SQLite

        fts5NodeIterInit(pPg->buf.p, pPg->buf.n, &ss);
        while( ss.aData ) fts5NodeIterNext(&p->rc, &ss);
        fts5BufferSet(&p->rc, &pPg->term, ss.term.n, ss.term.p);
        pgno = ss.iChild;
        fts5NodeIterFree(&ss);
      }
    }



    assert( p->rc!=SQLITE_OK || (pgno+pWriter->nEmpty)==pSeg->pgnoLast );
    pWriter->bFirstTermInPage = 1;
    assert( pWriter->aWriter[0].term.n==0 );
  }
}

/*

  return fts5IndexReturn(p); 
}

int sqlite3Fts5IndexMerge(Fts5Index *p, int nMerge){
  Fts5Structure *pStruct;

  pStruct = fts5StructureRead(p);
  if( pStruct && pStruct->nLevel ){
    fts5IndexMerge(p, &pStruct, nMerge);
    fts5StructureWrite(p, pStruct);
  }
  fts5StructureRelease(pStruct);

  return fts5IndexReturn(p);
}


/*

       || (flags & FTS5INDEX_QUERY_SCAN)==FTS5INDEX_QUERY_SCAN
  );

  if( sqlite3Fts5BufferGrow(&p->rc, &buf, nToken+1)==0 ){
    memcpy(&buf.p[1], pToken, nToken);
  }

#ifdef SQLITE_DEBUG
  if( flags & FTS5INDEX_QUERY_TEST_NOIDX ){
    assert( flags & FTS5INDEX_QUERY_PREFIX );
    iIdx = 1+pConfig->nPrefix;
  }else
#endif
  if( flags & FTS5INDEX_QUERY_PREFIX ){
    int nChar = fts5IndexCharlen(pToken, nToken);
    for(iIdx=1; iIdx<=pConfig->nPrefix; iIdx++){
      if( pConfig->aPrefix[iIdx-1]==nChar ) break;

    }
  }

  pRet = (Fts5IndexIter*)sqlite3Fts5MallocZero(&p->rc, sizeof(Fts5IndexIter));
  if( pRet ){


    pRet->pIndex = p;
    if( iIdx<=pConfig->nPrefix ){
      buf.p[0] = FTS5_MAIN_PREFIX + iIdx;
      pRet->pStruct = fts5StructureRead(p);
      if( pRet->pStruct ){
        fts5MultiIterNew(
            p, pRet->pStruct, 1, flags, buf.p, nToken+1, -1, 0, &pRet->pMulti

      pLvl->pData = 0;
    }
  }
  sqlite3_free(pIter->aLvl);
  fts5BufferFree(&pIter->term);
}

#ifdef SQLITE_DEBUG
/*
** This function is purely an internal test. It does not contribute to 
** FTS functionality, or even the integrity-check, in any way.
**
** Instead, it tests that the same set of pgno/rowid combinations are 
** visited regardless of whether the doclist-index identified by parameters
** iSegid/iLeaf is iterated in forwards or reverse order.
*/

static void fts5TestDlidxReverse(
  Fts5Index *p, 
  int iSegid,                     /* Segment id to load from */
  int iLeaf                       /* Load doclist-index for this leaf */
){
  Fts5DlidxIter *pDlidx = 0;
  u64 cksum1 = 13;
  u64 cksum2 = 13;

    cksum2 += iRowid + ((i64)pgno<<32);
  }
  fts5DlidxIterFree(pDlidx);
  pDlidx = 0;

  if( p->rc==SQLITE_OK && cksum1!=cksum2 ) p->rc = FTS5_CORRUPT;
}

static int fts5QueryCksum(
  Fts5Index *p,                   /* Fts5 index object */
  int iIdx,
  const char *z,                  /* Index key to query for */
  int n,                          /* Size of index key in bytes */
  int flags,                      /* Flags for Fts5IndexQuery */
  u64 *pCksum                     /* IN/OUT: Checksum value */
){
  u64 cksum = *pCksum;
  Fts5IndexIter *pIdxIter = 0;
  int rc = sqlite3Fts5IndexQuery(p, z, n, flags, &pIdxIter);

  while( rc==SQLITE_OK && 0==sqlite3Fts5IterEof(pIdxIter) ){
    const u8 *pPos;
    int nPos;
    i64 rowid = sqlite3Fts5IterRowid(pIdxIter);
    rc = sqlite3Fts5IterPoslist(pIdxIter, &pPos, &nPos);
    if( rc==SQLITE_OK ){
      Fts5PoslistReader sReader;
      for(sqlite3Fts5PoslistReaderInit(-1, pPos, nPos, &sReader);
          sReader.bEof==0;
          sqlite3Fts5PoslistReaderNext(&sReader)
      ){
        int iCol = FTS5_POS2COLUMN(sReader.iPos);
        int iOff = FTS5_POS2OFFSET(sReader.iPos);
        cksum ^= fts5IndexEntryCksum(rowid, iCol, iOff, iIdx, z, n);
      }
      rc = sqlite3Fts5IterNext(pIdxIter);
    }
  }
  sqlite3Fts5IterClose(pIdxIter);

  *pCksum = cksum;
  return rc;
}


/*
** This function is also purely an internal test. It does not contribute to 
** FTS functionality, or even the integrity-check, in any way.
*/
static void fts5TestTerm(
  Fts5Index *p, 
  Fts5Buffer *pPrev,              /* Previous term */
  const char *z, int n,           /* Possibly new term to test */
  u64 expected,
  u64 *pCksum
){
  int rc = p->rc;
  if( pPrev->n==0 ){
    fts5BufferSet(&rc, pPrev, n, (const u8*)z);
  }else
  if( rc==SQLITE_OK && (pPrev->n!=n || memcmp(pPrev->p, z, n)) ){
    u32 cksum3 = *pCksum;
    const char *zTerm = &pPrev->p[1];  /* The term without the prefix-byte */
    int nTerm = pPrev->n-1;            /* Size of zTerm in bytes */
    int iIdx = (pPrev->p[0] - FTS5_MAIN_PREFIX);
    int flags = (iIdx==0 ? 0 : FTS5INDEX_QUERY_PREFIX);
    int rc;
    u64 ck1 = 0;
    u64 ck2 = 0;

    /* Check that the results returned for ASC and DESC queries are
    ** the same. If not, call this corruption.  */
    rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, flags, &ck1);
    if( rc==SQLITE_OK ){
      int f = flags|FTS5INDEX_QUERY_DESC;
      rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, f, &ck2);
    }
    if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;

    /* If this is a prefix query, check that the results returned if the
    ** the index is disabled are the same. In both ASC and DESC order. */
    if( iIdx>0 && rc==SQLITE_OK ){
      int f = flags|FTS5INDEX_QUERY_TEST_NOIDX;
      ck2 = 0;
      rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, f, &ck2);
      if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;
    }
    if( iIdx>0 && rc==SQLITE_OK ){
      int f = flags|FTS5INDEX_QUERY_TEST_NOIDX|FTS5INDEX_QUERY_DESC;
      ck2 = 0;
      rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, f, &ck2);
      if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;
    }

    cksum3 ^= ck1;
    fts5BufferSet(&rc, pPrev, n, (const u8*)z);

    if( rc==SQLITE_OK && cksum3!=expected ){
      rc = FTS5_CORRUPT;
    }
    *pCksum = cksum3;
  }
  p->rc = rc;
}
 
#else
# define fts5TestDlidxReverse(x,y,z)
# define fts5TestTerm(u,v,w,x,y,z)
#endif

static void fts5IndexIntegrityCheckSegment(
  Fts5Index *p,                   /* FTS5 backend object */
  Fts5StructureSegment *pSeg      /* Segment to check internal consistency */
){
  Fts5BtreeIter iter;             /* Used to iterate through b-tree hierarchy */

        if( pLeaf ){
          if( fts5GetU16(&pLeaf->p[0])!=0 ) p->rc = FTS5_CORRUPT;
          fts5DataRelease(pLeaf);
        }
      }

      fts5DlidxIterFree(pDlidx);
      fts5TestDlidxReverse(p, iSegid, iter.iLeaf);
    }
  }

  /* Page iter.iLeaf must now be the rightmost leaf-page in the segment */


  if( p->rc==SQLITE_OK && iter.iLeaf!=pSeg->pgnoLast ){



    p->rc = FTS5_CORRUPT;
  }

  fts5BtreeIterFree(&iter);
}






































/*
** Run internal checks to ensure that the FTS index (a) is internally 
** consistent and (b) contains entries for which the XOR of the checksums
** as calculated by fts5IndexEntryCksum() is cksum.
**
** Return SQLITE_CORRUPT if any of the internal checks fail, or if the
** checksum does not match. Return SQLITE_OK if all checks pass without
** error, or some other SQLite error code if another error (e.g. OOM)
** occurs.
*/
int sqlite3Fts5IndexIntegrityCheck(Fts5Index *p, u64 cksum){
  u64 cksum2 = 0;                 /* Checksum based on contents of indexes */


  Fts5Buffer poslist = {0,0,0};   /* Buffer used to hold a poslist */
  Fts5MultiSegIter *pIter;        /* Used to iterate through entire index */
  Fts5Structure *pStruct;         /* Index structure */

  /* Used by extra internal tests only run if NDEBUG is not defined */
  u64 cksum3 = 0;                 /* Checksum based on contents of indexes */
  Fts5Buffer term = {0,0,0};      /* Buffer used to hold most recent term */
  
  /* Load the FTS index structure */
  pStruct = fts5StructureRead(p);

  /* Check that the internal nodes of each segment match the leaves */
  if( pStruct ){
    int iLvl, iSeg;

    while( 0==sqlite3Fts5PoslistNext64(poslist.p, poslist.n, &iOff, &iPos) ){
      int iCol = FTS5_POS2COLUMN(iPos);
      int iTokOff = FTS5_POS2OFFSET(iPos);
      cksum2 ^= fts5IndexEntryCksum(iRowid, iCol, iTokOff, -1, z, n);
    }

    /* If this is a new term, query for it. Update cksum3 with the results. */








    fts5TestTerm(p, &term, z, n, cksum2, &cksum3);






  }

  fts5TestTerm(p, &term, 0, 0, cksum2, &cksum3);




















  fts5MultiIterFree(p, pIter);

  if( p->rc==SQLITE_OK && cksum!=cksum2 ) p->rc = FTS5_CORRUPT;


  fts5StructureRelease(pStruct);
  fts5BufferFree(&term);
  fts5BufferFree(&poslist);
  return fts5IndexReturn(p);
}

  do_execsql_test 2.$i.4 {
    ROLLBACK;
    INSERT INTO t1(t1) VALUES('integrity-check');
  } {}
}



#-------------------------------------------------------------------------
# Test that corruption in leaf page headers is detected by queries that use
# doclist-indexes.
#
set doc "A B C D E F G H I J "
do_execsql_test 3.0 {
  CREATE VIRTUAL TABLE x3 USING fts5(tt);

    } {1}

    execsql ROLLBACK
  }

  do_test 4.$tn.x { expr $nCorrupt>0 } 1
}

}

set doc [string repeat "A B C " 1000]
do_execsql_test 4.0 {
  CREATE VIRTUAL TABLE x5 USING fts5(tt);
  INSERT INTO x5(x5, rank) VALUES('pgsz', 32);
  WITH ii(i) AS (SELECT 1 UNION ALL SELECT i+1 FROM ii WHERE i<10) 
  INSERT INTO x5 SELECT $doc FROM ii;
}

foreach {tn hdr} {
  1 "\x00\x01"
} {
  set tn2 0
  set nCorrupt 0
  foreach rowid [db eval {SELECT rowid FROM x5_data WHERE rowid>10}] {
    if {$rowid & $mask} continue
    incr tn2
    do_test 4.$tn.$tn2 {
      execsql BEGIN

      set fd [db incrblob main x5_data block $rowid]
      fconfigure $fd -encoding binary -translation binary
      puts -nonewline $fd $hdr
      close $fd

      catchsql { INSERT INTO x5(x5) VALUES('integrity-check') }
      set {} {}
    } {}

    execsql ROLLBACK
  }
}


sqlite3_fts5_may_be_corrupt 0
finish_test

# 2015 Apr 24
#
# 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 tests that FTS5 handles corrupt databases (i.e. internal
# inconsistencies in the backing tables) correctly. In this case 
# "correctly" means without crashing.
#

source [file join [file dirname [info script]] fts5_common.tcl]
set testprefix fts5corrupt3
sqlite3_fts5_may_be_corrupt 1

# Create a simple FTS5 table containing 100 documents. Each document 
# contains 10 terms, each of which start with the character "x".
#
expr srand(0)
db func rnddoc fts5_rnddoc
do_execsql_test 1.0 {
  CREATE VIRTUAL TABLE t1 USING fts5(x);
  INSERT INTO t1(t1, rank) VALUES('pgsz', 64);
  WITH ii(i) AS (SELECT 1 UNION SELECT i+1 FROM ii WHERE i<100)
  INSERT INTO t1 SELECT rnddoc(10) FROM ii;
}
set mask [expr 31 << 31]

do_test 1.1 {
  # Pick out the rowid of the right-most b-tree leaf in the new segment.
  set rowid [db one {
    SELECT max(rowid) FROM t1_data WHERE ((rowid>>31) & 0x0F)==1
  }]
  set L [db one {SELECT length(block) FROM t1_data WHERE rowid = $rowid}]
  set {} {}
} {} 

for {set i 0} {$i < $L} {incr i} {
  do_test 1.2.$i {
    catchsql {
      BEGIN;
      UPDATE t1_data SET block = substr(block, 1, $i) WHERE id = $rowid;
      INSERT INTO t1(t1) VALUES('integrity-check');
    }
  } {1 {database disk image is malformed}}
  catchsql ROLLBACK
}
 

sqlite3_fts5_may_be_corrupt 0
finish_test

do_test 3.4 {
  execsql { INSERT INTO x8(x8, rank) VALUES('automerge', 4) }
  while {[not_merged x8]} {
    execsql { INSERT INTO x8(x8, rank) VALUES('merge', 1) }
  }
  fts5_level_segs x8
} {0 1}

#-------------------------------------------------------------------------
#
proc mydoc {} {
  set x [lindex {a b c d e f g h i j} [expr int(rand()*10)]]
  return [string repeat "$x " 30]
}
db func mydoc mydoc

proc mycount {} {
  set res [list]
  foreach x {a b c d e f g h i j} {
    lappend res [db one {SELECT count(*) FROM x8 WHERE x8 MATCH $x}]
  }
  set res
}

  #1 32
foreach {tn pgsz} {
  2 1000
} {
  do_execsql_test 4.$tn.1 {
    DROP TABLE IF EXISTS x8;
    CREATE VIRTUAL TABLE x8 USING fts5(i);
    INSERT INTO x8(x8, rank) VALUES('pgsz', $pgsz);
  }

  do_execsql_test 4.$tn.2 {
    INSERT INTO x8(x8, rank) VALUES('merge', 1);
  }

  do_execsql_test 4.$tn.3 {
    WITH ii(i) AS (SELECT 1 UNION ALL SELECT i+1 FROM ii WHERE i<100)
      INSERT INTO x8 SELECT mydoc() FROM ii;
    WITH ii(i) AS (SELECT 1 UNION ALL SELECT i+1 FROM ii WHERE i<100)
      INSERT INTO x8 SELECT mydoc() FROM ii;
    INSERT INTO x8(x8, rank) VALUES('automerge', 2);
  }

  set expect [mycount]
    for {set i 0} {$i < 20} {incr i} {
      do_test 4.$tn.4.$i {
        execsql { INSERT INTO x8(x8, rank) VALUES('merge', 1); }
        mycount
      } $expect
      break
    }
  db eval {SELECT fts5_decode(rowid, block) AS r FROM x8_data} { puts $r }
}

finish_test