char *zLanguageid;              /* languageid=xxx option, or NULL */
  u8 bAutoincrmerge;              /* True if automerge=1 */
  u32 nLeafAdd;                   /* Number of leaf blocks added this trans */

  /* Precompiled statements used by the implementation. Each of these 
  ** statements is run and reset within a single virtual table API call. 
  */
  sqlite3_stmt *aStmt[37];

  char *zReadExprlist;
  char *zWriteExprlist;

  int nNodeSize;                  /* Soft limit for node size */
  u8 bFts4;                       /* True for FTS4, false for FTS3 */
  u8 bHasStat;                    /* True if %_stat table exists (2==unknown) */

  char *zLanguageid;              /* languageid=xxx option, or NULL */
  u8 bAutoincrmerge;              /* True if automerge=1 */
  u32 nLeafAdd;                   /* Number of leaf blocks added this trans */

  /* Precompiled statements used by the implementation. Each of these 
  ** statements is run and reset within a single virtual table API call. 
  */
  sqlite3_stmt *aStmt[40];

  char *zReadExprlist;
  char *zWriteExprlist;

  int nNodeSize;                  /* Soft limit for node size */
  u8 bFts4;                       /* True for FTS4, false for FTS3 */
  u8 bHasStat;                    /* True if %_stat table exists (2==unknown) */

  char *zTerm;                    /* Pointer to previous term buffer */
  int nTerm;                      /* Number of bytes in zTerm */
  int nMalloc;                    /* Size of malloc'd buffer at zMalloc */
  char *zMalloc;                  /* Malloc'd space (possibly) used for zTerm */
  int nSize;                      /* Size of allocation at aData */
  int nData;                      /* Bytes of data in aData */
  char *aData;                    /* Pointer to block from malloc() */

};

/*
** Type SegmentNode is used by the following three functions to create
** the interior part of the segment b+-tree structures (everything except
** the leaf nodes). These functions and type are only ever used by code
** within the fts3SegWriterXXX() family of functions described above.
................................................................................
#define SQL_DELETE_SEGDIR_ENTRY       30
#define SQL_SHIFT_SEGDIR_ENTRY        31
#define SQL_SELECT_SEGDIR             32
#define SQL_CHOMP_SEGDIR              33
#define SQL_SEGMENT_IS_APPENDABLE     34
#define SQL_SELECT_INDEXES            35
#define SQL_SELECT_MXLEVEL            36





/*
** This function is used to obtain an SQLite prepared statement handle
** for the statement identified by the second argument. If successful,
** *pp is set to the requested statement handle and SQLITE_OK returned.
** Otherwise, an SQLite error code is returned and *pp is set to 0.
**
................................................................................

/* SQL_SELECT_INDEXES
**   Return the list of valid segment indexes for absolute level ?  */
/* 35 */  "SELECT idx FROM %Q.'%q_segdir' WHERE level=? ORDER BY 1 ASC",

/* SQL_SELECT_MXLEVEL
**   Return the largest relative level in the FTS index or indexes.  */
/* 36 */  "SELECT max( level %% 1024 ) FROM %Q.'%q_segdir'"










  };
  int rc = SQLITE_OK;
  sqlite3_stmt *pStmt;

  assert( SizeofArray(azSql)==SizeofArray(p->aStmt) );
  assert( eStmt<SizeofArray(azSql) && eStmt>=0 );
  
................................................................................
static int fts3WriteSegdir(
  Fts3Table *p,                   /* Virtual table handle */
  sqlite3_int64 iLevel,           /* Value for "level" field (absolute level) */
  int iIdx,                       /* Value for "idx" field */
  sqlite3_int64 iStartBlock,      /* Value for "start_block" field */
  sqlite3_int64 iLeafEndBlock,    /* Value for "leaves_end_block" field */
  sqlite3_int64 iEndBlock,        /* Value for "end_block" field */

  char *zRoot,                    /* Blob value for "root" field */
  int nRoot                       /* Number of bytes in buffer zRoot */
){
  sqlite3_stmt *pStmt;
  int rc = fts3SqlStmt(p, SQL_INSERT_SEGDIR, &pStmt, 0);
  if( rc==SQLITE_OK ){
    sqlite3_bind_int64(pStmt, 1, iLevel);
    sqlite3_bind_int(pStmt, 2, iIdx);
    sqlite3_bind_int64(pStmt, 3, iStartBlock);
    sqlite3_bind_int64(pStmt, 4, iLeafEndBlock);

    sqlite3_bind_int64(pStmt, 5, iEndBlock);





    sqlite3_bind_blob(pStmt, 6, zRoot, nRoot, SQLITE_STATIC);
    sqlite3_step(pStmt);
    rc = sqlite3_reset(pStmt);
  }
  return rc;
}

................................................................................
    nSuffix = nTerm;
    nReq = 1 +                              /* varint containing prefix size */
      sqlite3Fts3VarintLen(nTerm) +         /* varint containing suffix size */
      nTerm +                               /* Term suffix */
      sqlite3Fts3VarintLen(nDoclist) +      /* Size of doclist */
      nDoclist;                             /* Doclist data */
  }




  /* If the buffer currently allocated is too small for this entry, realloc
  ** the buffer to make it large enough.
  */
  if( nReq>pWriter->nSize ){
    char *aNew = sqlite3_realloc(pWriter->aData, nReq);
    if( !aNew ) return SQLITE_NOMEM;
................................................................................
    iLastLeaf = pWriter->iFree;
    rc = fts3WriteSegment(p, pWriter->iFree++, pWriter->aData, pWriter->nData);
    if( rc==SQLITE_OK ){
      rc = fts3NodeWrite(p, pWriter->pTree, 1,
          pWriter->iFirst, pWriter->iFree, &iLast, &zRoot, &nRoot);
    }
    if( rc==SQLITE_OK ){
      rc = fts3WriteSegdir(
          p, iLevel, iIdx, pWriter->iFirst, iLastLeaf, iLast, zRoot, nRoot);
    }
  }else{
    /* The entire tree fits on the root node. Write it to the segdir table. */
    rc = fts3WriteSegdir(
        p, iLevel, iIdx, 0, 0, 0, pWriter->aData, pWriter->nData);
  }
  p->nLeafAdd++;
  return rc;
}

/*
** Release all memory held by the SegmentWriter object passed as the 
................................................................................
    sqlite3_free(pCsr->aBuffer);

    pCsr->nSegment = 0;
    pCsr->apSegment = 0;
    pCsr->aBuffer = 0;
  }
}





































































































/*
** Merge all level iLevel segments in the database into a single 
** iLevel+1 segment. Or, if iLevel<0, merge all segments into a
** single segment with a level equal to the numerically largest level 
** currently present in the database.
**
................................................................................
  if( iLevel!=FTS3_SEGCURSOR_PENDING ){
    rc = fts3DeleteSegdir(
        p, iLangid, iIndex, iLevel, csr.apSegment, csr.nSegment
    );
    if( rc!=SQLITE_OK ) goto finished;
  }
  rc = fts3SegWriterFlush(p, pWriter, iNewLevel, iIdx);




 finished:
  fts3SegWriterFree(pWriter);
  sqlite3Fts3SegReaderFinish(&csr);
  return rc;
}


/* 
** Flush the contents of pendingTerms to level 0 segments.
*/
int sqlite3Fts3PendingTermsFlush(Fts3Table *p){
  int rc = SQLITE_OK;
  int i;
        
  for(i=0; rc==SQLITE_OK && i<p->nIndex; i++){
    rc = fts3SegmentMerge(p, p->iPrevLangid, i, FTS3_SEGCURSOR_PENDING);
................................................................................
struct IncrmergeWriter {
  int nLeafEst;                   /* Space allocated for leaf blocks */
  int nWork;                      /* Number of leaf pages flushed */
  sqlite3_int64 iAbsLevel;        /* Absolute level of input segments */
  int iIdx;                       /* Index of *output* segment in iAbsLevel+1 */
  sqlite3_int64 iStart;           /* Block number of first allocated block */
  sqlite3_int64 iEnd;             /* Block number of last allocated block */

  NodeWriter aNodeWriter[FTS_MAX_APPENDABLE_HEIGHT];
};

/*
** An object of the following type is used to read data from a single
** FTS segment node. See the following functions:
**
................................................................................

    nSuffix = nTerm;
    nSpace  = 1;
    nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
    nSpace += sqlite3Fts3VarintLen(nDoclist) + nDoclist;
  }


  blobGrowBuffer(&pLeaf->block, pLeaf->block.n + nSpace, &rc);

  if( rc==SQLITE_OK ){
    if( pLeaf->block.n==0 ){
      pLeaf->block.n = 1;
      pLeaf->block.a[0] = '\0';
    }
    rc = fts3AppendToNode(
        &pLeaf->block, &pLeaf->key, zTerm, nTerm, aDoclist, nDoclist
................................................................................
  if( rc==SQLITE_OK ){
    rc = fts3WriteSegdir(p, 
        pWriter->iAbsLevel+1,               /* level */
        pWriter->iIdx,                      /* idx */
        pWriter->iStart,                    /* start_block */
        pWriter->aNodeWriter[0].iBlock,     /* leaves_end_block */
        pWriter->iEnd,                      /* end_block */

        pRoot->block.a, pRoot->block.n      /* root */
    );
  }
  sqlite3_free(pRoot->block.a);
  sqlite3_free(pRoot->key.a);

  *pRc = rc;
................................................................................

    /* Read the %_segdir entry for index iIdx absolute level (iAbsLevel+1) */
    sqlite3_bind_int64(pSelect, 1, iAbsLevel+1);
    sqlite3_bind_int(pSelect, 2, iIdx);
    if( sqlite3_step(pSelect)==SQLITE_ROW ){
      iStart = sqlite3_column_int64(pSelect, 1);
      iLeafEnd = sqlite3_column_int64(pSelect, 2);
      iEnd = sqlite3_column_int64(pSelect, 3);
      nRoot = sqlite3_column_bytes(pSelect, 4);
      aRoot = sqlite3_column_blob(pSelect, 4);
    }else{
      return sqlite3_reset(pSelect);
    }

    /* Check for the zero-length marker in the %_segments table */
................................................................................
  return SQLITE_OK;
}


/*
** Attempt an incremental merge that writes nMerge leaf blocks.
**
** Incremental merges happen nMin segments at a time. The two
** segments to be merged are the nMin oldest segments (the ones with
** the smallest indexes) in the highest level that contains at least
** nMin segments. Multiple merges might occur in an attempt to write the 
** quota of nMerge leaf blocks.
*/
int sqlite3Fts3Incrmerge(Fts3Table *p, int nMerge, int nMin){
  int rc;                         /* Return code */
  int nRem = nMerge;              /* Number of leaf pages yet to  be written */
  Fts3MultiSegReader *pCsr;       /* Cursor used to read input data */
  Fts3SegFilter *pFilter;         /* Filter used with cursor pCsr */
  IncrmergeWriter *pWriter;       /* Writer object */
................................................................................
            bDirtyHint = 1;
            fts3IncrmergeHintPush(&hint, iAbsLevel, nSeg, &rc);
          }
        }
      }

      fts3IncrmergeRelease(p, pWriter, &rc);



    }

    sqlite3Fts3SegReaderFinish(pCsr);
  }

  /* Write the hint values into the %_stat table for the next incr-merger */
  if( bDirtyHint && rc==SQLITE_OK ){

  char *zTerm;                    /* Pointer to previous term buffer */
  int nTerm;                      /* Number of bytes in zTerm */
  int nMalloc;                    /* Size of malloc'd buffer at zMalloc */
  char *zMalloc;                  /* Malloc'd space (possibly) used for zTerm */
  int nSize;                      /* Size of allocation at aData */
  int nData;                      /* Bytes of data in aData */
  char *aData;                    /* Pointer to block from malloc() */
  i64 nLeafData;                  /* Number of bytes of leaf data written */
};

/*
** Type SegmentNode is used by the following three functions to create
** the interior part of the segment b+-tree structures (everything except
** the leaf nodes). These functions and type are only ever used by code
** within the fts3SegWriterXXX() family of functions described above.
................................................................................
#define SQL_DELETE_SEGDIR_ENTRY       30
#define SQL_SHIFT_SEGDIR_ENTRY        31
#define SQL_SELECT_SEGDIR             32
#define SQL_CHOMP_SEGDIR              33
#define SQL_SEGMENT_IS_APPENDABLE     34
#define SQL_SELECT_INDEXES            35
#define SQL_SELECT_MXLEVEL            36

#define SQL_SELECT_LEVEL_RANGE2       37
#define SQL_UPDATE_LEVEL_IDX          38
#define SQL_UPDATE_LEVEL              39

/*
** This function is used to obtain an SQLite prepared statement handle
** for the statement identified by the second argument. If successful,
** *pp is set to the requested statement handle and SQLITE_OK returned.
** Otherwise, an SQLite error code is returned and *pp is set to 0.
**
................................................................................

/* SQL_SELECT_INDEXES
**   Return the list of valid segment indexes for absolute level ?  */
/* 35 */  "SELECT idx FROM %Q.'%q_segdir' WHERE level=? ORDER BY 1 ASC",

/* SQL_SELECT_MXLEVEL
**   Return the largest relative level in the FTS index or indexes.  */
/* 36 */  "SELECT max( level %% 1024 ) FROM %Q.'%q_segdir'",

          /* Return segments in order from oldest to newest.*/ 
/* 37 */  "SELECT level, idx, end_block "
            "FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?"
            "ORDER BY level DESC, idx ASC",

          /* Update statements used while promoting segments */
/* 38 */  "UPDATE %Q.'%q_segdir' SET level=-1,idx=? WHERE level=? AND idx=?",
/* 39 */  "UPDATE %Q.'%q_segdir' SET level=? WHERE level=-1"

  };
  int rc = SQLITE_OK;
  sqlite3_stmt *pStmt;

  assert( SizeofArray(azSql)==SizeofArray(p->aStmt) );
  assert( eStmt<SizeofArray(azSql) && eStmt>=0 );
  
................................................................................
static int fts3WriteSegdir(
  Fts3Table *p,                   /* Virtual table handle */
  sqlite3_int64 iLevel,           /* Value for "level" field (absolute level) */
  int iIdx,                       /* Value for "idx" field */
  sqlite3_int64 iStartBlock,      /* Value for "start_block" field */
  sqlite3_int64 iLeafEndBlock,    /* Value for "leaves_end_block" field */
  sqlite3_int64 iEndBlock,        /* Value for "end_block" field */
  sqlite3_int64 nLeafData,        /* Bytes of leaf data in segment */
  char *zRoot,                    /* Blob value for "root" field */
  int nRoot                       /* Number of bytes in buffer zRoot */
){
  sqlite3_stmt *pStmt;
  int rc = fts3SqlStmt(p, SQL_INSERT_SEGDIR, &pStmt, 0);
  if( rc==SQLITE_OK ){
    sqlite3_bind_int64(pStmt, 1, iLevel);
    sqlite3_bind_int(pStmt, 2, iIdx);
    sqlite3_bind_int64(pStmt, 3, iStartBlock);
    sqlite3_bind_int64(pStmt, 4, iLeafEndBlock);
    if( nLeafData==0 ){
      sqlite3_bind_int64(pStmt, 5, iEndBlock);
    }else{
      char *zEnd = sqlite3_mprintf("%lld %lld", iEndBlock, nLeafData);
      if( !zEnd ) return SQLITE_NOMEM;
      sqlite3_bind_text(pStmt, 5, zEnd, -1, sqlite3_free);
    }
    sqlite3_bind_blob(pStmt, 6, zRoot, nRoot, SQLITE_STATIC);
    sqlite3_step(pStmt);
    rc = sqlite3_reset(pStmt);
  }
  return rc;
}

................................................................................
    nSuffix = nTerm;
    nReq = 1 +                              /* varint containing prefix size */
      sqlite3Fts3VarintLen(nTerm) +         /* varint containing suffix size */
      nTerm +                               /* Term suffix */
      sqlite3Fts3VarintLen(nDoclist) +      /* Size of doclist */
      nDoclist;                             /* Doclist data */
  }

  /* Increase the total number of bytes written to account for the new entry. */
  pWriter->nLeafData += nReq;

  /* If the buffer currently allocated is too small for this entry, realloc
  ** the buffer to make it large enough.
  */
  if( nReq>pWriter->nSize ){
    char *aNew = sqlite3_realloc(pWriter->aData, nReq);
    if( !aNew ) return SQLITE_NOMEM;
................................................................................
    iLastLeaf = pWriter->iFree;
    rc = fts3WriteSegment(p, pWriter->iFree++, pWriter->aData, pWriter->nData);
    if( rc==SQLITE_OK ){
      rc = fts3NodeWrite(p, pWriter->pTree, 1,
          pWriter->iFirst, pWriter->iFree, &iLast, &zRoot, &nRoot);
    }
    if( rc==SQLITE_OK ){
      rc = fts3WriteSegdir(p, iLevel, iIdx, 
          pWriter->iFirst, iLastLeaf, iLast, pWriter->nLeafData, zRoot, nRoot);
    }
  }else{
    /* The entire tree fits on the root node. Write it to the segdir table. */
    rc = fts3WriteSegdir(p, iLevel, iIdx, 
        0, 0, 0, pWriter->nLeafData, pWriter->aData, pWriter->nData);
  }
  p->nLeafAdd++;
  return rc;
}

/*
** Release all memory held by the SegmentWriter object passed as the 
................................................................................
    sqlite3_free(pCsr->aBuffer);

    pCsr->nSegment = 0;
    pCsr->apSegment = 0;
    pCsr->aBuffer = 0;
  }
}

/*
** Decode the "end_block" field, selected by column iCol of the SELECT 
** statement passed as the first argument. 
*/
static void fts3ReadEndBlockField(
  sqlite3_stmt *pStmt, 
  int iCol, 
  i64 *piEndBlock, 
  i64 *pnByte
){
  const unsigned char *zText = sqlite3_column_text(pStmt, iCol);
  if( zText ){
    int i;
    i64 iVal = 0;
    for(i=0; zText[i]>='0' && zText[i]<='9'; i++){
      iVal = iVal*10 + (zText[i] - '0');
    }
    *piEndBlock = iVal;
    while( zText[i]==' ' ) i++;
    iVal = 0;
    for(/* no-op */; zText[i]>='0' && zText[i]<='9'; i++){
      iVal = iVal*10 + (zText[i] - '0');
    }
    *pnByte = iVal;
  }
}


/*
** A segment of size nByte bytes has just been written to absolute level
** iAbsLevel. Promote any segments that should be promoted as a result.
*/
static int fts3PromoteSegments(
  Fts3Table *p,                   /* FTS table handle */
  int iAbsLevel,                  /* Absolute level just updated */
  sqlite3_int64 nByte             /* Size of new segment at iAbsLevel */
){
  int rc = SQLITE_OK;
  sqlite3_stmt *pRange;

  rc = fts3SqlStmt(p, SQL_SELECT_LEVEL_RANGE2, &pRange, 0);

  if( rc==SQLITE_OK ){
    int bOk = 1;
    int iLast = (iAbsLevel/FTS3_SEGDIR_MAXLEVEL + 1) * FTS3_SEGDIR_MAXLEVEL - 1;

    sqlite3_bind_int(pRange, 1, iAbsLevel+1);
    sqlite3_bind_int(pRange, 2, iLast);
    while( SQLITE_ROW==sqlite3_step(pRange) ){
      i64 nSize, dummy;
      fts3ReadEndBlockField(pRange, 2, &dummy, &nSize);
      if( nSize>nByte ){
        bOk = 0;
        break;
      }
    }
    rc = sqlite3_reset(pRange);

    if( bOk ){
      int iIdx = 0;
      sqlite3_stmt *pUpdate1;
      sqlite3_stmt *pUpdate2;

      if( rc==SQLITE_OK ){
        rc = fts3SqlStmt(p, SQL_UPDATE_LEVEL_IDX, &pUpdate1, 0);
      }
      if( rc==SQLITE_OK ){
        rc = fts3SqlStmt(p, SQL_UPDATE_LEVEL, &pUpdate2, 0);
      }

      if( rc==SQLITE_OK ){
        sqlite3_bind_int(pRange, 1, iAbsLevel);
        while( SQLITE_ROW==sqlite3_step(pRange) ){
          sqlite3_bind_int(pUpdate1, 1, iIdx++);
          sqlite3_bind_int(pUpdate1, 2, sqlite3_column_int(pRange, 0));
          sqlite3_bind_int(pUpdate1, 3, sqlite3_column_int(pRange, 1));
          sqlite3_step(pUpdate1);
          rc = sqlite3_reset(pUpdate1);
          if( rc!=SQLITE_OK ){
            sqlite3_reset(pRange);
            break;
          }
        }
      }
      if( rc==SQLITE_OK ){
        rc = sqlite3_reset(pRange);
      }

      if( rc==SQLITE_OK ){
        sqlite3_bind_int(pUpdate2, 1, iAbsLevel);
        sqlite3_step(pUpdate2);
        rc = sqlite3_reset(pUpdate2);
      }
    }
  }


  return rc;
}

/*
** Merge all level iLevel segments in the database into a single 
** iLevel+1 segment. Or, if iLevel<0, merge all segments into a
** single segment with a level equal to the numerically largest level 
** currently present in the database.
**
................................................................................
  if( iLevel!=FTS3_SEGCURSOR_PENDING ){
    rc = fts3DeleteSegdir(
        p, iLangid, iIndex, iLevel, csr.apSegment, csr.nSegment
    );
    if( rc!=SQLITE_OK ) goto finished;
  }
  rc = fts3SegWriterFlush(p, pWriter, iNewLevel, iIdx);
  if( rc==SQLITE_OK ){
    rc = fts3PromoteSegments(p, iNewLevel, pWriter->nLeafData);
  }

 finished:
  fts3SegWriterFree(pWriter);
  sqlite3Fts3SegReaderFinish(&csr);
  return rc;
}


/* 
** Flush the contents of pendingTerms to level 0 segments. 
*/
int sqlite3Fts3PendingTermsFlush(Fts3Table *p){
  int rc = SQLITE_OK;
  int i;
        
  for(i=0; rc==SQLITE_OK && i<p->nIndex; i++){
    rc = fts3SegmentMerge(p, p->iPrevLangid, i, FTS3_SEGCURSOR_PENDING);
................................................................................
struct IncrmergeWriter {
  int nLeafEst;                   /* Space allocated for leaf blocks */
  int nWork;                      /* Number of leaf pages flushed */
  sqlite3_int64 iAbsLevel;        /* Absolute level of input segments */
  int iIdx;                       /* Index of *output* segment in iAbsLevel+1 */
  sqlite3_int64 iStart;           /* Block number of first allocated block */
  sqlite3_int64 iEnd;             /* Block number of last allocated block */
  sqlite3_int64 nLeafData;        /* Bytes of leaf page data so far */
  NodeWriter aNodeWriter[FTS_MAX_APPENDABLE_HEIGHT];
};

/*
** An object of the following type is used to read data from a single
** FTS segment node. See the following functions:
**
................................................................................

    nSuffix = nTerm;
    nSpace  = 1;
    nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
    nSpace += sqlite3Fts3VarintLen(nDoclist) + nDoclist;
  }

  pWriter->nLeafData += nSpace;
  blobGrowBuffer(&pLeaf->block, pLeaf->block.n + nSpace, &rc);

  if( rc==SQLITE_OK ){
    if( pLeaf->block.n==0 ){
      pLeaf->block.n = 1;
      pLeaf->block.a[0] = '\0';
    }
    rc = fts3AppendToNode(
        &pLeaf->block, &pLeaf->key, zTerm, nTerm, aDoclist, nDoclist
................................................................................
  if( rc==SQLITE_OK ){
    rc = fts3WriteSegdir(p, 
        pWriter->iAbsLevel+1,               /* level */
        pWriter->iIdx,                      /* idx */
        pWriter->iStart,                    /* start_block */
        pWriter->aNodeWriter[0].iBlock,     /* leaves_end_block */
        pWriter->iEnd,                      /* end_block */
        pWriter->nLeafData,                 /* end_block */
        pRoot->block.a, pRoot->block.n      /* root */
    );
  }
  sqlite3_free(pRoot->block.a);
  sqlite3_free(pRoot->key.a);

  *pRc = rc;
................................................................................

    /* Read the %_segdir entry for index iIdx absolute level (iAbsLevel+1) */
    sqlite3_bind_int64(pSelect, 1, iAbsLevel+1);
    sqlite3_bind_int(pSelect, 2, iIdx);
    if( sqlite3_step(pSelect)==SQLITE_ROW ){
      iStart = sqlite3_column_int64(pSelect, 1);
      iLeafEnd = sqlite3_column_int64(pSelect, 2);
      fts3ReadEndBlockField(pSelect, 3, &iEnd, &pWriter->nLeafData);
      nRoot = sqlite3_column_bytes(pSelect, 4);
      aRoot = sqlite3_column_blob(pSelect, 4);
    }else{
      return sqlite3_reset(pSelect);
    }

    /* Check for the zero-length marker in the %_segments table */
................................................................................
  return SQLITE_OK;
}


/*
** Attempt an incremental merge that writes nMerge leaf blocks.
**
** Incremental merges happen nMin segments at a time. The segments 
** to be merged are the nMin oldest segments (the ones with the smallest 
** values for the _segdir.idx field) in the highest level that contains 
** at least nMin segments. Multiple merges might occur in an attempt to 
** write the quota of nMerge leaf blocks.
*/
int sqlite3Fts3Incrmerge(Fts3Table *p, int nMerge, int nMin){
  int rc;                         /* Return code */
  int nRem = nMerge;              /* Number of leaf pages yet to  be written */
  Fts3MultiSegReader *pCsr;       /* Cursor used to read input data */
  Fts3SegFilter *pFilter;         /* Filter used with cursor pCsr */
  IncrmergeWriter *pWriter;       /* Writer object */
................................................................................
            bDirtyHint = 1;
            fts3IncrmergeHintPush(&hint, iAbsLevel, nSeg, &rc);
          }
        }
      }

      fts3IncrmergeRelease(p, pWriter, &rc);
      if( nSeg==0 ){
        fts3PromoteSegments(p, iAbsLevel+1, pWriter->nLeafData);
      }
    }

    sqlite3Fts3SegReaderFinish(pCsr);
  }

  /* Write the hint values into the %_stat table for the next incr-merger */
  if( bDirtyHint && rc==SQLITE_OK ){

# 2014 May 12
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#*************************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is testing the FTS4 module.
#
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix fts4growth

# If SQLITE_ENABLE_FTS3 is defined, omit this file.
ifcapable !fts3 {
  finish_test
  return
}

source $testdir/genesis.tcl

do_execsql_test 1.1 { CREATE VIRTUAL TABLE x1 USING fts3; }

do_test 1.2 {
  foreach L {
    {"See here, young man," said Mulga Bill, "from Walgett to the sea,}
    {From Conroy's Gap to Castlereagh, there's none can ride like me.}
    {I'm good all round at everything as everybody knows,}
    {Although I'm not the one to talk -- I hate a man that blows.}
  } {
    execsql { INSERT INTO x1 VALUES($L) }
  }
  execsql { SELECT end_block, length(root) FROM x1_segdir }
} {{0 114} 114 {0 118} 118 {0 95} 95 {0 115} 115}

do_execsql_test 1.3 {
  INSERT INTO x1(x1) VALUES('optimize');
  SELECT level, end_block, length(root) FROM x1_segdir;
} {0 {0 394} 394}

do_test 1.4 {
  foreach L {
    {But riding is my special gift, my chiefest, sole delight;}
    {Just ask a wild duck can it swim, a wildcat can it fight.}
    {There's nothing clothed in hair or hide, or built of flesh or steel,}
    {There's nothing walks or jumps, or runs, on axle, hoof, or wheel,}
    {But what I'll sit, while hide will hold and girths and straps are tight:}
    {I'll ride this here two-wheeled concern right straight away at sight."}
  } {
    execsql { INSERT INTO x1 VALUES($L) }
  }
  execsql { 
    INSERT INTO x1(x1) VALUES('merge=4,4');
    SELECT level, end_block, length(root) FROM x1_segdir;
  }
} {0 {0 110} 110 0 {0 132} 132 0 {0 129} 129 1 {128 658} 2}

do_execsql_test 1.5 {
  SELECT length(block) FROM x1_segments;
} {658 {}}

do_test 1.6 {
  foreach L {
    {'Twas Mulga Bill, from Eaglehawk, that sought his own abode,}
    {That perched above Dead Man's Creek, beside the mountain road.}
    {He turned the cycle down the hill and mounted for the fray,}
    {But 'ere he'd gone a dozen yards it bolted clean away.}
    {It left the track, and through the trees, just like a silver steak,}
    {It whistled down the awful slope towards the Dead Man's Creek.}
    {It shaved a stump by half an inch, it dodged a big white-box:}
    {The very wallaroos in fright went scrambling up the rocks,}
    {The wombats hiding in their caves dug deeper underground,}
    {As Mulga Bill, as white as chalk, sat tight to every bound.}
    {It struck a stone and gave a spring that cleared a fallen tree,}
    {It raced beside a precipice as close as close could be;}
    {And then as Mulga Bill let out one last despairing shriek}
    {It made a leap of twenty feet into the Dead Man's Creek.}
  } {
    execsql { INSERT INTO x1 VALUES($L) }
  }
  execsql { 
    SELECT level, end_block, length(root) FROM x1_segdir;
  }
} {1 {128 658} 2 1 {130 1377} 6 0 {0 117} 117}

do_execsql_test 1.7 {
  SELECT sum(length(block)) FROM x1_segments WHERE blockid IN (129, 130);
} {1377}

#-------------------------------------------------------------------------
#
do_execsql_test 2.1 { 
  CREATE TABLE t1(docid, words);
  CREATE VIRTUAL TABLE x2 USING fts4;
}
fts_kjv_genesis 
do_test 2.2 {
  foreach id [db eval {SELECT docid FROM t1}] {
    execsql {
      INSERT INTO x2(docid, content) SELECT $id, words FROM t1 WHERE docid=$id
    }
  }
  foreach id [db eval {SELECT docid FROM t1}] {
    execsql {
      INSERT INTO x2(docid, content) SELECT NULL, words FROM t1 WHERE docid=$id
    }
    if {[db one {SELECT count(*) FROM x2_segdir WHERE level<2}]==2} break
  }
} {}

do_execsql_test 2.3 { 
  SELECT count(*) FROM x2_segdir WHERE level=2;
  SELECT count(*) FROM x2_segdir WHERE level=3;
} {6 0}

do_execsql_test 2.4 { 
  INSERT INTO x2(x2) VALUES('merge=4,4');
  SELECT count(*) FROM x2_segdir WHERE level=2;
  SELECT count(*) FROM x2_segdir WHERE level=3;
} {6 1}

do_execsql_test 2.5 { 
  SELECT end_block FROM x2_segdir WHERE level=3;
  INSERT INTO x2(x2) VALUES('merge=4,4');
  SELECT end_block FROM x2_segdir WHERE level=3;
  INSERT INTO x2(x2) VALUES('merge=4,4');
  SELECT end_block FROM x2_segdir WHERE level=3;
} {{3828 3430} {3828 10191} {3828 14109}}

do_execsql_test 2.6 {
  SELECT sum(length(block)) FROM x2_segdir, x2_segments WHERE 
    blockid BETWEEN start_block AND leaves_end_block
    AND level=3
} {14109}

do_execsql_test 2.7 { 
  INSERT INTO x2(x2) VALUES('merge=1000,4');
  SELECT end_block FROM x2_segdir WHERE level=3;
} {{3828 86120}}

do_execsql_test 2.8 {
  SELECT sum(length(block)) FROM x2_segdir, x2_segments WHERE 
    blockid BETWEEN start_block AND leaves_end_block
    AND level=3
} {86120}

#--------------------------------------------------------------------------

do_execsql_test 3.1 {
  DROP TABLE IF EXISTS x2;
  DROP TABLE IF EXISTS t1;
  CREATE TABLE t1(docid, words);
  CREATE VIRTUAL TABLE x2 USING fts4;
}
fts_kjv_genesis 

proc t1_to_x2 {} {
  foreach id [db eval {SELECT docid FROM t1 LIMIT 2}] {
    execsql {
      DELETE FROM x2 WHERE docid=$id;
      INSERT INTO x2(docid, content) SELECT $id, words FROM t1 WHERE docid=$id;
    }
  }
}

#do_test 3.2 {
  #t1_to_x2
  #execsql {SELECT level, count(*) FROM x2_segdir GROUP BY level}
#} {0 13 1 15 2 5}

#proc second {x} { lindex $x 1 }
#db func second second
#for {set i 0} {$i <1000} {incr i} {
#  t1_to_x2
#  db eval {
#    SELECT level, group_concat( second(end_block), ' ' ) AS c FROM x2_segdir GROUP BY level;
#  } {
#    puts "$i.$level: $c"
#  }
#}


finish_test