)==(pPg!=0) );
    if( rc==LSM_OK ){
      u8 *aData;
      int nData;
      int flags;

      aData = fsPageData(pPg, &nData);
................................................................................
  int rc = LSM_OK;

  if( p->iPg ){
    lsm_env *pEnv = lsmFsEnv(pCsr->pFS);
    int iCell;                    /* Current cell number on leaf page */
    Pgno iLeaf;                   /* Page number of current leaf page */
    int nDepth;                   /* Depth of b-tree structure */


    /* Decode the MergeInput structure */
    iLeaf = p->iPg;
    nDepth = (p->iCell & 0x00FF);
    iCell = (p->iCell >> 8) - 1;

    /* Allocate the BtreeCursor.aPg[] array */
    assert( pCsr->aPg==0 );
    pCsr->aPg = (BtreePg *)lsmMallocZeroRc(pEnv, sizeof(BtreePg) * nDepth, &rc);

    /* Populate the last entry of the aPg[] array */
    if( rc==LSM_OK ){

      pCsr->iPg = nDepth-1;
      pCsr->nDepth = nDepth;
      pCsr->aPg[pCsr->iPg].iCell = iCell;
      rc = lsmFsDbPageGet(pCsr->pFS, iLeaf, &pCsr->aPg[nDepth-1].pPage);
    }

    /* Populate any other aPg[] array entries */
    if( rc==LSM_OK && nDepth>1 ){
      Blob blob = {0,0,0};
      void *pSeek;
      int nSeek;
      int iTopicSeek;
      int iPg = 0;
      int iLoad = pCsr->pSeg->iRoot;
      Page *pPg = pCsr->aPg[nDepth-1].pPage;
 
      if( pageObjGetNRec(pPg)==0 ){
        /* This can happen when pPg is the right-most leaf in the b-tree.
        ** In this case, set the iTopicSeek/pSeek/nSeek key to a value
        ** greater than any real key.  */
        assert( iCell==-1 );
        iTopicSeek = 1000;
        pSeek = 0;
        nSeek = 0;
      }else{
        Pgno dummy;
        rc = pageGetBtreeKey(pPg,
            0, &dummy, &iTopicSeek, &pSeek, &nSeek, &pCsr->blob
        );
      }

      do {
        Page *pPg;
        rc = lsmFsDbPageGet(pCsr->pFS, iLoad, &pPg);
        assert( rc==LSM_OK || pPg==0 );
        if( rc==LSM_OK ){
          u8 *aData;                  /* Buffer containing page data */
          int nData;                  /* Size of aData[] in bytes */
          int iMin;
          int iMax;
          int iCell;
................................................................................
          while( iMax>=iMin ){
            int iTry = (iMin+iMax)/2;
            void *pKey; int nKey;         /* Key for cell iTry */
            int iTopic;                   /* Topic for key pKeyT/nKeyT */
            Pgno iPtr;                    /* Pointer for cell iTry */
            int res;                      /* (pSeek - pKeyT) */


            rc = pageGetBtreeKey(pPg, iTry, &iPtr, &iTopic, &pKey, &nKey,&blob);

            if( rc!=LSM_OK ) break;

            res = sortedKeyCompare(
                xCmp, iTopicSeek, pSeek, nSeek, iTopic, pKey, nKey
            );
            assert( res!=0 );

................................................................................
              iMin = iTry+1;
            }
          }

          pCsr->aPg[iPg].pPage = pPg;
          pCsr->aPg[iPg].iCell = iCell;
          iPg++;
          assert( iPg!=nDepth-1 || iLoad==iLeaf );


        }
      }while( rc==LSM_OK && iPg<(nDepth-1) );
      sortedBlobFree(&blob);
    }

    /* Load the current key and pointer */
    if( rc==LSM_OK ){
................................................................................
      if( pBtreePg->iCell<0 ){
        Pgno dummy;
        int i;
        for(i=pCsr->iPg-1; i>=0; i--){
          if( pCsr->aPg[i].iCell>0 ) break;
        }
        assert( i>=0 );
        rc = pageGetBtreeKey(
            pCsr->aPg[i].pPage, pCsr->aPg[i].iCell-1,
            &dummy, &pCsr->eType, &pCsr->pKey, &pCsr->nKey, &pCsr->blob
        );
        pCsr->eType |= LSM_SEPARATOR;

      }else{
        rc = btreeCursorLoadKey(pCsr);
................................................................................
  FileSystem *pFS,
  SegmentPtr *pPtr,              /* Load page into this SegmentPtr object */
  int iNew                       /* Page number of new page */
){
  Page *pPg = 0;                 /* The new page */
  int rc;                        /* Return Code */

  rc = lsmFsDbPageGet(pFS, iNew, &pPg);
  assert( rc==LSM_OK || pPg==0 );
  segmentPtrSetPage(pPtr, pPg);

  return rc;
}

static int segmentPtrReadData(
  SegmentPtr *pPtr,
  int iOff,
  int nByte,
  void **ppData,
  Blob *pBlob
){
  return sortedReadData(pPtr->pPg, iOff, nByte, ppData, pBlob);
}

static int segmentPtrNextPage(
  SegmentPtr *pPtr,              /* Load page into this SegmentPtr object */
  int eDir                       /* +1 for next(), -1 for prev() */
){
  Page *pNext;                   /* New page to load */
................................................................................
      pPtr->pVal = 0;
    }
  }

  return rc;
}




















void lsmSortedSplitkey(lsm_db *pDb, Level *pLevel, int *pRc){

  Page *pPg = 0;
  lsm_env *pEnv = pDb->pEnv;      /* Environment handle */
  int rc = *pRc;
  Merge *pMerge = pLevel->pMerge;


  if( rc==LSM_OK ){
    rc = lsmFsDbPageGet(pDb->pFS, pMerge->splitkey.iPg, &pPg);
  }
  if( rc==LSM_OK ){
    int iTopic;
    Blob blob = {0, 0, 0, 0};
    u8 *aData;
    int nData;
  
    aData = lsmFsPageData(pPg, &nData);
    if( pageGetFlags(aData, nData) & SEGMENT_BTREE_FLAG ){
      void *pKey;
      int nKey;
      Pgno dummy;
      rc = pageGetBtreeKey(
          pPg, pMerge->splitkey.iCell, &dummy, &iTopic, &pKey, &nKey, &blob
      );
      if( rc==LSM_OK && blob.pData!=pKey ){
        rc = sortedBlobSet(pEnv, &blob, pKey, nKey);
      }
    }else{

      rc = pageGetKeyCopy(pEnv, pPg, pMerge->splitkey.iCell, &iTopic, &blob);

    }

    pLevel->iSplitTopic = iTopic;
    pLevel->pSplitKey = blob.pData;
    pLevel->nSplitKey = blob.nData;
    lsmFsPageRelease(pPg);
  }
................................................................................
    if( svFlags && pPtr->pPg ){
      int res = sortedKeyCompare(pCsr->pDb->xCmp,
          rtTopic(pPtr->eType), pPtr->pKey, pPtr->nKey,
          pLvl->iSplitTopic, pLvl->pSplitKey, pLvl->nSplitKey
      );
      if( res<0 ) segmentPtrReset(pPtr);
    }

    if( pPtr->pPg==0 && (svFlags & LSM_END_DELETE) ){

      rc = lsmFsDbPageGet(pCsr->pDb->pFS, pPtr->pSeg->iFirst, &pPtr->pPg);
      if( rc!=LSM_OK ) return rc;

      pPtr->eType = LSM_START_DELETE | (pLvl->iSplitTopic ? LSM_SYSTEMKEY : 0);
      pPtr->pKey = pLvl->pSplitKey;
      pPtr->nKey = pLvl->nSplitKey;
    }

  }while( pCsr 
       && pPtr->pPg 
       && segmentPtrIgnoreSeparators(pCsr, pPtr)
................................................................................
static void segmentPtrEndPage(
  FileSystem *pFS, 
  SegmentPtr *pPtr, 
  int bLast, 
  int *pRc
){
  if( *pRc==LSM_OK ){

    Page *pNew = 0;
    if( bLast ){
      *pRc = lsmFsDbPageLast(pFS, pPtr->pSeg, &pNew);
    }else{
      *pRc = lsmFsDbPageGet(pFS, pPtr->pSeg->iFirst, &pNew);
    }
    segmentPtrSetPage(pPtr, pNew);
  }
}


/*
................................................................................
      && (pPtr->nCell==0 || (pPtr->flags & SEGMENT_BTREE_FLAG))
  ){
    rc = segmentPtrNextPage(pPtr, (bLast ? -1 : 1));
  }

  if( rc==LSM_OK && pPtr->pPg ){
    rc = segmentPtrLoadCell(pPtr, bLast ? (pPtr->nCell-1) : 0);







  }
  
  bIgnore = segmentPtrIgnoreSeparators(pCsr, pPtr);
  if( rc==LSM_OK && pPtr->pPg && bIgnore && rtIsSeparator(pPtr->eType) ){
    rc = segmentPtrAdvance(pCsr, pPtr, bLast);
  }


  if( bLast && rc==LSM_OK && pPtr->pPg
   && pPtr->pSeg==&pLvl->lhs 
   && pLvl->nRight && (pPtr->eType & LSM_START_DELETE)
  ){
    pPtr->iCell++;
    pPtr->eType = LSM_END_DELETE | (pLvl->iSplitTopic);
    pPtr->pKey = pLvl->pSplitKey;
    pPtr->nKey = pLvl->nSplitKey;
    pPtr->pVal = 0;
    pPtr->nVal = 0;
  }


  return rc;
}

static void segmentPtrKey(SegmentPtr *pPtr, void **ppKey, int *pnKey){
  assert( pPtr->pPg );
  *ppKey = pPtr->pKey;
................................................................................
  int iTopic = 0;                 /* TODO: Fix me */

  for(eDir=-1; eDir<=1; eDir+=2){
    Page *pTest = pPtr->pPg;

    lsmFsPageRef(pTest);
    while( pTest ){

      Page *pNext;

      int rc = lsmFsDbPageNext(pPtr->pSeg, pTest, eDir, &pNext);
      lsmFsPageRelease(pTest);
      if( rc ) return 1;
      pTest = pNext;

      if( pTest ){
        int nData;
        u8 *aData = fsPageData(pTest, &nData);
................................................................................
          int nPgKey;
          int iPgTopic;
          u8 *pPgKey;
          int res;
          int iCell;

          iCell = ((eDir < 0) ? (nCell-1) : 0);
          pPgKey = pageGetKey(pTest, iCell, &iPgTopic, &nPgKey, &blob);
          res = iTopic - iPgTopic;
          if( res==0 ) res = pCsr->pDb->xCmp(pKey, nKey, pPgKey, nPgKey);
          if( (eDir==1 && res>0) || (eDir==-1 && res<0) ){
            /* Taking this branch means something has gone wrong. */
            char *zMsg = lsmMallocPrintf(pEnv, "Key \"%s\" is not on page %d", 
                keyToString(pEnv, pKey, nKey), lsmFsPageNumber(pPtr->pPg)
            );
................................................................................
    u8 *pLastKey;
    int nLastKey;
    int iLastTopic;
    int res;                      /* Result of comparison */
    Page *pNext;

    /* Load the last key on the current page. */
    pLastKey = pageGetKey(
        pPtr->pPg, pPtr->nCell-1, &iLastTopic, &nLastKey, &pPtr->blob1
    );

    /* If the loaded key is >= than (pKey/nKey), break out of the loop.
    ** If (pKey/nKey) is present in this array, it must be on the current 
    ** page.  */
    res = sortedKeyCompare(
................................................................................
  do {
    Pgno *piFirst = 0;
    if( aPg ){
      aPg[i++] = iPg;
      piFirst = &aPg[i];
    }

    rc = lsmFsDbPageGet(pCsr->pDb->pFS, iPg, &pPg);
    assert( rc==LSM_OK || pPg==0 );
    if( rc==LSM_OK ){
      u8 *aData;                  /* Buffer containing page data */
      int nData;                  /* Size of aData[] in bytes */
      int iMin;
      int iMax;
      int nRec;
................................................................................
      while( iMax>=iMin ){
        int iTry = (iMin+iMax)/2;
        void *pKeyT; int nKeyT;       /* Key for cell iTry */
        int iTopicT;                  /* Topic for key pKeyT/nKeyT */
        Pgno iPtr;                    /* Pointer associated with cell iTry */
        int res;                      /* (pKey - pKeyT) */


        rc = pageGetBtreeKey(pPg, iTry, &iPtr, &iTopicT, &pKeyT, &nKeyT, &blob);

        if( rc!=LSM_OK ) break;
        if( piFirst && pKeyT==blob.pData ){
          *piFirst = pageGetBtreeRef(pPg, iTry);
          piFirst = 0;
          i++;
        }

................................................................................
    );
    if( rc==LSM_OK && nRhs>0 && eSeek==LSM_SEEK_GE && aPtr[0].pPg==0 ){
      res = 0;
    }
  }
  
  if( res>=0 ){

    int iPtr = *piPgno;
    int i;
    for(i=1; rc==LSM_OK && i<=nRhs && bStop==0; i++){

      iOut = 0;
      rc = seekInSegment(
          pCsr, &aPtr[i], iTopic, pKey, nKey, iPtr, eSeek, &iOut, &bStop
      );
      iPtr = iOut;
    }













    if( rc==LSM_OK && eSeek==LSM_SEEK_LE ){
      rc = segmentPtrEnd(pCsr, &aPtr[0], 1);
    }
  }

  assert( eSeek==LSM_SEEK_EQ || bStop==0 );
  *piPgno = iOut;
  *pbStop = bStop;
................................................................................
  MultiCursor *pCsr, 
  int iPtr,
  int bReverse
){
  int rc;
  SegmentPtr *pPtr = &pCsr->aPtr[iPtr];
  Level *pLvl = pPtr->pLevel;
  int bComposite;


  rc = segmentPtrAdvance(pCsr, pPtr, bReverse);
  if( rc!=LSM_OK ) return rc;

  bComposite = (pLvl->nRight>0 && pCsr->nPtr>pLvl->nRight);






























  if( bComposite && pPtr->pSeg==&pLvl->lhs       /* lhs of composite level */
   && bReverse==0                                /* csr advanced forwards */
   && pPtr->pPg==0                               /* segment at EOF */
  ){
    int i;
    for(i=0; rc==LSM_OK && i<pLvl->nRight; i++){
      rc = sortedRhsFirst(pCsr, pLvl, &pCsr->aPtr[iPtr+1+i]);
    }
    for(i=pCsr->nTree-1; i>0; i--){
      multiCursorDoCompare(pCsr, i, 0);
    }
  }


  return rc;
}

static void mcursorFreeComponents(MultiCursor *pCsr){
  int i;
  lsm_env *pEnv = pCsr->pDb->pEnv;
................................................................................
  for(i=0; i<nRhs; i++){
    pCsr->aPtr[i].pSeg = &pLvl->aRhs[i];
    pCsr->aPtr[i].pLevel = pLvl;
  }

  return LSM_OK;
}





















static int multiCursorAddAll(MultiCursor *pCsr, Snapshot *pSnap){
  Level *pLvl;
  int nPtr = 0;
  int iPtr = 0;
  int rc = LSM_OK;

................................................................................
    ** complete level may confuse it.  */
    if( pLvl->flags & LEVEL_INCOMPLETE ) continue;
    nPtr += (1 + pLvl->nRight);
  }

  assert( pCsr->aPtr==0 );
  pCsr->aPtr = lsmMallocZeroRc(pCsr->pDb->pEnv, sizeof(SegmentPtr) * nPtr, &rc);
  if( rc==LSM_OK ) pCsr->nPtr = nPtr;

  for(pLvl=pSnap->pLevel; pLvl && rc==LSM_OK; pLvl=pLvl->pNext){
    int i;
    if( pLvl->flags & LEVEL_INCOMPLETE ) continue;
    pCsr->aPtr[iPtr].pLevel = pLvl;
    pCsr->aPtr[iPtr].pSeg = &pLvl->lhs;
    iPtr++;
    for(i=0; i<pLvl->nRight; i++){
      pCsr->aPtr[iPtr].pLevel = pLvl;
      pCsr->aPtr[iPtr].pSeg = &pLvl->aRhs[i];
      iPtr++;
    }

    if( pLvl->nRight && pLvl->pSplitKey==0 ){
      lsmSortedSplitkey(pCsr->pDb, pLvl, &rc);

    }
  }

  return rc;
}

static int multiCursorInit(MultiCursor *pCsr, Snapshot *pSnap){
................................................................................
  void *pCtx                      /* First argument to pass to callback */
){
  MultiCursor *pCsr;              /* Cursor used to read db */
  int rc = LSM_OK;                /* Return Code */
  Snapshot *pSnap = 0;

  assert( pDb->pWorker );

  rc = lsmCheckpointDeserialize(pDb, 0, pDb->pShmhdr->aSnap1, &pSnap);
  if( rc!=LSM_OK ) return rc;




  pCsr = multiCursorNew(pDb, &rc);
  if( pCsr ){
    rc = multiCursorAddAll(pCsr, pSnap);
    pCsr->flags |= CURSOR_IGNORE_DELETE;
  }
  
................................................................................
        if( x(pCtx, iBlk, iSnap) ) break;
        rc = multiCursorAdvance(pCsr, !bReverse);
      }
    }
  }

  lsmMCursorClose(pCsr);

  lsmFreeSnapshot(pDb->pEnv, pSnap);


  return rc;
}

int lsmSortedLoadFreelist(
  lsm_db *pDb,                    /* Database handle (must be worker) */
  void **ppVal,                   /* OUT: Blob containing LSM free-list */
................................................................................
  if( *pRc==LSM_OK ){
    void *pKey;
    int nKey;
    multiCursorGetKey(pCsr, pCsr->aTree[1], &pCsr->eType, &pKey, &nKey);
    *pRc = sortedBlobSet(pCsr->pDb->pEnv, &pCsr->key, pKey, nKey);
  }
}































static int mcursorLocationOk(MultiCursor *pCsr, int bDeleteOk){
  int eType = pCsr->eType;
  int iKey;
  int i;
  int rdmask = 0;
  
  assert( pCsr->flags & (CURSOR_NEXT_OK|CURSOR_PREV_OK) );
  if( pCsr->flags & CURSOR_NEXT_OK ){
    rdmask = LSM_END_DELETE;
  }else{
    rdmask = LSM_START_DELETE;
  }





  if( (pCsr->flags & CURSOR_IGNORE_DELETE) && bDeleteOk==0 ){
    if( (eType & LSM_INSERT)==0 ) return 0;
  }



  if( (pCsr->flags & CURSOR_IGNORE_SYSTEM) && rtTopic(eType)!=0 ){
    return 0;
  }


























  /* Check if this key has already been deleted by a range-delete */



























  iKey = pCsr->aTree[1];
  for(i=0; i<iKey; i++){
    int csrflags;
    multiCursorGetKey(pCsr, i, &csrflags, 0, 0);
    if( (rdmask & csrflags) ){
      const int SD_ED = (LSM_START_DELETE|LSM_END_DELETE);
      if( (csrflags & SD_ED)==SD_ED 
................................................................................
          continue;
        }
      }
      return 0;
    }
  }

#if 0
  if( (iKey>0 && (rdmask & lsmTreeCursorFlags(pCsr->apTreeCsr[0]))) 
   || (iKey>1 && (rdmask & lsmTreeCursorFlags(pCsr->apTreeCsr[1]))) 
  ){
    return 0;
  }
  if( iKey>CURSOR_DATA_SYSTEM && (pCsr->flags & CURSOR_FLUSH_FREELIST) ){


    int eType;


    multiCursorGetKey(pCsr, CURSOR_DATA_SYSTEM, &eType, 0, 0);
    if( rdmask & eType ) return 0;


  }

  for(i=CURSOR_DATA_SEGMENT; i<iKey; i++){
    int iPtr = i-CURSOR_DATA_SEGMENT;
    if( pCsr->aPtr[iPtr].pPg && (pCsr->aPtr[iPtr].eType & rdmask) ){
      return 0;
    }


  }
#endif


  return 1;
}


static int multiCursorEnd(MultiCursor *pCsr, int bLast){
  int rc = LSM_OK;
  int i;

  pCsr->flags &= ~(CURSOR_NEXT_OK | CURSOR_PREV_OK);
  pCsr->flags |= (bLast ? CURSOR_PREV_OK : CURSOR_NEXT_OK);




  if( pCsr->apTreeCsr[0] ){
    rc = lsmTreeCursorEnd(pCsr->apTreeCsr[0], bLast);
  }
  if( rc==LSM_OK && pCsr->apTreeCsr[1] ){
    rc = lsmTreeCursorEnd(pCsr->apTreeCsr[1], bLast);
  }

  pCsr->iFree = 0;

  for(i=0; rc==LSM_OK && i<pCsr->nPtr; i++){
    SegmentPtr *pPtr = &pCsr->aPtr[i];
    Level *pLvl = pPtr->pLevel;









    rc = segmentPtrEnd(pCsr, pPtr, bLast);




    if( rc==LSM_OK && bLast==0 && pLvl->nRight && pPtr->pSeg==&pLvl->lhs ){
      int iRhs;
      for(iRhs=1+i; rc==LSM_OK && iRhs<1+i+pLvl->nRight; iRhs++){
        SegmentPtr *pRhs = &pCsr->aPtr[iRhs];




        if( pPtr->pPg==0 ){
          rc = sortedRhsFirst(pCsr, pLvl, pRhs);




        }else{
          segmentPtrReset(pRhs);

        }
      }

      i += pLvl->nRight;
    }
  }


  if( rc==LSM_OK && pCsr->pBtCsr ){
    assert( bLast==0 );
    rc = btreeCursorFirst(pCsr->pBtCsr);
  }

  if( rc==LSM_OK ){
    rc = multiCursorAllocTree(pCsr);
  }
  if( rc==LSM_OK ){
    for(i=pCsr->nTree-1; i>0; i--){
      multiCursorDoCompare(pCsr, i, bLast);
    }
  }

  multiCursorCacheKey(pCsr, &rc);
  if( rc==LSM_OK && mcursorLocationOk(pCsr, 0)==0 ){
    if( bLast ){
      rc = lsmMCursorPrev(pCsr);
    }else{
      rc = lsmMCursorNext(pCsr);
    }
  }

  return rc;
}


int mcursorSave(MultiCursor *pCsr){
  int rc = LSM_OK;
  if( pCsr->aTree ){
................................................................................

    /* If this cursor is configured to skip deleted keys, and the current
    ** cursor points to a SORTED_DELETE entry, then the cursor has not been 
    ** successfully advanced.  
    **
    ** Similarly, if the cursor is configured to skip system keys and the
    ** current cursor points to a system key, it has not yet been advanced.
     */
    if( *pRc==LSM_OK && 0==mcursorLocationOk(pCsr, 0) ) return 0;
  }
  return 1;
}

static void flCsrAdvance(MultiCursor *pCsr){
  assert( pCsr->flags & CURSOR_FLUSH_FREELIST );
................................................................................
}

static int multiCursorAdvance(MultiCursor *pCsr, int bReverse){
  int rc = LSM_OK;                /* Return Code */
  if( lsmMCursorValid(pCsr) ){
    do {
      int iKey = pCsr->aTree[1];



      /* If this multi-cursor is advancing forwards, and the sub-cursor
      ** being advanced is the one that separator keys may be being read
      ** from, record the current absolute pointer value.  */
      if( pCsr->pPrevMergePtr ){
        if( iKey==(CURSOR_DATA_SEGMENT+pCsr->nPtr) ){
          assert( pCsr->pBtCsr );
................................................................................
        rc = segmentCursorAdvance(pCsr, iKey-CURSOR_DATA_SEGMENT, bReverse);
      }
      if( rc==LSM_OK ){
        int i;
        for(i=(iKey+pCsr->nTree)/2; i>0; i=i/2){
          multiCursorDoCompare(pCsr, i, bReverse);
        }

      }
    }while( mcursorAdvanceOk(pCsr, bReverse, &rc)==0 );
  }
  return rc;
}

int lsmMCursorNext(MultiCursor *pCsr){
................................................................................

    do {
      Page *pPg = 0;
      u8 *aData;
      int nData;
      int flags;

      rc = lsmFsDbPageGet(pFS, iPg, &pPg);
      if( rc!=LSM_OK ) break;

      aData = fsPageData(pPg, &nData);
      flags = pageGetFlags(aData, nData);
      if( flags&SEGMENT_BTREE_FLAG ){
        Page **apNew = (Page **)lsmRealloc(
            pEnv, apHier, sizeof(Page *)*(nHier+1)
................................................................................

  if( pCsr->pBtCsr ){
    rc = LSM_OK;
    iFPtr = pMW->pLevel->pNext->lhs.iFirst;
  }else if( pCsr->nPtr>0 ){
    Segment *pSeg;
    pSeg = pCsr->aPtr[pCsr->nPtr-1].pSeg;
    rc = lsmFsDbPageGet(pMW->pDb->pFS, pSeg->iFirst, &pPg);
    if( rc==LSM_OK ){
      u8 *aData;                    /* Buffer for page pPg */
      int nData;                    /* Size of aData[] in bytes */
      aData = fsPageData(pPg, &nData);
      iFPtr = pageGetPtr(aData, nData);
      lsmFsPageRelease(pPg);
    }
................................................................................
    }
  }

  return rc;
}


static int multiCursorSetupTree(MultiCursor *pCsr, int bRev){
  int rc;

  assert( pCsr->aTree==0 );

  rc = multiCursorAllocTree(pCsr);
  if( rc==LSM_OK ){
    int i;
    for(i=pCsr->nTree-1; i>0; i--){
      multiCursorDoCompare(pCsr, i, bRev);
    }
  }

  multiCursorCacheKey(pCsr, &rc);
  return rc;
}

/*
** Free all resources allocated by mergeWorkerInit().
*/
static void mergeWorkerShutdown(MergeWorker *pMW, int *pRc){
  int i;                          /* Iterator variable */
  int rc = *pRc;
  MultiCursor *pCsr = pMW->pCsr;
................................................................................

  iVal = pCsr->aTree[1];
  mergeRangeDeletes(pCsr, &iVal, &eType);

  if( eType!=0 ){
    if( pMW->aGobble ){
      int iGobble = pCsr->aTree[1] - CURSOR_DATA_SEGMENT;
      if( iGobble<pCsr->nPtr ){
        SegmentPtr *pGobble = &pCsr->aPtr[iGobble];
        if( (pGobble->flags & PGFTR_SKIP_THIS_FLAG)==0 ){
          pMW->aGobble[iGobble] = lsmFsPageNumber(pGobble->pPg);
        }
      }
    }

................................................................................
    }
  }

  /* Advance the cursor to the next input record (assuming one exists). */
  assert( lsmMCursorValid(pMW->pCsr) );
  if( rc==LSM_OK ) rc = lsmMCursorNext(pMW->pCsr);

  /* If the cursor is at EOF, the merge is finished. Release all page
  ** references currently held by the merge worker and inform the 
  ** FileSystem object that no further pages will be appended to either 
  ** the main or separators array. 
  */
  if( rc==LSM_OK && !lsmMCursorValid(pMW->pCsr) ){

    mergeWorkerShutdown(pMW, &rc);
    if( pSeg->iFirst ){
      rc = lsmFsSortedFinish(pDb->pFS, pSeg);
    }

#ifdef LSM_DEBUG_EXPENSIVE
    if( rc==LSM_OK ){
#if 0
      rc = assertBtreeOk(pDb, pSeg);
      if( pMW->pCsr->pBtCsr ){
        Segment *pNext = &pMW->pLevel->pNext->lhs;
        rc = assertPointersOk(pDb, pSeg, pNext, 0);
      }
#endif
    }
#endif
  }
  return rc;
}

static int mergeWorkerDone(MergeWorker *pMW){
  return pMW->pCsr==0 || !lsmMCursorValid(pMW->pCsr);
}

................................................................................
  int eTree,                      /* One of the TREE_XXX constants */
  int *pnWrite                    /* OUT: Number of database pages written */
){
  int rc = LSM_OK;                /* Return Code */
  MultiCursor *pCsr = 0;
  Level *pNext = 0;               /* The current top level */
  Level *pNew;                    /* The new level itself */
  Segment *pDel = 0;              /* Delete separators from this segment */

  int nWrite = 0;                 /* Number of database pages written */
  Freelist freelist;

  if( eTree!=TREE_NONE ){
    rc = lsmShmCacheChunks(pDb, pDb->treehdr.nChunk);
  }

................................................................................
  pCsr = multiCursorNew(pDb, &rc);
  if( pCsr ){
    pCsr->pDb = pDb;
    rc = multiCursorVisitFreelist(pCsr);
    if( rc==LSM_OK ){
      rc = multiCursorAddTree(pCsr, pDb->pWorker, eTree);
    }
    if( rc==LSM_OK 
        && pNext && pNext->pMerge==0 && pNext->lhs.iRoot 
        && (eTree!=TREE_NONE || (pNext->flags & LEVEL_FREELIST_ONLY))

    ){


      pDel = &pNext->lhs;
      rc = btreeCursorNew(pDb, pDel, &pCsr->pBtCsr);

    }

    /* If this will be the only segment in the database, discard any delete
    ** markers present in the in-memory tree.  */
    if( pNext==0 ){
      multiCursorIgnoreDelete(pCsr);
    }
................................................................................
    mergeworker.bFlush = 1;

    /* Do the work to create the new merged segment on disk */
    if( rc==LSM_OK ) rc = lsmMCursorFirst(pCsr);
    while( rc==LSM_OK && mergeWorkerDone(&mergeworker)==0 ){
      rc = mergeWorkerStep(&mergeworker);
    }

    assert( rc!=LSM_OK || mergeworker.nWork==0 || pNew->lhs.iFirst );



    nWrite = mergeworker.nWork;
    mergeWorkerShutdown(&mergeworker, &rc);
    pNew->flags &= ~LEVEL_INCOMPLETE;
    if( eTree==TREE_NONE ){
      pNew->flags |= LEVEL_FREELIST_ONLY;
    }
    pNew->pMerge = 0;
  }

  if( rc!=LSM_OK || pNew->lhs.iFirst==0 ){
    assert( rc!=LSM_OK || pDb->pWorker->freelist.nEntry==0 );
    lsmDbSnapshotSetLevel(pDb->pWorker, pNext);
    sortedFreeLevel(pDb->pEnv, pNew);
  }else{

    if( pDel ) pDel->iRoot = 0;






#if 0


    lsmSortedDumpStructure(pDb, pDb->pWorker, 0, 0, "new-toplevel");
#endif

    if( freelist.nEntry ){
      Freelist *p = &pDb->pWorker->freelist;
      lsmFree(pDb->pEnv, p->aEntry);
      memcpy(p, &freelist, sizeof(freelist));
      freelist.aEntry = 0;
................................................................................
    pTopLevel = lsmDbSnapshotLevel(pDb->pWorker);
    pNew->pNext = p;
    for(pp=&pTopLevel; *pp!=pLevel; pp=&((*pp)->pNext));
    *pp = pNew;
    lsmDbSnapshotSetLevel(pDb->pWorker, pTopLevel);

    /* Determine whether or not the next separators will be linked in */
    if( pNext && pNext->pMerge==0 && pNext->lhs.iRoot ){


      bUseNext = 1;
    }
  }

  /* Allocate the merge object */
  nByte = sizeof(Merge) + sizeof(MergeInput) * (nMerge + bUseNext);
  pMerge = (Merge *)lsmMallocZeroRc(pDb->pEnv, nByte, &rc);
................................................................................
  **      separators attached to the LHS of the following level, or neither.
  **
  ** If the new level is the lowest (oldest) in the db, discard any
  ** delete keys. Key annihilation.
  */
  pCsr = multiCursorNew(pDb, &rc);
  if( pCsr ){

    rc = multiCursorAddRhs(pCsr, pLevel);
  }
  if( rc==LSM_OK && pMerge->nInput > pLevel->nRight ){
    rc = btreeCursorNew(pDb, &pNext->lhs, &pCsr->pBtCsr);
  }else if( pNext ){
    multiCursorReadSeparators(pCsr);
  }else{
................................................................................
  ** with the largest number of right-hand segments. Work on it. */
  for(pLevel=pTopLevel; pLevel; pLevel=pLevel->pNext){
    if( pLevel->nRight==0 && pThis && pLevel->iAge==pThis->iAge ){
      nThis++;
    }else{
      if( nThis>nBest ){
        if( (pLevel->iAge!=pThis->iAge+1)
            || (pLevel->nRight==0 && sortedCountLevels(pLevel)<=pDb->nMerge)
          ){
          pBest = pThis;
          nBest = nThis;
        }
      }
      if( pLevel->nRight ){
        if( pLevel->nRight>nBest ){
          nBest = pLevel->nRight;
................................................................................
  if( pTop && pTop->iAge==0
   && (pTop->nRight || sortedCountLevels(pTop)>=pDb->nMerge)
  ){
    return 1;
  }
  return 0;
}


























































































































































static int sortedWork(
  lsm_db *pDb,                    /* Database handle. Must be worker. */
  int nWork,                      /* Number of pages of work to do */
  int nMerge,                     /* Try to merge this many levels at once */
  int bFlush,                     /* Set if call is to make room for a flush */
  int *pnWrite                    /* OUT: Actual number of pages written */
................................................................................
    Level *pLevel = 0;

    /* Find a level to work on. */
    rc = sortedSelectLevel(pDb, nMerge, &pLevel);
    assert( rc==LSM_OK || pLevel==0 );

    if( pLevel==0 ){







      /* Could not find any work to do. Finished. */
      break;
    }else{


      MergeWorker mergeworker;    /* State used to work on the level merge */





      rc = mergeWorkerInit(pDb, pLevel, &mergeworker);
      assert( mergeworker.nWork==0 );

      while( rc==LSM_OK 
          && 0==mergeWorkerDone(&mergeworker) 
          && mergeworker.nWork<nRemaining 
      ){

        rc = mergeWorkerStep(&mergeworker);
      }




































      nRemaining -= LSM_MAX(mergeworker.nWork, 1);


      /* Check if the merge operation is completely finished. If so, the
      ** Merge object and the right-hand-side of the level can be deleted. 
      **
      ** Otherwise, gobble up (declare eligible for recycling) any pages
      ** from rhs segments for which the content has been completely merged
      ** into the lhs of the level.
      */
      if( rc==LSM_OK ){
        if( mergeWorkerDone(&mergeworker)==0 ){
          int i;
          for(i=0; i<pLevel->nRight; i++){
            SegmentPtr *pGobble = &mergeworker.pCsr->aPtr[i];
            if( pGobble->pSeg->iRoot ){
              rc = sortedBtreeGobble(pDb, mergeworker.pCsr, i);
            }else if( mergeworker.aGobble[i] ){
              lsmFsGobble(pDb, pGobble->pSeg, &mergeworker.aGobble[i], 1);
            }
          }
        }else if( pLevel->lhs.iFirst==0 ){
          /* If the new level is completely empty, remove it from the 
          ** database snapshot. This can only happen if all input keys were
          ** annihilated. Since keys are only annihilated if the new level
          ** is the last in the linked list (contains the most ancient of
          ** database content), this guarantees that pLevel->pNext==0.  */ 

          Level *pTop;          /* Top level of worker snapshot */
          Level **pp;           /* Read/write iterator for Level.pNext list */
          int i;
          assert( pLevel->pNext==0 );

          /* Remove the level from the worker snapshot. */
          pTop = lsmDbSnapshotLevel(pWorker);
          for(pp=&pTop; *pp!=pLevel; pp=&((*pp)->pNext));
          *pp = pLevel->pNext;
          lsmDbSnapshotSetLevel(pWorker, pTop);

          /* Free the Level structure. */
          lsmFsSortedDelete(pDb->pFS, pWorker, 1, &pLevel->lhs);
          for(i=0; i<pLevel->nRight; i++){
            lsmFsSortedDelete(pDb->pFS, pWorker, 1, &pLevel->aRhs[i]);
          }



















          sortedFreeLevel(pDb->pEnv, pLevel);
        }else{
          int i;

          /* Free the separators of the next level, if required. */
          if( pLevel->pMerge->nInput > pLevel->nRight ){
            assert( pLevel->pNext->lhs.iRoot );
            pLevel->pNext->lhs.iRoot = 0;
          }

          /* Free the right-hand-side of pLevel */
          for(i=0; i<pLevel->nRight; i++){
            lsmFsSortedDelete(pDb->pFS, pWorker, 1, &pLevel->aRhs[i]);
          }
          lsmFree(pDb->pEnv, pLevel->aRhs);
          pLevel->nRight = 0;
          pLevel->aRhs = 0;

          /* Free the Merge object */
          lsmFree(pDb->pEnv, pLevel->pMerge);
          pLevel->pMerge = 0;






        }
      }

      /* Clean up the MergeWorker object initialized above. If no error
      ** has occurred, invoke the work-hook to inform the application that
      ** the database structure has changed. */
      mergeWorkerShutdown(&mergeworker, &rc);

      if( rc==LSM_OK ) sortedInvokeWorkHook(pDb);

#if 0

      lsmSortedDumpStructure(pDb, pDb->pWorker, 0, 0, "work");
#endif
      assertBtreeOk(pDb, &pLevel->lhs);
      assertRunInOrder(pDb, &pLevel->lhs);

      /* If bFlush is true and the database is no longer considered "full",
      ** break out of the loop even if nRemaining is still greater than
      ** zero. The caller has an in-memory tree to flush to disk.  */
................................................................................
      bRet = 0;
    }
    *pRc = rc;
  }
  assert( *pRc==LSM_OK || bRet==0 );
  return bRet;
}









int lsmSaveWorker(lsm_db *pDb, int bFlush){
  Snapshot *p = pDb->pWorker;
  if( p->freelist.nEntry>pDb->nMaxFreelist ){
    int rc = sortedNewToplevel(pDb, TREE_NONE, 0);
    if( rc!=LSM_OK ) return rc;
  }
  return lsmCheckpointSaveWorker(pDb, bFlush);
}

static int doLsmSingleWork(
  lsm_db *pDb, 
  int bShutdown,
  int nMerge,                     /* Minimum segments to merge together */
  int nPage,                      /* Number of pages to write to disk */
  int *pnWrite,                   /* OUT: Pages actually written to disk */
  int *pbCkpt                     /* OUT: True if an auto-checkpoint is req. */
){

  int rc = LSM_OK;                /* Return code */
  int bDirty = 0;
  int nMax = nPage;               /* Maximum pages to write to disk */
  int nRem = nPage;
  int bCkpt = 0;



  /* Open the worker 'transaction'. It will be closed before this function
  ** returns.  */
  assert( pDb->pWorker==0 );
  rc = lsmBeginWork(pDb);
  if( rc!=LSM_OK ) return rc;


  /* If this connection is doing auto-checkpoints, set nMax (and nRem) so
  ** that this call stops writing when the auto-checkpoint is due. The
  ** caller will do the checkpoint, then possibly call this function again. */
  if( bShutdown==0 && pDb->nAutockpt ){
    u32 nSync;
    u32 nUnsync;
................................................................................
  if( rc==LSM_OK && pDb->pWorker->freelist.nEntry > pDb->nMaxFreelist ){
    int nPg = 0;
    while( rc==LSM_OK && lsmDatabaseFull(pDb) ){
      rc = sortedWork(pDb, 16, nMerge, 1, &nPg);
      nRem -= nPg;
    }
    if( rc==LSM_OK ){
      rc = sortedNewToplevel(pDb, TREE_NONE, &nPg);
    }
    nRem -= nPg;
    if( nPg ) bDirty = 1;
  }













  if( rc==LSM_OK && bDirty ){
    lsmFinishWork(pDb, 0, &rc);
  }else{
    int rcdummy = LSM_BUSY;
    lsmFinishWork(pDb, 0, &rcdummy);
  }
  assert( pDb->pWorker==0 );

  if( rc==LSM_OK ){
    *pnWrite = (nMax - nRem);
    *pbCkpt = (bCkpt && nRem<=0);
  }else{
    *pnWrite = 0;
    *pbCkpt = 0;
  }


  return rc;
}

static int doLsmWork(lsm_db *pDb, int nMerge, int nPage, int *pnWrite){
  int rc;
  int nWrite = 0;
  int bCkpt = 0;

  assert( nMerge>=1 );



  do {
    int nThis = 0;
    bCkpt = 0;
    rc = doLsmSingleWork(pDb, 0, nMerge, nPage-nWrite, &nThis, &bCkpt);
    nWrite += nThis;
    if( rc==LSM_OK && bCkpt ){
      rc = lsm_checkpoint(pDb, 0);
    }
  }while( rc==LSM_OK && (nWrite<nPage && bCkpt) );


  if( pnWrite ){
    if( rc==LSM_OK ){
      *pnWrite = nWrite;
    }else{
      *pnWrite = 0;
    }
................................................................................
    eType = *aCell++;
    assert( (flags & SEGMENT_BTREE_FLAG) || eType!=0 );
    aCell += lsmVarintGet32(aCell, &iPgPtr);

    if( eType==0 ){
      Pgno iRef;                  /* Page number of referenced page */
      aCell += lsmVarintGet64(aCell, &iRef);
      lsmFsDbPageGet(pDb->pFS, iRef, &pRef);
      aKey = pageGetKey(pRef, 0, &iTopic, &nKey, &blob);
    }else{
      aCell += lsmVarintGet32(aCell, &nKey);
      if( rtIsWrite(eType) ) aCell += lsmVarintGet32(aCell, &nVal);
      sortedReadData(pPg, (aCell-aData), nKey+nVal, (void **)&aKey, &blob);
      aVal = &aKey[nKey];
      iTopic = eType;
    }

    lsmStringAppendf(&s, "%s%2X:", (i==0?"":" "), iTopic);
    for(iChar=0; iChar<nKey; iChar++){
      lsmStringAppendf(&s, "%c", isalnum(aKey[iChar]) ? aKey[iChar] : '.');
................................................................................
  lsmLogMessage(pDb, LSM_OK, "      Page %d: %s", lsmFsPageNumber(pPg), s.z);
  lsmStringClear(&s);

  sortedBlobFree(&blob);
}

static void infoCellDump(
  lsm_db *pDb,

  int bIndirect,                  /* True to follow indirect refs */
  Page *pPg,
  int iCell,
  int *peType,
  int *piPgPtr,
  u8 **paKey, int *pnKey,
  u8 **paVal, int *pnVal,
................................................................................
  aCell += lsmVarintGet32(aCell, &iPgPtr);

  if( eType==0 ){
    int dummy;
    Pgno iRef;                  /* Page number of referenced page */
    aCell += lsmVarintGet64(aCell, &iRef);
    if( bIndirect ){
      lsmFsDbPageGet(pDb->pFS, iRef, &pRef);
      pageGetKeyCopy(pDb->pEnv, pRef, 0, &dummy, pBlob);
      aKey = (u8 *)pBlob->pData;
      nKey = pBlob->nData;
      lsmFsPageRelease(pRef);
    }else{
      aKey = (u8 *)"<indirect>";
      nKey = 11;
    }
  }else{
    aCell += lsmVarintGet32(aCell, &nKey);
    if( rtIsWrite(eType) ) aCell += lsmVarintGet32(aCell, &nVal);
    sortedReadData(pPg, (aCell-aData), nKey+nVal, (void **)&aKey, pBlob);
    aVal = &aKey[nKey];
  }

  if( peType ) *peType = eType;
  if( piPgPtr ) *piPgPtr = iPgPtr;
  if( paKey ) *paKey = aKey;
  if( paVal ) *paVal = aVal;
................................................................................
  int flags,
  char **pzOut                    /* OUT: lsmMalloc'd string */
){
  int rc = LSM_OK;                /* Return code */
  Page *pPg = 0;                  /* Handle for page iPg */
  int i, j;                       /* Loop counters */
  const int perLine = 16;         /* Bytes per line in the raw hex dump */



  int bValues = (flags & INFO_PAGE_DUMP_VALUES);
  int bHex = (flags & INFO_PAGE_DUMP_HEX);
  int bData = (flags & INFO_PAGE_DUMP_DATA);
  int bIndirect = (flags & INFO_PAGE_DUMP_INDIRECT);

  *pzOut = 0;
  if( iPg==0 ) return LSM_ERROR;



















  rc = lsmFsDbPageGet(pDb->pFS, iPg, &pPg);


  if( rc==LSM_OK ){
    Blob blob = {0, 0, 0, 0};
    int nKeyWidth = 0;
    LsmString str;
    int nRec;
    int iPtr;
    int flags;
................................................................................
    lsmStringAppendf(&str, "nRec : %d\n", nRec);
    lsmStringAppendf(&str, "iPtr : %d\n", iPtr);
    lsmStringAppendf(&str, "flags: %04x\n", flags);
    lsmStringAppendf(&str, "\n");

    for(iCell=0; iCell<nRec; iCell++){
      int nKey;

      infoCellDump(pDb, bIndirect, pPg, iCell, 0, 0, 0, &nKey, 0, 0, &blob);

      if( nKey>nKeyWidth ) nKeyWidth = nKey;
    }
    if( bHex ) nKeyWidth = nKeyWidth * 2;

    for(iCell=0; iCell<nRec; iCell++){
      u8 *aKey; int nKey = 0;       /* Key */
      u8 *aVal; int nVal = 0;       /* Value */
      int iPgPtr;
      int eType;
      char cType = '?';
      Pgno iAbsPtr;
      char zFlags[8];

      infoCellDump(pDb, bIndirect, pPg, iCell, &eType, &iPgPtr,
          &aKey, &nKey, &aVal, &nVal, &blob
      );
      iAbsPtr = iPgPtr + ((flags & SEGMENT_BTREE_FLAG) ? 0 : iPtr);

      lsmFlagsToString(eType, zFlags);
      lsmStringAppendf(&str, "%s %d (%s) ", 
          zFlags, iAbsPtr, (rtTopic(eType) ? "sys" : "usr")
................................................................................
    char *zSeg;
    Page *pPg;

    zSeg = segToString(pDb->pEnv, pRun, 0);
    lsmLogMessage(pDb, LSM_OK, "Segment: %s", zSeg);
    lsmFree(pDb->pEnv, zSeg);

    lsmFsDbPageGet(pDb->pFS, pRun->iFirst, &pPg);
    while( pPg ){
      Page *pNext;
      char *z = 0;
      infoPageDump(pDb, lsmFsPageNumber(pPg), flags, &z);
      lsmLogMessage(pDb, LSM_OK, "%s", z);
      lsmFree(pDb->pEnv, z);
#if 0
................................................................................
  Snapshot *pSnap,                /* Snapshot to dump */
  int bKeys,                      /* Output the keys from each segment */
  int bVals,                      /* Output the values from each segment */
  const char *zWhy                /* Caption to print near top of dump */
){
  Snapshot *pDump = pSnap;
  Level *pTopLevel;



  assert( pSnap );
  pTopLevel = lsmDbSnapshotLevel(pDump);
  if( pDb->xLog && pTopLevel ){

    Level *pLevel;
    int iLevel = 0;


    lsmLogMessage(pDb, LSM_OK, "Database structure (%s)", zWhy);





    for(pLevel=pTopLevel; pLevel; pLevel=pLevel->pNext){
      char zLeft[1024];
      char zRight[1024];
      int i = 0;

      Segment *aLeft[24];  
................................................................................
        sortedDumpSegment(pDb, &pLevel->lhs, bVals);
        for(i=0; i<pLevel->nRight; i++){
          sortedDumpSegment(pDb, &pLevel->aRhs[i], bVals);
        }
      }
    }
  }






}

void lsmSortedFreeLevel(lsm_env *pEnv, Level *pLevel){
  Level *pNext;
  Level *p;

  for(p=pLevel; p; p=pNext){
................................................................................

#ifdef LSM_DEBUG_EXPENSIVE
static void assertRunInOrder(lsm_db *pDb, Segment *pSeg){
  Page *pPg = 0;
  Blob blob1 = {0, 0, 0, 0};
  Blob blob2 = {0, 0, 0, 0};

  lsmFsDbPageGet(pDb->pFS, pSeg->iFirst, &pPg);
  while( pPg ){
    u8 *aData; int nData;
    Page *pNext;

    aData = lsmFsPageData(pPg, &nData);
    if( 0==(pageGetFlags(aData, nData) & SEGMENT_BTREE_FLAG) ){
      int i;
      int nRec = pageGetNRec(aData, nData);
      for(i=0; i<nRec; i++){
        int iTopic1, iTopic2;
        pageGetKeyCopy(pDb->pEnv, pPg, i, &iTopic1, &blob1);

        if( i==0 && blob2.nData ){
          assert( sortedKeyCompare(
                pDb->xCmp, iTopic2, blob2.pData, blob2.nData,
                iTopic1, blob1.pData, blob1.nData
          )<0 );
        }

        if( i<(nRec-1) ){
          pageGetKeyCopy(pDb->pEnv, pPg, i+1, &iTopic2, &blob2);
          assert( sortedKeyCompare(
                pDb->xCmp, iTopic1, blob1.pData, blob1.nData,
                iTopic2, blob2.pData, blob2.nData
          )<0 );
        }
      }
    }
................................................................................
    BtreeCursor *pCsr = 0;        /* Btree cursor */

    rc = btreeCursorNew(pDb, pSeg, &pCsr);
    if( rc==LSM_OK ){
      rc = btreeCursorFirst(pCsr);
    }
    if( rc==LSM_OK ){
      rc = lsmFsDbPageGet(pFS, pSeg->iFirst, &pPg);
    }

    while( rc==LSM_OK ){
      Page *pNext;
      u8 *aData;
      int nData;
      int flags;
................................................................................
      if( rc==LSM_OK 
       && 0==((SEGMENT_BTREE_FLAG|PGFTR_SKIP_THIS_FLAG) & flags)
       && 0!=pageGetNRec(aData, nData)
      ){
        u8 *pKey;
        int nKey;
        int iTopic;
        pKey = pageGetKey(pPg, 0, &iTopic, &nKey, &blob);
        assert( nKey==pCsr->nKey && 0==memcmp(pKey, pCsr->pKey, nKey) );
        assert( lsmFsPageNumber(pPg)==pCsr->iPtr );
        rc = btreeCursorNext(pCsr);
      }
    }
    assert( rc!=LSM_OK || pCsr->pKey==0 );








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....
1338
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....
1359
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1372
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....
1429
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....
1772
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....
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....
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....
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2209
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....
2311
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....
2350
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2357
2358

2359











2360
2361
2362
2363
2364
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2366
2367
....
2514
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....
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....
2628
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2674
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....
2758
2759
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2766
2767

2768
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2779
2780
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2803


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2823
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2828
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2833
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2840
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2849











2850
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2856
....
3084
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....
3122
3123
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3137
....
3162
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3176
....
3402
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3404
3405
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3408
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3416
....
3848
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3856
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3858
3859
3860
3861
3862
....
3984
3985
3986
3987
3988
3989
3990

















3991
3992
3993
3994
3995
3996
3997
....
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
....
4203
4204
4205
4206
4207
4208
4209
























4210
4211
4212
4213
4214
4215
4216
....
4234
4235
4236
4237
4238
4239
4240
4241
4242
4243
4244
4245
4246
4247
4248
4249
....
4266
4267
4268
4269
4270
4271
4272

4273
4274
4275
4276
4277
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4279
4280
4281
4282
4283
4284
4285
4286
4287
4288
....
4309
4310
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4321

4322
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4337
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4341

4342
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4351
....
4427
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....
4478
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....
4607
4608
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4622
....
4671
4672
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4679
4680
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4837
....
4847
4848
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4851
4852
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4854
4855
4856
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4906
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4922
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4925
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4954
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4977

4978
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4986
4987
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4990
4991
4992
4993
4994
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4998
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5000
5001
5002
5003
5004
5005
5006
5007
5008

5009
5010
5011
5012
5013
5014
5015
5016
5017
....
5051
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5054
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5056
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5101
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5103
5104
5105
....
5161
5162
5163
5164
5165
5166
5167
5168
5169
5170
5171
5172
5173
5174
5175
5176
5177
5178
5179
5180
5181
5182
5183
5184
5185
5186
5187
5188
5189
5190







5191

5192

5193
5194
5195
5196
5197
5198
5199

5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
5216
5217
5218
5219
5220
5221
....
5439
5440
5441
5442
5443
5444
5445
5446
5447
5448
5449
5450
5451
5452
5453
5454
5455
5456
5457
5458
....
5472
5473
5474
5475
5476
5477
5478
5479
5480
5481
5482
5483
5484
5485
5486
5487
....
5502
5503
5504
5505
5506
5507
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5510
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5514
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5516
5517
5518
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5520
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5522
5523
5524
5525
5526
5527
5528
....
5553
5554
5555
5556
5557
5558
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5560
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5562
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5567
5568
5569
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5584
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5586
5587
5588
5589
5590
5591
5592
5593
5594
5595
5596
5597
5598
....
5609
5610
5611
5612
5613
5614
5615
5616
5617
5618
5619
5620
5621
5622
5623
5624
5625
5626
5627

5628
5629
5630
5631
5632
5633
5634
5635
5636
5637
5638
....
5707
5708
5709
5710
5711
5712
5713
5714
5715
5716
5717
5718
5719
5720
5721
....
5737
5738
5739
5740
5741
5742
5743
5744
5745
5746
5747
5748
5749
5750
5751
5752
5753
5754
5755
5756
5757
5758
5759
5760
5761
5762
5763
5764
5765
5766
....
5823
5824
5825
5826
5827
5828
5829
5830
5831
5832
5833
5834
5835
5836
5837
5838
5839
5840
5841
5842
....
5867
5868
5869
5870
5871
5872
5873
5874
5875
5876
5877
5878
5879
5880
5881
5882
5883
5884
5885
5886
5887
5888
5889
5890
5891
5892
5893
5894
5895
5896
5897
5898
5899
5900
5901
5902
....
6022
6023
6024
6025
6026
6027
6028
6029
6030
6031
6032
6033
6034
6035
6036
....
6044
6045
6046
6047
6048
6049
6050
6051
6052
6053
6054
6055
6056
6057
6058
*/

#ifndef _LSM_INT_H
# include "lsmInt.h"
#endif
#include "sqlite4.h"            /* only for sqlite4_snprintf() */

#define LSM_LOG_STRUCTURE 0
#define LSM_LOG_DATA      0

/*
** Macros to help decode record types.
*/
#define rtTopic(eType)       ((eType) & LSM_SYSTEMKEY)
#define rtIsDelete(eType)    (((eType) & 0x0F)==LSM_POINT_DELETE)

#define rtIsSeparator(eType) (((eType) & LSM_SEPARATOR)!=0)
................................................................................
static void sortedBlobFree(Blob *pBlob){
  assert( pBlob->pEnv || pBlob->pData==0 );
  if( pBlob->pData ) lsmFree(pBlob->pEnv, pBlob->pData);
  memset(pBlob, 0, sizeof(Blob));
}

static int sortedReadData(
  Segment *pSeg,
  Page *pPg,
  int iOff,
  int nByte,
  void **ppData,
  Blob *pBlob
){
  int rc = LSM_OK;
................................................................................
      assert( nRem>=0 );
      if( nRem==0 ) break;
      i -= iEnd;

      /* Grab the next page in the segment */

      do {
        rc = lsmFsDbPageNext(pSeg, pPg, 1, &pNext);
        if( rc==LSM_OK && pNext==0 ){
          rc = LSM_CORRUPT_BKPT;
        }
        if( rc ) break;
        lsmFsPageRelease(pPg);
        pPg = pNext;
        aData = fsPageData(pPg, &nData);
................................................................................
  assert( iCell<pageGetNRec(aData, nData) && iCell>=0 );
  aCell = pageGetCell(aData, nData, iCell);
  lsmVarintGet64(&aCell[1], &iRet);
  return iRet;
}

static u8 *pageGetKey(
  Segment *pSeg,                  /* Segment pPg belongs to */
  Page *pPg,                      /* Page to read from */
  int iCell,                      /* Index of cell on page to read */
  int *piTopic,                   /* OUT: Topic associated with this key */
  int *pnKey,                     /* OUT: Size of key in bytes */
  Blob *pBlob                     /* If required, use this for dynamic memory */
){
  u8 *pKey;
................................................................................
  pKey += lsmVarintGet32(pKey, &nDummy);
  pKey += lsmVarintGet32(pKey, pnKey);
  if( rtIsWrite(eType) ){
    pKey += lsmVarintGet32(pKey, &nDummy);
  }
  *piTopic = rtTopic(eType);

  sortedReadData(pSeg, pPg, pKey-aData, *pnKey, (void **)&pKey, pBlob);
  return pKey;
}

static int pageGetKeyCopy(
  lsm_env *pEnv,                  /* Environment handle */
  Segment *pSeg,                  /* Segment pPg belongs to */
  Page *pPg,                      /* Page to read from */
  int iCell,                      /* Index of cell on page to read */
  int *piTopic,                   /* OUT: Topic associated with this key */
  Blob *pBlob                     /* If required, use this for dynamic memory */
){
  int rc = LSM_OK;
  int nKey;
  u8 *aKey;

  aKey = pageGetKey(pSeg, pPg, iCell, piTopic, &nKey, pBlob);
  assert( (void *)aKey!=pBlob->pData || nKey==pBlob->nData );
  if( (void *)aKey!=pBlob->pData ){
    rc = sortedBlobSet(pEnv, pBlob, aKey, nKey);
  }

  return rc;
}
................................................................................
  return iRef;
}

#define GETVARINT64(a, i) (((i)=((u8*)(a))[0])<=240?1:lsmVarintGet64((a), &(i)))
#define GETVARINT32(a, i) (((i)=((u8*)(a))[0])<=240?1:lsmVarintGet32((a), &(i)))

static int pageGetBtreeKey(
  Segment *pSeg,                  /* Segment page pPg belongs to */
  Page *pPg,
  int iKey, 
  Pgno *piPtr, 
  int *piTopic, 
  void **ppKey,
  int *pnKey,
  Blob *pBlob
................................................................................
  aCell += GETVARINT64(aCell, *piPtr);

  if( eType==0 ){
    int rc;
    Pgno iRef;                  /* Page number of referenced page */
    Page *pRef;
    aCell += GETVARINT64(aCell, iRef);
    rc = lsmFsDbPageGet(lsmPageFS(pPg), pSeg, iRef, &pRef);
    if( rc!=LSM_OK ) return rc;
    pageGetKeyCopy(lsmPageEnv(pPg), pSeg, pRef, 0, &eType, pBlob);
    lsmFsPageRelease(pRef);
    *ppKey = pBlob->pData;
    *pnKey = pBlob->nData;
  }else{
    aCell += GETVARINT32(aCell, *pnKey);
    *ppKey = aCell;
  }
................................................................................
    int iCell = pCsr->aPg[iPg].iCell;
    while( iCell<0 && (--iPg)>=0 ){
      iCell = pCsr->aPg[iPg].iCell-1;
    }
    if( iPg<0 || iCell<0 ) return LSM_CORRUPT_BKPT;

    rc = pageGetBtreeKey(
        pCsr->pSeg,
        pCsr->aPg[iPg].pPage, iCell,
        &dummy, &pCsr->eType, &pCsr->pKey, &pCsr->nKey, &pCsr->blob
    );
    pCsr->eType |= LSM_SEPARATOR;
  }

  return rc;
................................................................................
    if( pCsr->iPg>=0 ){
      pCsr->aPg[pCsr->iPg].iCell++;

      iLoad = btreeCursorPtr(aData, nData, pPg->iCell);
      do {
        Page *pLoad;
        pCsr->iPg++;
        rc = lsmFsDbPageGet(pCsr->pFS, pCsr->pSeg, iLoad, &pLoad);
        pCsr->aPg[pCsr->iPg].pPage = pLoad;
        pCsr->aPg[pCsr->iPg].iCell = 0;
        if( rc==LSM_OK ){
          if( pCsr->iPg==(pCsr->nDepth-1) ) break;
          aData = fsPageData(pLoad, &nData);
          iLoad = btreeCursorPtr(aData, nData, 0);
        }
................................................................................
  int rc;

  Page *pPg = 0;
  FileSystem *pFS = pCsr->pFS;
  int iPg = pCsr->pSeg->iRoot;

  do {
    rc = lsmFsDbPageGet(pFS, pCsr->pSeg, iPg, &pPg);
    assert( (rc==LSM_OK)==(pPg!=0) );
    if( rc==LSM_OK ){
      u8 *aData;
      int nData;
      int flags;

      aData = fsPageData(pPg, &nData);
................................................................................
  int rc = LSM_OK;

  if( p->iPg ){
    lsm_env *pEnv = lsmFsEnv(pCsr->pFS);
    int iCell;                    /* Current cell number on leaf page */
    Pgno iLeaf;                   /* Page number of current leaf page */
    int nDepth;                   /* Depth of b-tree structure */
    Segment *pSeg = pCsr->pSeg;

    /* Decode the MergeInput structure */
    iLeaf = p->iPg;
    nDepth = (p->iCell & 0x00FF);
    iCell = (p->iCell >> 8) - 1;

    /* Allocate the BtreeCursor.aPg[] array */
    assert( pCsr->aPg==0 );
    pCsr->aPg = (BtreePg *)lsmMallocZeroRc(pEnv, sizeof(BtreePg) * nDepth, &rc);

    /* Populate the last entry of the aPg[] array */
    if( rc==LSM_OK ){
      Page **pp = &pCsr->aPg[nDepth-1].pPage;
      pCsr->iPg = nDepth-1;
      pCsr->nDepth = nDepth;
      pCsr->aPg[pCsr->iPg].iCell = iCell;
      rc = lsmFsDbPageGet(pCsr->pFS, pSeg, iLeaf, pp);
    }

    /* Populate any other aPg[] array entries */
    if( rc==LSM_OK && nDepth>1 ){
      Blob blob = {0,0,0};
      void *pSeek;
      int nSeek;
      int iTopicSeek;
      int iPg = 0;
      int iLoad = pSeg->iRoot;
      Page *pPg = pCsr->aPg[nDepth-1].pPage;
 
      if( pageObjGetNRec(pPg)==0 ){
        /* This can happen when pPg is the right-most leaf in the b-tree.
        ** In this case, set the iTopicSeek/pSeek/nSeek key to a value
        ** greater than any real key.  */
        assert( iCell==-1 );
        iTopicSeek = 1000;
        pSeek = 0;
        nSeek = 0;
      }else{
        Pgno dummy;
        rc = pageGetBtreeKey(pSeg, pPg,
            0, &dummy, &iTopicSeek, &pSeek, &nSeek, &pCsr->blob
        );
      }

      do {
        Page *pPg;
        rc = lsmFsDbPageGet(pCsr->pFS, pSeg, iLoad, &pPg);
        assert( rc==LSM_OK || pPg==0 );
        if( rc==LSM_OK ){
          u8 *aData;                  /* Buffer containing page data */
          int nData;                  /* Size of aData[] in bytes */
          int iMin;
          int iMax;
          int iCell;
................................................................................
          while( iMax>=iMin ){
            int iTry = (iMin+iMax)/2;
            void *pKey; int nKey;         /* Key for cell iTry */
            int iTopic;                   /* Topic for key pKeyT/nKeyT */
            Pgno iPtr;                    /* Pointer for cell iTry */
            int res;                      /* (pSeek - pKeyT) */

            rc = pageGetBtreeKey(
                pSeg, pPg, iTry, &iPtr, &iTopic, &pKey, &nKey, &blob
            );
            if( rc!=LSM_OK ) break;

            res = sortedKeyCompare(
                xCmp, iTopicSeek, pSeek, nSeek, iTopic, pKey, nKey
            );
            assert( res!=0 );

................................................................................
              iMin = iTry+1;
            }
          }

          pCsr->aPg[iPg].pPage = pPg;
          pCsr->aPg[iPg].iCell = iCell;
          iPg++;
          assert( iPg!=nDepth-1 
               || lsmFsRedirectPage(pCsr->pFS, pSeg->pRedirect, iLoad)==iLeaf
          );
        }
      }while( rc==LSM_OK && iPg<(nDepth-1) );
      sortedBlobFree(&blob);
    }

    /* Load the current key and pointer */
    if( rc==LSM_OK ){
................................................................................
      if( pBtreePg->iCell<0 ){
        Pgno dummy;
        int i;
        for(i=pCsr->iPg-1; i>=0; i--){
          if( pCsr->aPg[i].iCell>0 ) break;
        }
        assert( i>=0 );
        rc = pageGetBtreeKey(pSeg,
            pCsr->aPg[i].pPage, pCsr->aPg[i].iCell-1,
            &dummy, &pCsr->eType, &pCsr->pKey, &pCsr->nKey, &pCsr->blob
        );
        pCsr->eType |= LSM_SEPARATOR;

      }else{
        rc = btreeCursorLoadKey(pCsr);
................................................................................
  FileSystem *pFS,
  SegmentPtr *pPtr,              /* Load page into this SegmentPtr object */
  int iNew                       /* Page number of new page */
){
  Page *pPg = 0;                 /* The new page */
  int rc;                        /* Return Code */

  rc = lsmFsDbPageGet(pFS, pPtr->pSeg, iNew, &pPg);
  assert( rc==LSM_OK || pPg==0 );
  segmentPtrSetPage(pPtr, pPg);

  return rc;
}

static int segmentPtrReadData(
  SegmentPtr *pPtr,
  int iOff,
  int nByte,
  void **ppData,
  Blob *pBlob
){
  return sortedReadData(pPtr->pSeg, pPtr->pPg, iOff, nByte, ppData, pBlob);
}

static int segmentPtrNextPage(
  SegmentPtr *pPtr,              /* Load page into this SegmentPtr object */
  int eDir                       /* +1 for next(), -1 for prev() */
){
  Page *pNext;                   /* New page to load */
................................................................................
      pPtr->pVal = 0;
    }
  }

  return rc;
}


static Segment *sortedSplitkeySegment(Level *pLevel){
  Merge *pMerge = pLevel->pMerge;
  MergeInput *p = &pMerge->splitkey;
  Segment *pSeg;
  int i;

  for(i=0; i<pMerge->nInput; i++){
    if( p->iPg==pMerge->aInput[i].iPg ) break;
  }
  if( pMerge->nInput==(pLevel->nRight+1) && i>=(pMerge->nInput-1) ){
    pSeg = &pLevel->pNext->lhs;
  }else{
    pSeg = &pLevel->aRhs[i];
  }

  return pSeg;
}

static void sortedSplitkey(lsm_db *pDb, Level *pLevel, int *pRc){
  Segment *pSeg;
  Page *pPg = 0;
  lsm_env *pEnv = pDb->pEnv;      /* Environment handle */
  int rc = *pRc;
  Merge *pMerge = pLevel->pMerge;

  pSeg = sortedSplitkeySegment(pLevel);
  if( rc==LSM_OK ){
    rc = lsmFsDbPageGet(pDb->pFS, pSeg, pMerge->splitkey.iPg, &pPg);
  }
  if( rc==LSM_OK ){
    int iTopic;
    Blob blob = {0, 0, 0, 0};
    u8 *aData;
    int nData;
  
    aData = lsmFsPageData(pPg, &nData);
    if( pageGetFlags(aData, nData) & SEGMENT_BTREE_FLAG ){
      void *pKey;
      int nKey;
      Pgno dummy;
      rc = pageGetBtreeKey(pSeg,
          pPg, pMerge->splitkey.iCell, &dummy, &iTopic, &pKey, &nKey, &blob
      );
      if( rc==LSM_OK && blob.pData!=pKey ){
        rc = sortedBlobSet(pEnv, &blob, pKey, nKey);
      }
    }else{
      rc = pageGetKeyCopy(
          pEnv, pSeg, pPg, pMerge->splitkey.iCell, &iTopic, &blob
      );
    }

    pLevel->iSplitTopic = iTopic;
    pLevel->pSplitKey = blob.pData;
    pLevel->nSplitKey = blob.nData;
    lsmFsPageRelease(pPg);
  }
................................................................................
    if( svFlags && pPtr->pPg ){
      int res = sortedKeyCompare(pCsr->pDb->xCmp,
          rtTopic(pPtr->eType), pPtr->pKey, pPtr->nKey,
          pLvl->iSplitTopic, pLvl->pSplitKey, pLvl->nSplitKey
      );
      if( res<0 ) segmentPtrReset(pPtr);
    }

    if( pPtr->pPg==0 && (svFlags & LSM_END_DELETE) ){
      Segment *pSeg = pPtr->pSeg;
      rc = lsmFsDbPageGet(pCsr->pDb->pFS, pSeg, pSeg->iFirst, &pPtr->pPg);
      if( rc!=LSM_OK ) return rc;
      pPtr->eType = LSM_START_DELETE | LSM_POINT_DELETE;
      pPtr->eType |= (pLvl->iSplitTopic ? LSM_SYSTEMKEY : 0);
      pPtr->pKey = pLvl->pSplitKey;
      pPtr->nKey = pLvl->nSplitKey;
    }

  }while( pCsr 
       && pPtr->pPg 
       && segmentPtrIgnoreSeparators(pCsr, pPtr)
................................................................................
static void segmentPtrEndPage(
  FileSystem *pFS, 
  SegmentPtr *pPtr, 
  int bLast, 
  int *pRc
){
  if( *pRc==LSM_OK ){
    Segment *pSeg = pPtr->pSeg;
    Page *pNew = 0;
    if( bLast ){
      *pRc = lsmFsDbPageLast(pFS, pSeg, &pNew);
    }else{
      *pRc = lsmFsDbPageGet(pFS, pSeg, pSeg->iFirst, &pNew);
    }
    segmentPtrSetPage(pPtr, pNew);
  }
}


/*
................................................................................
      && (pPtr->nCell==0 || (pPtr->flags & SEGMENT_BTREE_FLAG))
  ){
    rc = segmentPtrNextPage(pPtr, (bLast ? -1 : 1));
  }

  if( rc==LSM_OK && pPtr->pPg ){
    rc = segmentPtrLoadCell(pPtr, bLast ? (pPtr->nCell-1) : 0);
    if( rc==LSM_OK && bLast && pPtr->pSeg!=&pLvl->lhs ){
      int res = sortedKeyCompare(pCsr->pDb->xCmp,
          rtTopic(pPtr->eType), pPtr->pKey, pPtr->nKey,
          pLvl->iSplitTopic, pLvl->pSplitKey, pLvl->nSplitKey
      );
      if( res<0 ) segmentPtrReset(pPtr);
    }
  }
  
  bIgnore = segmentPtrIgnoreSeparators(pCsr, pPtr);
  if( rc==LSM_OK && pPtr->pPg && bIgnore && rtIsSeparator(pPtr->eType) ){
    rc = segmentPtrAdvance(pCsr, pPtr, bLast);
  }

#if 0
  if( bLast && rc==LSM_OK && pPtr->pPg
   && pPtr->pSeg==&pLvl->lhs 
   && pLvl->nRight && (pPtr->eType & LSM_START_DELETE)
  ){
    pPtr->iCell++;
    pPtr->eType = LSM_END_DELETE | (pLvl->iSplitTopic);
    pPtr->pKey = pLvl->pSplitKey;
    pPtr->nKey = pLvl->nSplitKey;
    pPtr->pVal = 0;
    pPtr->nVal = 0;
  }
#endif

  return rc;
}

static void segmentPtrKey(SegmentPtr *pPtr, void **ppKey, int *pnKey){
  assert( pPtr->pPg );
  *ppKey = pPtr->pKey;
................................................................................
  int iTopic = 0;                 /* TODO: Fix me */

  for(eDir=-1; eDir<=1; eDir+=2){
    Page *pTest = pPtr->pPg;

    lsmFsPageRef(pTest);
    while( pTest ){
      Segment *pSeg = pPtr->pSeg;
      Page *pNext;

      int rc = lsmFsDbPageNext(pSeg, pTest, eDir, &pNext);
      lsmFsPageRelease(pTest);
      if( rc ) return 1;
      pTest = pNext;

      if( pTest ){
        int nData;
        u8 *aData = fsPageData(pTest, &nData);
................................................................................
          int nPgKey;
          int iPgTopic;
          u8 *pPgKey;
          int res;
          int iCell;

          iCell = ((eDir < 0) ? (nCell-1) : 0);
          pPgKey = pageGetKey(pSeg, pTest, iCell, &iPgTopic, &nPgKey, &blob);
          res = iTopic - iPgTopic;
          if( res==0 ) res = pCsr->pDb->xCmp(pKey, nKey, pPgKey, nPgKey);
          if( (eDir==1 && res>0) || (eDir==-1 && res<0) ){
            /* Taking this branch means something has gone wrong. */
            char *zMsg = lsmMallocPrintf(pEnv, "Key \"%s\" is not on page %d", 
                keyToString(pEnv, pKey, nKey), lsmFsPageNumber(pPtr->pPg)
            );
................................................................................
    u8 *pLastKey;
    int nLastKey;
    int iLastTopic;
    int res;                      /* Result of comparison */
    Page *pNext;

    /* Load the last key on the current page. */
    pLastKey = pageGetKey(pPtr->pSeg,
        pPtr->pPg, pPtr->nCell-1, &iLastTopic, &nLastKey, &pPtr->blob1
    );

    /* If the loaded key is >= than (pKey/nKey), break out of the loop.
    ** If (pKey/nKey) is present in this array, it must be on the current 
    ** page.  */
    res = sortedKeyCompare(
................................................................................
  do {
    Pgno *piFirst = 0;
    if( aPg ){
      aPg[i++] = iPg;
      piFirst = &aPg[i];
    }

    rc = lsmFsDbPageGet(pCsr->pDb->pFS, pSeg, iPg, &pPg);
    assert( rc==LSM_OK || pPg==0 );
    if( rc==LSM_OK ){
      u8 *aData;                  /* Buffer containing page data */
      int nData;                  /* Size of aData[] in bytes */
      int iMin;
      int iMax;
      int nRec;
................................................................................
      while( iMax>=iMin ){
        int iTry = (iMin+iMax)/2;
        void *pKeyT; int nKeyT;       /* Key for cell iTry */
        int iTopicT;                  /* Topic for key pKeyT/nKeyT */
        Pgno iPtr;                    /* Pointer associated with cell iTry */
        int res;                      /* (pKey - pKeyT) */

        rc = pageGetBtreeKey(
            pSeg, pPg, iTry, &iPtr, &iTopicT, &pKeyT, &nKeyT, &blob
        );
        if( rc!=LSM_OK ) break;
        if( piFirst && pKeyT==blob.pData ){
          *piFirst = pageGetBtreeRef(pPg, iTry);
          piFirst = 0;
          i++;
        }

................................................................................
    );
    if( rc==LSM_OK && nRhs>0 && eSeek==LSM_SEEK_GE && aPtr[0].pPg==0 ){
      res = 0;
    }
  }
  
  if( res>=0 ){
    int bHit = 0;                 /* True if at least one rhs is not EOF */
    int iPtr = *piPgno;
    int i;
    for(i=1; rc==LSM_OK && i<=nRhs && bStop==0; i++){
      SegmentPtr *pPtr = &aPtr[i];
      iOut = 0;
      rc = seekInSegment(
          pCsr, pPtr, iTopic, pKey, nKey, iPtr, eSeek, &iOut, &bStop
      );
      iPtr = iOut;

      /* If the segment-pointer has settled on a key that is smaller than
      ** the splitkey, invalidate the segment-pointer.  */
      if( pPtr->pPg ){
        res = sortedKeyCompare(pCsr->pDb->xCmp, 
            rtTopic(pPtr->eType), pPtr->pKey, pPtr->nKey, 
            pLvl->iSplitTopic, pLvl->pSplitKey, pLvl->nSplitKey
        );
        if( res<0 ) segmentPtrReset(pPtr);
      }

      if( aPtr[i].pKey ) bHit = 1;
    }

    if( rc==LSM_OK && eSeek==LSM_SEEK_LE && bHit==0 ){
      rc = segmentPtrEnd(pCsr, &aPtr[0], 1);
    }
  }

  assert( eSeek==LSM_SEEK_EQ || bStop==0 );
  *piPgno = iOut;
  *pbStop = bStop;
................................................................................
  MultiCursor *pCsr, 
  int iPtr,
  int bReverse
){
  int rc;
  SegmentPtr *pPtr = &pCsr->aPtr[iPtr];
  Level *pLvl = pPtr->pLevel;
  int bComposite;                 /* True if pPtr is part of composite level */

  /* Advance the segment-pointer object. */
  rc = segmentPtrAdvance(pCsr, pPtr, bReverse);
  if( rc!=LSM_OK ) return rc;

  bComposite = (pLvl->nRight>0 && pCsr->nPtr>pLvl->nRight);
  if( bComposite && pPtr->pPg==0 ){
    int bFix = 0;
    if( (bReverse==0)==(pPtr->pSeg==&pLvl->lhs) ){
      int i;
      if( bReverse ){
        SegmentPtr *pLhs = &pCsr->aPtr[iPtr - 1 - (pPtr->pSeg - pLvl->aRhs)];
        for(i=0; i<pLvl->nRight; i++){
          if( pLhs[i+1].pPg ) break;
        }
        if( i==pLvl->nRight ){
          bFix = 1;
          rc = segmentPtrEnd(pCsr, pLhs, 1);
        }
      }else{
        bFix = 1;
        for(i=0; rc==LSM_OK && i<pLvl->nRight; i++){
          rc = sortedRhsFirst(pCsr, pLvl, &pCsr->aPtr[iPtr+1+i]);
        }
      }
    }

    if( bFix ){
      int i;
      for(i=pCsr->nTree-1; i>0; i--){
        multiCursorDoCompare(pCsr, i, bReverse);
      }
    }
  }

#if 0
  if( bComposite && pPtr->pSeg==&pLvl->lhs       /* lhs of composite level */
   && bReverse==0                                /* csr advanced forwards */
   && pPtr->pPg==0                               /* segment at EOF */
  ){
    int i;
    for(i=0; rc==LSM_OK && i<pLvl->nRight; i++){
      rc = sortedRhsFirst(pCsr, pLvl, &pCsr->aPtr[iPtr+1+i]);
    }
    for(i=pCsr->nTree-1; i>0; i--){
      multiCursorDoCompare(pCsr, i, 0);
    }
  }
#endif

  return rc;
}

static void mcursorFreeComponents(MultiCursor *pCsr){
  int i;
  lsm_env *pEnv = pCsr->pDb->pEnv;
................................................................................
  for(i=0; i<nRhs; i++){
    pCsr->aPtr[i].pSeg = &pLvl->aRhs[i];
    pCsr->aPtr[i].pLevel = pLvl;
  }

  return LSM_OK;
}

static void multiCursorAddOne(MultiCursor *pCsr, Level *pLvl, int *pRc){
  if( *pRc==LSM_OK ){
    int iPtr = pCsr->nPtr;
    int i;
    pCsr->aPtr[iPtr].pLevel = pLvl;
    pCsr->aPtr[iPtr].pSeg = &pLvl->lhs;
    iPtr++;
    for(i=0; i<pLvl->nRight; i++){
      pCsr->aPtr[iPtr].pLevel = pLvl;
      pCsr->aPtr[iPtr].pSeg = &pLvl->aRhs[i];
      iPtr++;
    }

    if( pLvl->nRight && pLvl->pSplitKey==0 ){
      sortedSplitkey(pCsr->pDb, pLvl, pRc);
    }
    pCsr->nPtr = iPtr;
  }
}

static int multiCursorAddAll(MultiCursor *pCsr, Snapshot *pSnap){
  Level *pLvl;
  int nPtr = 0;
  int iPtr = 0;
  int rc = LSM_OK;

................................................................................
    ** complete level may confuse it.  */
    if( pLvl->flags & LEVEL_INCOMPLETE ) continue;
    nPtr += (1 + pLvl->nRight);
  }

  assert( pCsr->aPtr==0 );
  pCsr->aPtr = lsmMallocZeroRc(pCsr->pDb->pEnv, sizeof(SegmentPtr) * nPtr, &rc);


  for(pLvl=pSnap->pLevel; pLvl; pLvl=pLvl->pNext){

    if( (pLvl->flags & LEVEL_INCOMPLETE)==0 ){











      multiCursorAddOne(pCsr, pLvl, &rc);
    }
  }

  return rc;
}

static int multiCursorInit(MultiCursor *pCsr, Snapshot *pSnap){
................................................................................
  void *pCtx                      /* First argument to pass to callback */
){
  MultiCursor *pCsr;              /* Cursor used to read db */
  int rc = LSM_OK;                /* Return Code */
  Snapshot *pSnap = 0;

  assert( pDb->pWorker );
  if( pDb->bIncrMerge ){
    rc = lsmCheckpointDeserialize(pDb, 0, pDb->pShmhdr->aSnap1, &pSnap);
    if( rc!=LSM_OK ) return rc;
  }else{
    pSnap = pDb->pWorker;
  }

  pCsr = multiCursorNew(pDb, &rc);
  if( pCsr ){
    rc = multiCursorAddAll(pCsr, pSnap);
    pCsr->flags |= CURSOR_IGNORE_DELETE;
  }
  
................................................................................
        if( x(pCtx, iBlk, iSnap) ) break;
        rc = multiCursorAdvance(pCsr, !bReverse);
      }
    }
  }

  lsmMCursorClose(pCsr);
  if( pSnap!=pDb->pWorker ){
    lsmFreeSnapshot(pDb->pEnv, pSnap);
  }

  return rc;
}

int lsmSortedLoadFreelist(
  lsm_db *pDb,                    /* Database handle (must be worker) */
  void **ppVal,                   /* OUT: Blob containing LSM free-list */
................................................................................
  if( *pRc==LSM_OK ){
    void *pKey;
    int nKey;
    multiCursorGetKey(pCsr, pCsr->aTree[1], &pCsr->eType, &pKey, &nKey);
    *pRc = sortedBlobSet(pCsr->pDb->pEnv, &pCsr->key, pKey, nKey);
  }
}

#ifndef NDEBUG
static void assertCursorTree(MultiCursor *pCsr){
  int bRev = !!(pCsr->flags & CURSOR_PREV_OK);
  int *aSave = pCsr->aTree;
  int nSave = pCsr->nTree;
  int rc;

  pCsr->aTree = 0;
  pCsr->nTree = 0;
  rc = multiCursorAllocTree(pCsr);
  if( rc==LSM_OK ){
    int i;
    for(i=pCsr->nTree-1; i>0; i--){
      multiCursorDoCompare(pCsr, i, bRev);
    }

    assert( nSave==pCsr->nTree 
        && 0==memcmp(aSave, pCsr->aTree, sizeof(int)*nSave)
    );

    lsmFree(pCsr->pDb->pEnv, pCsr->aTree);
  }

  pCsr->aTree = aSave;
  pCsr->nTree = nSave;
}
#else
# define assertCursorTree(x)
#endif

static int mcursorLocationOk(MultiCursor *pCsr, int bDeleteOk){
  int eType = pCsr->eType;
  int iKey;
  int i;
  int rdmask;
  
  assert( pCsr->flags & (CURSOR_NEXT_OK|CURSOR_PREV_OK) );
  assertCursorTree(pCsr);




  rdmask = (pCsr->flags & CURSOR_NEXT_OK) ? LSM_END_DELETE : LSM_START_DELETE;

  /* If the cursor does not currently point to an actual database key (i.e.
  ** it points to a delete key, or the start or end of a range-delete), and
  ** the CURSOR_IGNORE_DELETE flag is set, skip past this entry.  */
  if( (pCsr->flags & CURSOR_IGNORE_DELETE) && bDeleteOk==0 ){
    if( (eType & LSM_INSERT)==0 ) return 0;
  }

  /* If the cursor points to a system key (free-list entry), and the
  ** CURSOR_IGNORE_SYSTEM flag is set, skip thie entry.  */
  if( (pCsr->flags & CURSOR_IGNORE_SYSTEM) && rtTopic(eType)!=0 ){
    return 0;
  }

#ifndef NDEBUG
  /* This block fires assert() statements to check one of the assumptions
  ** in the comment below - that if the lhs sub-cursor of a level undergoing
  ** a merge is valid, then all the rhs sub-cursors must be at EOF. 
  **
  ** Also assert that all rhs sub-cursors are either at EOF or point to
  ** a key that is not less than the level split-key.  */
  for(i=0; i<pCsr->nPtr; i++){
    SegmentPtr *pPtr = &pCsr->aPtr[i];
    Level *pLvl = pPtr->pLevel;
    if( pLvl->nRight && pPtr->pPg ){
      if( pPtr->pSeg==&pLvl->lhs ){
        int j;
        for(j=0; j<pLvl->nRight; j++) assert( pPtr[j+1].pPg==0 );
      }else{
        int res = sortedKeyCompare(pCsr->pDb->xCmp, 
            rtTopic(pPtr->eType), pPtr->pKey, pPtr->nKey,
            pLvl->iSplitTopic, pLvl->pSplitKey, pLvl->nSplitKey
        );
        assert( res>=0 );
      }
    }
  }
#endif

  /* Now check if this key has already been deleted by a range-delete. If 
  ** so, skip past it.
  **
  ** Assume, for the moment, that the tree contains no levels currently 
  ** undergoing incremental merge, and that this cursor is iterating forwards
  ** through the database keys. The cursor currently points to a key in
  ** level L. This key has already been deleted if any of the sub-cursors
  ** that point to levels newer than L (or to the in-memory tree) point to
  ** a key greater than the current key with the LSM_END_DELETE flag set.
  **
  ** Or, if the cursor is iterating backwards through data keys, if any
  ** such sub-cursor points to a key smaller than the current key with the
  ** LSM_START_DELETE flag set.
  **
  ** Why it works with levels undergoing a merge too:
  **
  ** When a cursor iterates forwards, the sub-cursors for the rhs of a 
  ** level are only activated once the lhs reaches EOF. So when iterating
  ** forwards, the keys visited are the same as if the level was completely
  ** merged.
  **
  ** If the cursor is iterating backwards, then the lhs sub-cursor is not 
  ** initialized until the last of the rhs sub-cursors has reached EOF.
  ** Additionally, if the START_DELETE flag is set on the last entry (in
  ** reverse order - so the entry with the smallest key) of a rhs sub-cursor,
  ** then a pseudo-key equal to the levels split-key with the END_DELETE
  ** flag set is visited by the sub-cursor.
  */ 
  iKey = pCsr->aTree[1];
  for(i=0; i<iKey; i++){
    int csrflags;
    multiCursorGetKey(pCsr, i, &csrflags, 0, 0);
    if( (rdmask & csrflags) ){
      const int SD_ED = (LSM_START_DELETE|LSM_END_DELETE);
      if( (csrflags & SD_ED)==SD_ED 
................................................................................
          continue;
        }
      }
      return 0;
    }
  }

  /* The current cursor position is one this cursor should visit. Return 1. */



  return 1;
}


static int multiCursorSetupTree(MultiCursor *pCsr, int bRev){
  int rc;

  rc = multiCursorAllocTree(pCsr);
  if( rc==LSM_OK ){
    int i;
    for(i=pCsr->nTree-1; i>0; i--){
      multiCursorDoCompare(pCsr, i, bRev);
    }
  }





  assertCursorTree(pCsr);
  multiCursorCacheKey(pCsr, &rc);

  if( rc==LSM_OK && mcursorLocationOk(pCsr, 0)==0 ){
    rc = multiCursorAdvance(pCsr, bRev);
  }
  return rc;
}


static int multiCursorEnd(MultiCursor *pCsr, int bLast){
  int rc = LSM_OK;
  int i;

  pCsr->flags &= ~(CURSOR_NEXT_OK | CURSOR_PREV_OK);
  pCsr->flags |= (bLast ? CURSOR_PREV_OK : CURSOR_NEXT_OK);
  pCsr->iFree = 0;

  /* Position the two in-memory tree cursors */
  for(i=0; rc==LSM_OK && i<2; i++){
    if( pCsr->apTreeCsr[i] ){
      rc = lsmTreeCursorEnd(pCsr->apTreeCsr[i], bLast);
    }


  }



  for(i=0; rc==LSM_OK && i<pCsr->nPtr; i++){
    SegmentPtr *pPtr = &pCsr->aPtr[i];
    Level *pLvl = pPtr->pLevel;
    int iRhs;
    int bHit = 0;

    if( bLast ){
      for(iRhs=0; iRhs<pLvl->nRight && rc==LSM_OK; iRhs++){
        rc = segmentPtrEnd(pCsr, &pPtr[iRhs+1], 1);
        if( pPtr[iRhs+1].pPg ) bHit = 1;
      }
      if( bHit==0 && rc==LSM_OK ){
        rc = segmentPtrEnd(pCsr, pPtr, 1);
      }else{
        segmentPtrReset(pPtr);
      }
    }else{
      int bLhs = (pPtr->pSeg==&pLvl->lhs);



      assert( pPtr->pSeg==&pLvl->lhs || pPtr->pSeg==&pLvl->aRhs[0] );

      if( bLhs ){
        rc = segmentPtrEnd(pCsr, pPtr, 0);
        if( pPtr->pKey ) bHit = 1;

      }
      for(iRhs=0; iRhs<pLvl->nRight && rc==LSM_OK; iRhs++){
        if( bHit ){
          segmentPtrReset(&pPtr[iRhs+1]);
        }else{

          rc = sortedRhsFirst(pCsr, pLvl, &pPtr[iRhs+bLhs]);
        }
      }
    }
    i += pLvl->nRight;
  }


  /* And the b-tree cursor, if applicable */
  if( rc==LSM_OK && pCsr->pBtCsr ){
    assert( bLast==0 );
    rc = btreeCursorFirst(pCsr->pBtCsr);
  }

  if( rc==LSM_OK ){
    rc = multiCursorSetupTree(pCsr, bLast);
  }



  











  return rc;
}


int mcursorSave(MultiCursor *pCsr){
  int rc = LSM_OK;
  if( pCsr->aTree ){
................................................................................

    /* If this cursor is configured to skip deleted keys, and the current
    ** cursor points to a SORTED_DELETE entry, then the cursor has not been 
    ** successfully advanced.  
    **
    ** Similarly, if the cursor is configured to skip system keys and the
    ** current cursor points to a system key, it has not yet been advanced.
    */
    if( *pRc==LSM_OK && 0==mcursorLocationOk(pCsr, 0) ) return 0;
  }
  return 1;
}

static void flCsrAdvance(MultiCursor *pCsr){
  assert( pCsr->flags & CURSOR_FLUSH_FREELIST );
................................................................................
}

static int multiCursorAdvance(MultiCursor *pCsr, int bReverse){
  int rc = LSM_OK;                /* Return Code */
  if( lsmMCursorValid(pCsr) ){
    do {
      int iKey = pCsr->aTree[1];

      assertCursorTree(pCsr);

      /* If this multi-cursor is advancing forwards, and the sub-cursor
      ** being advanced is the one that separator keys may be being read
      ** from, record the current absolute pointer value.  */
      if( pCsr->pPrevMergePtr ){
        if( iKey==(CURSOR_DATA_SEGMENT+pCsr->nPtr) ){
          assert( pCsr->pBtCsr );
................................................................................
        rc = segmentCursorAdvance(pCsr, iKey-CURSOR_DATA_SEGMENT, bReverse);
      }
      if( rc==LSM_OK ){
        int i;
        for(i=(iKey+pCsr->nTree)/2; i>0; i=i/2){
          multiCursorDoCompare(pCsr, i, bReverse);
        }
        assertCursorTree(pCsr);
      }
    }while( mcursorAdvanceOk(pCsr, bReverse, &rc)==0 );
  }
  return rc;
}

int lsmMCursorNext(MultiCursor *pCsr){
................................................................................

    do {
      Page *pPg = 0;
      u8 *aData;
      int nData;
      int flags;

      rc = lsmFsDbPageGet(pFS, pSeg, iPg, &pPg);
      if( rc!=LSM_OK ) break;

      aData = fsPageData(pPg, &nData);
      flags = pageGetFlags(aData, nData);
      if( flags&SEGMENT_BTREE_FLAG ){
        Page **apNew = (Page **)lsmRealloc(
            pEnv, apHier, sizeof(Page *)*(nHier+1)
................................................................................

  if( pCsr->pBtCsr ){
    rc = LSM_OK;
    iFPtr = pMW->pLevel->pNext->lhs.iFirst;
  }else if( pCsr->nPtr>0 ){
    Segment *pSeg;
    pSeg = pCsr->aPtr[pCsr->nPtr-1].pSeg;
    rc = lsmFsDbPageGet(pMW->pDb->pFS, pSeg, pSeg->iFirst, &pPg);
    if( rc==LSM_OK ){
      u8 *aData;                    /* Buffer for page pPg */
      int nData;                    /* Size of aData[] in bytes */
      aData = fsPageData(pPg, &nData);
      iFPtr = pageGetPtr(aData, nData);
      lsmFsPageRelease(pPg);
    }
................................................................................
    }
  }

  return rc;
}



















/*
** Free all resources allocated by mergeWorkerInit().
*/
static void mergeWorkerShutdown(MergeWorker *pMW, int *pRc){
  int i;                          /* Iterator variable */
  int rc = *pRc;
  MultiCursor *pCsr = pMW->pCsr;
................................................................................

  iVal = pCsr->aTree[1];
  mergeRangeDeletes(pCsr, &iVal, &eType);

  if( eType!=0 ){
    if( pMW->aGobble ){
      int iGobble = pCsr->aTree[1] - CURSOR_DATA_SEGMENT;
      if( iGobble<pCsr->nPtr && iGobble>=0 ){
        SegmentPtr *pGobble = &pCsr->aPtr[iGobble];
        if( (pGobble->flags & PGFTR_SKIP_THIS_FLAG)==0 ){
          pMW->aGobble[iGobble] = lsmFsPageNumber(pGobble->pPg);
        }
      }
    }

................................................................................
    }
  }

  /* Advance the cursor to the next input record (assuming one exists). */
  assert( lsmMCursorValid(pMW->pCsr) );
  if( rc==LSM_OK ) rc = lsmMCursorNext(pMW->pCsr);

























  return rc;
}

static int mergeWorkerDone(MergeWorker *pMW){
  return pMW->pCsr==0 || !lsmMCursorValid(pMW->pCsr);
}

................................................................................
  int eTree,                      /* One of the TREE_XXX constants */
  int *pnWrite                    /* OUT: Number of database pages written */
){
  int rc = LSM_OK;                /* Return Code */
  MultiCursor *pCsr = 0;
  Level *pNext = 0;               /* The current top level */
  Level *pNew;                    /* The new level itself */
  Segment *pLinked = 0;           /* Delete separators from this segment */
  Level *pDel = 0;                /* Delete this entire level */
  int nWrite = 0;                 /* Number of database pages written */
  Freelist freelist;

  if( eTree!=TREE_NONE ){
    rc = lsmShmCacheChunks(pDb, pDb->treehdr.nChunk);
  }

................................................................................
  pCsr = multiCursorNew(pDb, &rc);
  if( pCsr ){
    pCsr->pDb = pDb;
    rc = multiCursorVisitFreelist(pCsr);
    if( rc==LSM_OK ){
      rc = multiCursorAddTree(pCsr, pDb->pWorker, eTree);
    }

    if( rc==LSM_OK && pNext && pNext->pMerge==0 ){
      if( (pNext->flags & LEVEL_FREELIST_ONLY) ){
        pDel = pNext;
        pCsr->aPtr = lsmMallocZeroRc(pDb->pEnv, sizeof(SegmentPtr), &rc);
        multiCursorAddOne(pCsr, pNext, &rc);
      }else if( eTree!=TREE_NONE && pNext->lhs.iRoot ){
        pLinked = &pNext->lhs;
        rc = btreeCursorNew(pDb, pLinked, &pCsr->pBtCsr);
      }
    }

    /* If this will be the only segment in the database, discard any delete
    ** markers present in the in-memory tree.  */
    if( pNext==0 ){
      multiCursorIgnoreDelete(pCsr);
    }
................................................................................
    mergeworker.bFlush = 1;

    /* Do the work to create the new merged segment on disk */
    if( rc==LSM_OK ) rc = lsmMCursorFirst(pCsr);
    while( rc==LSM_OK && mergeWorkerDone(&mergeworker)==0 ){
      rc = mergeWorkerStep(&mergeworker);
    }
    mergeWorkerShutdown(&mergeworker, &rc);
    assert( rc!=LSM_OK || mergeworker.nWork==0 || pNew->lhs.iFirst );
    if( rc==LSM_OK && pNew->lhs.iFirst ){
      rc = lsmFsSortedFinish(pDb->pFS, &pNew->lhs);
    }
    nWrite = mergeworker.nWork;

    pNew->flags &= ~LEVEL_INCOMPLETE;
    if( eTree==TREE_NONE ){
      pNew->flags |= LEVEL_FREELIST_ONLY;
    }
    pNew->pMerge = 0;
  }

  if( rc!=LSM_OK || pNew->lhs.iFirst==0 ){
    assert( rc!=LSM_OK || pDb->pWorker->freelist.nEntry==0 );
    lsmDbSnapshotSetLevel(pDb->pWorker, pNext);
    sortedFreeLevel(pDb->pEnv, pNew);
  }else{
    if( pLinked ){
      pLinked->iRoot = 0;
    }else if( pDel ){
      assert( pNew->pNext==pDel );
      pNew->pNext = pDel->pNext;
      lsmFsSortedDelete(pDb->pFS, pDb->pWorker, 1, &pDel->lhs);
      sortedFreeLevel(pDb->pEnv, pDel);
    }


#if LSM_LOG_STRUCTURE
    lsmSortedDumpStructure(pDb, pDb->pWorker, LSM_LOG_DATA, 0, "new-toplevel");
#endif

    if( freelist.nEntry ){
      Freelist *p = &pDb->pWorker->freelist;
      lsmFree(pDb->pEnv, p->aEntry);
      memcpy(p, &freelist, sizeof(freelist));
      freelist.aEntry = 0;
................................................................................
    pTopLevel = lsmDbSnapshotLevel(pDb->pWorker);
    pNew->pNext = p;
    for(pp=&pTopLevel; *pp!=pLevel; pp=&((*pp)->pNext));
    *pp = pNew;
    lsmDbSnapshotSetLevel(pDb->pWorker, pTopLevel);

    /* Determine whether or not the next separators will be linked in */
    if( pNext && pNext->pMerge==0 && pNext->lhs.iRoot && pNext 
     && (bFreeOnly==0 || (pNext->flags & LEVEL_FREELIST_ONLY))
    ){
      bUseNext = 1;
    }
  }

  /* Allocate the merge object */
  nByte = sizeof(Merge) + sizeof(MergeInput) * (nMerge + bUseNext);
  pMerge = (Merge *)lsmMallocZeroRc(pDb->pEnv, nByte, &rc);
................................................................................
  **      separators attached to the LHS of the following level, or neither.
  **
  ** If the new level is the lowest (oldest) in the db, discard any
  ** delete keys. Key annihilation.
  */
  pCsr = multiCursorNew(pDb, &rc);
  if( pCsr ){
    pCsr->flags |= CURSOR_NEXT_OK;
    rc = multiCursorAddRhs(pCsr, pLevel);
  }
  if( rc==LSM_OK && pMerge->nInput > pLevel->nRight ){
    rc = btreeCursorNew(pDb, &pNext->lhs, &pCsr->pBtCsr);
  }else if( pNext ){
    multiCursorReadSeparators(pCsr);
  }else{
................................................................................
  ** with the largest number of right-hand segments. Work on it. */
  for(pLevel=pTopLevel; pLevel; pLevel=pLevel->pNext){
    if( pLevel->nRight==0 && pThis && pLevel->iAge==pThis->iAge ){
      nThis++;
    }else{
      if( nThis>nBest ){
        if( (pLevel->iAge!=pThis->iAge+1)
         || (pLevel->nRight==0 && sortedCountLevels(pLevel)<=pDb->nMerge)
        ){
          pBest = pThis;
          nBest = nThis;
        }
      }
      if( pLevel->nRight ){
        if( pLevel->nRight>nBest ){
          nBest = pLevel->nRight;
................................................................................
  if( pTop && pTop->iAge==0
   && (pTop->nRight || sortedCountLevels(pTop)>=pDb->nMerge)
  ){
    return 1;
  }
  return 0;
}

typedef struct MoveBlockCtx MoveBlockCtx;
struct MoveBlockCtx {
  int iSeen;                      /* Previous free block on list */
  int iFrom;                      /* Total number of blocks in file */
};

static int moveBlockCb(void *pCtx, int iBlk, i64 iSnapshot){
  MoveBlockCtx *p = (MoveBlockCtx *)pCtx;
  assert( p->iFrom==0 );
  if( iBlk==(p->iSeen-1) ){
    p->iSeen = iBlk;
    return 0;
  }
  p->iFrom = p->iSeen-1;
  return 1;
}

/*
** This function is called to further compact a database for which all 
** of the content has already been merged into a single segment. If 
** possible, it moves the contents of a single block from the end of the
** file to a free-block that lies closer to the start of the file (allowing
** the file to be eventually truncated).
*/
static int sortedMoveBlock(lsm_db *pDb, int *pnWrite){
  Snapshot *p = pDb->pWorker;
  Level *pLvl = lsmDbSnapshotLevel(p);
  int iFrom;                      /* Block to move */
  int iTo;                        /* Destination to move block to */
  int rc;                         /* Return code */

  MoveBlockCtx sCtx;

  assert( pLvl->pNext==0 && pLvl->nRight==0 );
  assert( p->redirect.n<=LSM_MAX_BLOCK_REDIRECTS );

  *pnWrite = 0;

  /* Check that the redirect array is not already full. If it is, return
  ** without moving any database content.  */
  if( p->redirect.n>=LSM_MAX_BLOCK_REDIRECTS ) return LSM_OK;

  /* Find the last block of content in the database file. Do this by 
  ** traversing the free-list in reverse (descending block number) order.
  ** The first block not on the free list is the one that will be moved.
  ** Since the db consists of a single segment, there is no ambiguity as
  ** to which segment the block belongs to.  */
  sCtx.iSeen = p->nBlock+1;
  sCtx.iFrom = 0;
  rc = lsmWalkFreelist(pDb, 1, moveBlockCb, &sCtx);
  if( rc!=LSM_OK || sCtx.iFrom==0 ) return rc;
  iFrom = sCtx.iFrom;

  /* Find the first free block in the database, ignoring block 1. Block
  ** 1 is tricky as it is smaller than the other blocks.  */
  rc = lsmBlockAllocate(pDb, iFrom, &iTo);
  if( rc!=LSM_OK || iTo==0 ) return rc;
  assert( iTo!=1 && iTo<iFrom );

  rc = lsmFsMoveBlock(pDb->pFS, &pLvl->lhs, iTo, iFrom);
  if( rc==LSM_OK ){
    if( p->redirect.a==0 ){
      int nByte = sizeof(struct RedirectEntry) * LSM_MAX_BLOCK_REDIRECTS;
      p->redirect.a = lsmMallocZeroRc(pDb->pEnv, nByte, &rc);
    }
    if( rc==LSM_OK ){
      memmove(&p->redirect.a[1], &p->redirect.a[0], 
          sizeof(struct RedirectEntry) * p->redirect.n
      );
      p->redirect.a[0].iFrom = iFrom;
      p->redirect.a[0].iTo = iTo;
      p->redirect.n++;

      rc = lsmBlockFree(pDb, iFrom);

      *pnWrite = lsmFsBlockSize(pDb->pFS) / lsmFsPageSize(pDb->pFS);
      pLvl->lhs.pRedirect = &p->redirect;
    }
  }

#if LSM_LOG_STRUCTURE
  if( rc==LSM_OK ){
    char aBuf[64];
    sprintf(aBuf, "move-block %d/%d", p->redirect.n-1, LSM_MAX_BLOCK_REDIRECTS);
    lsmSortedDumpStructure(pDb, pDb->pWorker, LSM_LOG_DATA, 0, aBuf);
  }
#endif
  return rc;
}

/*
*/
static int mergeInsertFreelistSegments(
  lsm_db *pDb, 
  int nFree,
  MergeWorker *pMW
){
  int rc = LSM_OK;
  if( nFree>0 ){
    MultiCursor *pCsr = pMW->pCsr;
    Level *pLvl = pMW->pLevel;
    SegmentPtr *aNew1;
    Segment *aNew2;

    Level *pIter;
    Level *pNext;
    int i = 0;

    aNew1 = (SegmentPtr *)lsmMallocZeroRc(
        pDb->pEnv, sizeof(SegmentPtr) * (pCsr->nPtr+nFree), &rc
    );
    if( rc ) return rc;
    memcpy(&aNew1[nFree], pCsr->aPtr, sizeof(SegmentPtr)*pCsr->nPtr);
    pCsr->nPtr += nFree;
    lsmFree(pDb->pEnv, pCsr->aTree);
    lsmFree(pDb->pEnv, pCsr->aPtr);
    pCsr->aTree = 0;
    pCsr->aPtr = aNew1;

    aNew2 = (Segment *)lsmMallocZeroRc(
        pDb->pEnv, sizeof(Segment) * (pLvl->nRight+nFree), &rc
    );
    if( rc ) return rc;
    memcpy(&aNew2[nFree], pLvl->aRhs, sizeof(Segment)*pLvl->nRight);
    pLvl->nRight += nFree;
    lsmFree(pDb->pEnv, pLvl->aRhs);
    pLvl->aRhs = aNew2;

    for(pIter=pDb->pWorker->pLevel; rc==LSM_OK && pIter!=pLvl; pIter=pNext){
      Segment *pSeg = &pLvl->aRhs[i];
      memcpy(pSeg, &pIter->lhs, sizeof(Segment));

      pCsr->aPtr[i].pSeg = pSeg;
      pCsr->aPtr[i].pLevel = pLvl;
      rc = segmentPtrEnd(pCsr, &pCsr->aPtr[i], 0);

      pDb->pWorker->pLevel = pNext = pIter->pNext;
      sortedFreeLevel(pDb->pEnv, pIter);
      i++;
    }
    assert( i==nFree );
    assert( rc!=LSM_OK || pDb->pWorker->pLevel==pLvl );

    for(i=nFree; i<pCsr->nPtr; i++){
      pCsr->aPtr[i].pSeg = &pLvl->aRhs[i];
    }

    lsmFree(pDb->pEnv, pMW->aGobble);
    pMW->aGobble = 0;
  }
  return rc;
}

static int sortedWork(
  lsm_db *pDb,                    /* Database handle. Must be worker. */
  int nWork,                      /* Number of pages of work to do */
  int nMerge,                     /* Try to merge this many levels at once */
  int bFlush,                     /* Set if call is to make room for a flush */
  int *pnWrite                    /* OUT: Actual number of pages written */
................................................................................
    Level *pLevel = 0;

    /* Find a level to work on. */
    rc = sortedSelectLevel(pDb, nMerge, &pLevel);
    assert( rc==LSM_OK || pLevel==0 );

    if( pLevel==0 ){
      int nDone = 0;
      Level *pTopLevel = lsmDbSnapshotLevel(pDb->pWorker);
      if( bFlush==0 && nMerge==1 && pTopLevel && pTopLevel->pNext==0 ){
        rc = sortedMoveBlock(pDb, &nDone);
      }
      nRemaining -= nDone;

      /* Could not find any work to do. Finished. */
      if( nDone==0 ) break;
    }else{
      int bSave = 0;
      Freelist freelist = {0, 0, 0};
      MergeWorker mergeworker;    /* State used to work on the level merge */

      assert( pDb->bIncrMerge==0 );
      assert( pDb->pFreelist==0 && pDb->bUseFreelist==0 );

      pDb->bIncrMerge = 1;
      rc = mergeWorkerInit(pDb, pLevel, &mergeworker);
      assert( mergeworker.nWork==0 );
      
      while( rc==LSM_OK 
          && 0==mergeWorkerDone(&mergeworker) 
          && (mergeworker.nWork<nRemaining || pDb->bUseFreelist)
      ){
        int eType = rtTopic(mergeworker.pCsr->eType);
        rc = mergeWorkerStep(&mergeworker);

        /* If the cursor now points at the first entry past the end of the
        ** user data (i.e. either to EOF or to the first free-list entry
        ** that will be added to the run), then check if it is possible to
        ** merge in any free-list entries that are either in-memory or in
        ** free-list-only blocks.  */
        if( rc==LSM_OK && nMerge==1 && eType==0
         && (rtTopic(mergeworker.pCsr->eType) || mergeWorkerDone(&mergeworker))
        ){
          int nFree = 0;          /* Number of free-list-only levels to merge */
          Level *pLvl;
          assert( pDb->pFreelist==0 && pDb->bUseFreelist==0 );

          /* Now check if all levels containing data newer than this one
          ** are single-segment free-list only levels. If so, they will be
          ** merged in now.  */
          for(pLvl=pDb->pWorker->pLevel; 
              pLvl!=mergeworker.pLevel && (pLvl->flags & LEVEL_FREELIST_ONLY); 
              pLvl=pLvl->pNext
          ){
            assert( pLvl->nRight==0 );
            nFree++;
          }
          if( pLvl==mergeworker.pLevel ){

            rc = mergeInsertFreelistSegments(pDb, nFree, &mergeworker);
            if( rc==LSM_OK ){
              rc = multiCursorVisitFreelist(mergeworker.pCsr);
            }
            if( rc==LSM_OK ){
              rc = multiCursorSetupTree(mergeworker.pCsr, 0);
              pDb->pFreelist = &freelist;
              pDb->bUseFreelist = 1;
            }
          }
        }
      }
      nRemaining -= LSM_MAX(mergeworker.nWork, 1);

      if( rc==LSM_OK ){
        /* Check if the merge operation is completely finished. If not,


        ** gobble up (declare eligible for recycling) any pages from rhs
        ** segments for which the content has been completely merged into 
        ** the lhs of the level.  */


        if( mergeWorkerDone(&mergeworker)==0 ){
          int i;
          for(i=0; i<pLevel->nRight; i++){
            SegmentPtr *pGobble = &mergeworker.pCsr->aPtr[i];
            if( pGobble->pSeg->iRoot ){
              rc = sortedBtreeGobble(pDb, mergeworker.pCsr, i);
            }else if( mergeworker.aGobble[i] ){
              lsmFsGobble(pDb, pGobble->pSeg, &mergeworker.aGobble[i], 1);
            }
          }
        }else{
          int i;
          int bEmpty;
          mergeWorkerShutdown(&mergeworker, &rc);
          bEmpty = (pLevel->lhs.iFirst==0);

          if( bEmpty==0 && rc==LSM_OK ){
            rc = lsmFsSortedFinish(pDb->pFS, &pLevel->lhs);
          }

          if( pDb->bUseFreelist ){
            Freelist *p = &pDb->pWorker->freelist;
            lsmFree(pDb->pEnv, p->aEntry);
            memcpy(p, &freelist, sizeof(freelist));
            pDb->bUseFreelist = 0;
            pDb->pFreelist = 0;
            bSave = 1;
          }


          for(i=0; i<pLevel->nRight; i++){
            lsmFsSortedDelete(pDb->pFS, pWorker, 1, &pLevel->aRhs[i]);
          }

          if( bEmpty ){
            /* If the new level is completely empty, remove it from the 
            ** database snapshot. This can only happen if all input keys were
            ** annihilated. Since keys are only annihilated if the new level
            ** is the last in the linked list (contains the most ancient of
            ** database content), this guarantees that pLevel->pNext==0.  */ 
            Level *pTop;          /* Top level of worker snapshot */
            Level **pp;           /* Read/write iterator for Level.pNext list */

            assert( pLevel->pNext==0 );

            /* Remove the level from the worker snapshot. */
            pTop = lsmDbSnapshotLevel(pWorker);
            for(pp=&pTop; *pp!=pLevel; pp=&((*pp)->pNext));
            *pp = pLevel->pNext;
            lsmDbSnapshotSetLevel(pWorker, pTop);

            /* Free the Level structure. */
            sortedFreeLevel(pDb->pEnv, pLevel);
          }else{


            /* Free the separators of the next level, if required. */
            if( pLevel->pMerge->nInput > pLevel->nRight ){
              assert( pLevel->pNext->lhs.iRoot );
              pLevel->pNext->lhs.iRoot = 0;
            }

            /* Zero the right-hand-side of pLevel */



            lsmFree(pDb->pEnv, pLevel->aRhs);
            pLevel->nRight = 0;
            pLevel->aRhs = 0;

            /* Free the Merge object */
            lsmFree(pDb->pEnv, pLevel->pMerge);
            pLevel->pMerge = 0;
          }

          if( bSave && rc==LSM_OK ){
            pDb->bIncrMerge = 0;
            rc = lsmSaveWorker(pDb, 0);
          }
        }
      }

      /* Clean up the MergeWorker object initialized above. If no error
      ** has occurred, invoke the work-hook to inform the application that
      ** the database structure has changed. */
      mergeWorkerShutdown(&mergeworker, &rc);
      pDb->bIncrMerge = 0;
      if( rc==LSM_OK ) sortedInvokeWorkHook(pDb);


#if LSM_LOG_STRUCTURE
      lsmSortedDumpStructure(pDb, pDb->pWorker, LSM_LOG_DATA, 0, "work");
#endif
      assertBtreeOk(pDb, &pLevel->lhs);
      assertRunInOrder(pDb, &pLevel->lhs);

      /* If bFlush is true and the database is no longer considered "full",
      ** break out of the loop even if nRemaining is still greater than
      ** zero. The caller has an in-memory tree to flush to disk.  */
................................................................................
      bRet = 0;
    }
    *pRc = rc;
  }
  assert( *pRc==LSM_OK || bRet==0 );
  return bRet;
}

/*
** Create a new free-list only top-level segment. Return LSM_OK if successful
** or an LSM error code if some error occurs.
*/
static int sortedNewFreelistOnly(lsm_db *pDb){
  return sortedNewToplevel(pDb, TREE_NONE, 0);
}

int lsmSaveWorker(lsm_db *pDb, int bFlush){
  Snapshot *p = pDb->pWorker;
  if( p->freelist.nEntry>pDb->nMaxFreelist ){
    int rc = sortedNewFreelistOnly(pDb);
    if( rc!=LSM_OK ) return rc;
  }
  return lsmCheckpointSaveWorker(pDb, bFlush);
}

static int doLsmSingleWork(
  lsm_db *pDb, 
  int bShutdown,
  int nMerge,                     /* Minimum segments to merge together */
  int nPage,                      /* Number of pages to write to disk */
  int *pnWrite,                   /* OUT: Pages actually written to disk */
  int *pbCkpt                     /* OUT: True if an auto-checkpoint is req. */
){
  Snapshot *pWorker;              /* Worker snapshot */
  int rc = LSM_OK;                /* Return code */
  int bDirty = 0;
  int nMax = nPage;               /* Maximum pages to write to disk */
  int nRem = nPage;
  int bCkpt = 0;

  assert( nPage>0 );

  /* Open the worker 'transaction'. It will be closed before this function
  ** returns.  */
  assert( pDb->pWorker==0 );
  rc = lsmBeginWork(pDb);
  if( rc!=LSM_OK ) return rc;
  pWorker = pDb->pWorker;

  /* If this connection is doing auto-checkpoints, set nMax (and nRem) so
  ** that this call stops writing when the auto-checkpoint is due. The
  ** caller will do the checkpoint, then possibly call this function again. */
  if( bShutdown==0 && pDb->nAutockpt ){
    u32 nSync;
    u32 nUnsync;
................................................................................
  if( rc==LSM_OK && pDb->pWorker->freelist.nEntry > pDb->nMaxFreelist ){
    int nPg = 0;
    while( rc==LSM_OK && lsmDatabaseFull(pDb) ){
      rc = sortedWork(pDb, 16, nMerge, 1, &nPg);
      nRem -= nPg;
    }
    if( rc==LSM_OK ){
      rc = sortedNewFreelistOnly(pDb);
    }
    nRem -= nPg;
    if( nPg ) bDirty = 1;
  }

  if( rc==LSM_OK ){
    *pnWrite = (nMax - nRem);
    *pbCkpt = (bCkpt && nRem<=0);
    if( nMerge==1 && pDb->nAutockpt>0 && *pnWrite>0
     && pWorker->pLevel 
     && pWorker->pLevel->nRight==0 
     && pWorker->pLevel->pNext==0 
    ){
      *pbCkpt = 1;
    }
  }

  if( rc==LSM_OK && bDirty ){
    lsmFinishWork(pDb, 0, &rc);
  }else{
    int rcdummy = LSM_BUSY;
    lsmFinishWork(pDb, 0, &rcdummy);







    *pnWrite = 0;

  }

  assert( pDb->pWorker==0 );
  return rc;
}

static int doLsmWork(lsm_db *pDb, int nMerge, int nPage, int *pnWrite){
  int rc = LSM_OK;                /* Return code */
  int nWrite = 0;                 /* Number of pages written */


  assert( nMerge>=1 );

  if( nPage>0 ){
    int bCkpt = 0;
    do {
      int nThis = 0;
      bCkpt = 0;
      rc = doLsmSingleWork(pDb, 0, nMerge, nPage-nWrite, &nThis, &bCkpt);
      nWrite += nThis;
      if( rc==LSM_OK && bCkpt ){
        rc = lsm_checkpoint(pDb, 0);
      }
    }while( rc==LSM_OK && (nWrite<nPage && bCkpt) );
  }

  if( pnWrite ){
    if( rc==LSM_OK ){
      *pnWrite = nWrite;
    }else{
      *pnWrite = 0;
    }
................................................................................
    eType = *aCell++;
    assert( (flags & SEGMENT_BTREE_FLAG) || eType!=0 );
    aCell += lsmVarintGet32(aCell, &iPgPtr);

    if( eType==0 ){
      Pgno iRef;                  /* Page number of referenced page */
      aCell += lsmVarintGet64(aCell, &iRef);
      lsmFsDbPageGet(pDb->pFS, pRun, iRef, &pRef);
      aKey = pageGetKey(pRun, pRef, 0, &iTopic, &nKey, &blob);
    }else{
      aCell += lsmVarintGet32(aCell, &nKey);
      if( rtIsWrite(eType) ) aCell += lsmVarintGet32(aCell, &nVal);
      sortedReadData(0, pPg, (aCell-aData), nKey+nVal, (void **)&aKey, &blob);
      aVal = &aKey[nKey];
      iTopic = eType;
    }

    lsmStringAppendf(&s, "%s%2X:", (i==0?"":" "), iTopic);
    for(iChar=0; iChar<nKey; iChar++){
      lsmStringAppendf(&s, "%c", isalnum(aKey[iChar]) ? aKey[iChar] : '.');
................................................................................
  lsmLogMessage(pDb, LSM_OK, "      Page %d: %s", lsmFsPageNumber(pPg), s.z);
  lsmStringClear(&s);

  sortedBlobFree(&blob);
}

static void infoCellDump(
  lsm_db *pDb,                    /* Database handle */
  Segment *pSeg,                  /* Segment page belongs to */
  int bIndirect,                  /* True to follow indirect refs */
  Page *pPg,
  int iCell,
  int *peType,
  int *piPgPtr,
  u8 **paKey, int *pnKey,
  u8 **paVal, int *pnVal,
................................................................................
  aCell += lsmVarintGet32(aCell, &iPgPtr);

  if( eType==0 ){
    int dummy;
    Pgno iRef;                  /* Page number of referenced page */
    aCell += lsmVarintGet64(aCell, &iRef);
    if( bIndirect ){
      lsmFsDbPageGet(pDb->pFS, pSeg, iRef, &pRef);
      pageGetKeyCopy(pDb->pEnv, pSeg, pRef, 0, &dummy, pBlob);
      aKey = (u8 *)pBlob->pData;
      nKey = pBlob->nData;
      lsmFsPageRelease(pRef);
    }else{
      aKey = (u8 *)"<indirect>";
      nKey = 11;
    }
  }else{
    aCell += lsmVarintGet32(aCell, &nKey);
    if( rtIsWrite(eType) ) aCell += lsmVarintGet32(aCell, &nVal);
    sortedReadData(pSeg, pPg, (aCell-aData), nKey+nVal, (void **)&aKey, pBlob);
    aVal = &aKey[nKey];
  }

  if( peType ) *peType = eType;
  if( piPgPtr ) *piPgPtr = iPgPtr;
  if( paKey ) *paKey = aKey;
  if( paVal ) *paVal = aVal;
................................................................................
  int flags,
  char **pzOut                    /* OUT: lsmMalloc'd string */
){
  int rc = LSM_OK;                /* Return code */
  Page *pPg = 0;                  /* Handle for page iPg */
  int i, j;                       /* Loop counters */
  const int perLine = 16;         /* Bytes per line in the raw hex dump */
  Segment *pSeg = 0;
  Snapshot *pSnap;

  int bValues = (flags & INFO_PAGE_DUMP_VALUES);
  int bHex = (flags & INFO_PAGE_DUMP_HEX);
  int bData = (flags & INFO_PAGE_DUMP_DATA);
  int bIndirect = (flags & INFO_PAGE_DUMP_INDIRECT);

  *pzOut = 0;
  if( iPg==0 ) return LSM_ERROR;

  assert( pDb->pClient || pDb->pWorker );
  pSnap = pDb->pClient;
  if( pSnap==0 ) pSnap = pDb->pWorker;
  if( pSnap->redirect.n>0 ){
    Level *pLvl;
    int bUse = 0;
    for(pLvl=pSnap->pLevel; pLvl->pNext; pLvl=pLvl->pNext);
    pSeg = (pLvl->nRight==0 ? &pLvl->lhs : &pLvl->aRhs[pLvl->nRight-1]);
    rc = lsmFsSegmentContainsPg(pDb->pFS, pSeg, iPg, &bUse);
    if( bUse==0 ){
      pSeg = 0;
    }
  }

  /* iPg is a real page number (not subject to redirection). So it is safe 
  ** to pass a NULL in place of the segment pointer as the second argument
  ** to lsmFsDbPageGet() here.  */
  if( rc==LSM_OK ){
    rc = lsmFsDbPageGet(pDb->pFS, 0, iPg, &pPg);
  }

  if( rc==LSM_OK ){
    Blob blob = {0, 0, 0, 0};
    int nKeyWidth = 0;
    LsmString str;
    int nRec;
    int iPtr;
    int flags;
................................................................................
    lsmStringAppendf(&str, "nRec : %d\n", nRec);
    lsmStringAppendf(&str, "iPtr : %d\n", iPtr);
    lsmStringAppendf(&str, "flags: %04x\n", flags);
    lsmStringAppendf(&str, "\n");

    for(iCell=0; iCell<nRec; iCell++){
      int nKey;
      infoCellDump(
          pDb, pSeg, bIndirect, pPg, iCell, 0, 0, 0, &nKey, 0, 0, &blob
      );
      if( nKey>nKeyWidth ) nKeyWidth = nKey;
    }
    if( bHex ) nKeyWidth = nKeyWidth * 2;

    for(iCell=0; iCell<nRec; iCell++){
      u8 *aKey; int nKey = 0;       /* Key */
      u8 *aVal; int nVal = 0;       /* Value */
      int iPgPtr;
      int eType;

      Pgno iAbsPtr;
      char zFlags[8];

      infoCellDump(pDb, pSeg, bIndirect, pPg, iCell, &eType, &iPgPtr,
          &aKey, &nKey, &aVal, &nVal, &blob
      );
      iAbsPtr = iPgPtr + ((flags & SEGMENT_BTREE_FLAG) ? 0 : iPtr);

      lsmFlagsToString(eType, zFlags);
      lsmStringAppendf(&str, "%s %d (%s) ", 
          zFlags, iAbsPtr, (rtTopic(eType) ? "sys" : "usr")
................................................................................
    char *zSeg;
    Page *pPg;

    zSeg = segToString(pDb->pEnv, pRun, 0);
    lsmLogMessage(pDb, LSM_OK, "Segment: %s", zSeg);
    lsmFree(pDb->pEnv, zSeg);

    lsmFsDbPageGet(pDb->pFS, pRun, pRun->iFirst, &pPg);
    while( pPg ){
      Page *pNext;
      char *z = 0;
      infoPageDump(pDb, lsmFsPageNumber(pPg), flags, &z);
      lsmLogMessage(pDb, LSM_OK, "%s", z);
      lsmFree(pDb->pEnv, z);
#if 0
................................................................................
  Snapshot *pSnap,                /* Snapshot to dump */
  int bKeys,                      /* Output the keys from each segment */
  int bVals,                      /* Output the values from each segment */
  const char *zWhy                /* Caption to print near top of dump */
){
  Snapshot *pDump = pSnap;
  Level *pTopLevel;
  char *zFree = 0;


  assert( pSnap );
  pTopLevel = lsmDbSnapshotLevel(pDump);
  if( pDb->xLog && pTopLevel ){
    static int nCall = 0;
    Level *pLevel;
    int iLevel = 0;

    nCall++;
    lsmLogMessage(pDb, LSM_OK, "Database structure %d (%s)", nCall, zWhy);

#if 0
    if( nCall==1031 || nCall==1032 ) bKeys=1;
#endif

    for(pLevel=pTopLevel; pLevel; pLevel=pLevel->pNext){
      char zLeft[1024];
      char zRight[1024];
      int i = 0;

      Segment *aLeft[24];  
................................................................................
        sortedDumpSegment(pDb, &pLevel->lhs, bVals);
        for(i=0; i<pLevel->nRight; i++){
          sortedDumpSegment(pDb, &pLevel->aRhs[i], bVals);
        }
      }
    }
  }

  lsmInfoFreelist(pDb, &zFree);
  lsmLogMessage(pDb, LSM_OK, "Freelist: %s", zFree);
  lsmFree(pDb->pEnv, zFree);

  assert( lsmFsIntegrityCheck(pDb) );
}

void lsmSortedFreeLevel(lsm_env *pEnv, Level *pLevel){
  Level *pNext;
  Level *p;

  for(p=pLevel; p; p=pNext){
................................................................................

#ifdef LSM_DEBUG_EXPENSIVE
static void assertRunInOrder(lsm_db *pDb, Segment *pSeg){
  Page *pPg = 0;
  Blob blob1 = {0, 0, 0, 0};
  Blob blob2 = {0, 0, 0, 0};

  lsmFsDbPageGet(pDb->pFS, pSeg, pSeg->iFirst, &pPg);
  while( pPg ){
    u8 *aData; int nData;
    Page *pNext;

    aData = lsmFsPageData(pPg, &nData);
    if( 0==(pageGetFlags(aData, nData) & SEGMENT_BTREE_FLAG) ){
      int i;
      int nRec = pageGetNRec(aData, nData);
      for(i=0; i<nRec; i++){
        int iTopic1, iTopic2;
        pageGetKeyCopy(pDb->pEnv, pSeg, pPg, i, &iTopic1, &blob1);

        if( i==0 && blob2.nData ){
          assert( sortedKeyCompare(
                pDb->xCmp, iTopic2, blob2.pData, blob2.nData,
                iTopic1, blob1.pData, blob1.nData
          )<0 );
        }

        if( i<(nRec-1) ){
          pageGetKeyCopy(pDb->pEnv, pSeg, pPg, i+1, &iTopic2, &blob2);
          assert( sortedKeyCompare(
                pDb->xCmp, iTopic1, blob1.pData, blob1.nData,
                iTopic2, blob2.pData, blob2.nData
          )<0 );
        }
      }
    }
................................................................................
    BtreeCursor *pCsr = 0;        /* Btree cursor */

    rc = btreeCursorNew(pDb, pSeg, &pCsr);
    if( rc==LSM_OK ){
      rc = btreeCursorFirst(pCsr);
    }
    if( rc==LSM_OK ){
      rc = lsmFsDbPageGet(pFS, pSeg, pSeg->iFirst, &pPg);
    }

    while( rc==LSM_OK ){
      Page *pNext;
      u8 *aData;
      int nData;
      int flags;
................................................................................
      if( rc==LSM_OK 
       && 0==((SEGMENT_BTREE_FLAG|PGFTR_SKIP_THIS_FLAG) & flags)
       && 0!=pageGetNRec(aData, nData)
      ){
        u8 *pKey;
        int nKey;
        int iTopic;
        pKey = pageGetKey(pSeg, pPg, 0, &iTopic, &nKey, &blob);
        assert( nKey==pCsr->nKey && 0==memcmp(pKey, pCsr->pKey, nKey) );
        assert( lsmFsPageNumber(pPg)==pCsr->iPtr );
        rc = btreeCursorNext(pCsr);
      }
    }
    assert( rc!=LSM_OK || pCsr->pKey==0 );

Changes to tool/lsmview.tcl.

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  }
  namespace export scrollable
}
namespace import ::autoscroll::*
#############################################################################

proc exec_lsmtest_show {args} {
  set fd [open [list |lsmtest show {*}$args]]
  set res ""
  while {![eof $fd]} { 
    set line [gets $fd]
    if {[regexp {^\#.*} $line]} continue
    if {[regexp {^Leaked*} $line]} continue
    append res $line
    append res "\n"







|







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  }
  namespace export scrollable
}
namespace import ::autoscroll::*
#############################################################################

proc exec_lsmtest_show {args} {
  set fd [open [list |lsmtest show {*}$args 2>/dev/null]]
  set res ""
  while {![eof $fd]} { 
    set line [gets $fd]
    if {[regexp {^\#.*} $line]} continue
    if {[regexp {^Leaked*} $line]} continue
    append res $line
    append res "\n"