SQLite

#define sqlite3Fts5IterEof(x) ((x)->bEof)

/*
** Values used as part of the flags argument passed to IndexQuery().
*/
#define FTS5INDEX_QUERY_PREFIX     0x0001   /* Prefix query */
#define FTS5INDEX_QUERY_DESC       0x0002   /* Docs in descending rowid order */

#define FTS5INDEX_QUERY_SCAN       0x0008   /* Scan query (fts5vocab) */

/* The following are used internally by the fts5_index.c module. They are
** defined here only to make it easier to avoid clashes with the flags
** above. */
#define FTS5INDEX_QUERY_SKIPEMPTY  0x0010
#define FTS5INDEX_QUERY_NOOUTPUT   0x0020

  /* In-memory cache of the 'structure' record */
  sqlite3_stmt *pDataVersion;     /* PRAGMA <db>.data_version */
  i64 iStructVersion;             /* data_version when pStruct read */
  Fts5Structure *pStruct;         /* Current db structure (or NULL) */
};

/*
** An iterator of this sort is used to iterate through a doclist stored
** entirely in memory. See functions fts5DoclistIterInit() and
** fts5DoclistIterNext() for details. 
*/
struct Fts5DoclistIter {
  u8 *aEof;                       /* Pointer to 1 byte past end of doclist */

  /* Output variables. aPoslist==0 at EOF */
  i64 iRowid;
  u8 *aPoslist;
  int nPoslist;

  u8 bSkipEmpty;                  /* True to skip deleted entries */

  i64 iSwitchRowid;               /* Firstest rowid of other than aFirst[1] */
  Fts5CResult *aFirst;            /* Current merge state (see above) */
  Fts5SegIter aSeg[1];            /* Array of segment iterators */
};


/*
** Given pointer "x" to an Fts5Iter structure, return a pointer the the
** current first component segment iterator.
*/
#define fts5IterSegment(x) (&(x)->aSeg [ (x)->aFirst[1].iFirst ])


/*
** An instance of the following type is used to iterate through the contents
** of a doclist-index record.
**
** pData:
**   Record containing the doclist-index data.

/*
** Return true if the iterator passed as the second argument currently
** points to a delete marker. A delete marker is an entry with a 0 byte
** position-list.
*/
static int fts5MultiIterIsEmpty(Fts5Index *p, Fts5Iter *pIter){
  Fts5SegIter *pSeg = fts5IterSegment(pIter);
  return (p->rc==SQLITE_OK && pSeg->pLeaf && pSeg->nPos==0);
}

/*
** Advance iterator pIter to the next entry.
**
** This version of fts5SegIterNext() is only used by reverse iterators.

** This function is a no-op unless SQLITE_DEBUG is defined when this module
** is compiled. In that case, this function is essentially an assert() 
** statement used to verify that the contents of the pIter->aFirst[] array
** are correct.
*/
static void fts5AssertMultiIterSetup(Fts5Index *p, Fts5Iter *pIter){
  if( p->rc==SQLITE_OK ){
    Fts5SegIter *pFirst = fts5IterSegment(pIter);
    int i;

    assert( (pFirst->pLeaf==0)==pIter->base.bEof );

    /* Check that pIter->iSwitchRowid is set correctly. */
    for(i=0; i<pIter->nSeg; i++){
      Fts5SegIter *p1 = &pIter->aSeg[i];

  return 0;
}

/*
** Set the pIter->bEof variable based on the state of the sub-iterators.
*/
static void fts5MultiIterSetEof(Fts5Iter *pIter){
  Fts5SegIter *pSeg = fts5IterSegment(pIter);
  pIter->base.bEof = pSeg->pLeaf==0;
  pIter->iSwitchRowid = pSeg->iRowid;
}

/*
** Move the iterator to the next entry. 
**

    }

    if( pSeg->pLeaf==0 || bNewTerm 
     || fts5MultiIterAdvanceRowid(pIter, iFirst, &pSeg)
    ){
      fts5MultiIterAdvanced(p, pIter, iFirst, 1);
      fts5MultiIterSetEof(pIter);
      pSeg = fts5IterSegment(pIter);
      if( pSeg->pLeaf==0 ) return;
    }

    fts5AssertMultiIterSetup(p, pIter);
    assert( pSeg==fts5IterSegment(pIter) && pSeg->pLeaf );
    if( pIter->bSkipEmpty==0 || pSeg->nPos ){
      pIter->xSetOutputs(pIter, pSeg);
      return;
    }
    bUseFrom = 0;
  }
}

    }
    fts5MultiIterSetEof(pNew);
    fts5AssertMultiIterSetup(p, pNew);

    if( pNew->bSkipEmpty && fts5MultiIterIsEmpty(p, pNew) ){
      fts5MultiIterNext(p, pNew, 0, 0);
    }else if( pNew->base.bEof==0 ){

      pNew->xSetOutputs(pNew, fts5IterSegment(pNew));
    }

  }else{
    fts5MultiIterFree(pNew);
    *ppOut = 0;
  }
}

}

/*
** Return true if the iterator is at EOF or if an error has occurred. 
** False otherwise.
*/
static int fts5MultiIterEof(Fts5Index *p, Fts5Iter *pIter){
  assert( p->rc || (fts5IterSegment(pIter)->pLeaf==0)==pIter->base.bEof );


  return (p->rc || pIter->base.bEof);
}

/*
** Return the rowid of the entry that the iterator currently points
** to. If the iterator points to EOF when this function is called the
** results are undefined.
*/
static i64 fts5MultiIterRowid(Fts5Iter *pIter){
  assert( fts5IterSegment(pIter)->pLeaf );
  return fts5IterSegment(pIter)->iRowid;
}

/*
** Move the iterator to the next entry at or following iMatch.
*/
static void fts5MultiIterNextFrom(
  Fts5Index *p, 

}

static void fts5WriteFlushLeaf(Fts5Index *p, Fts5SegWriter *pWriter){
  static const u8 zero[] = { 0x00, 0x00, 0x00, 0x00 };
  Fts5PageWriter *pPage = &pWriter->writer;
  i64 iRowid;




  assert( (pPage->pgidx.n==0)==(pWriter->bFirstTermInPage) );

  /* Set the szLeaf header field. */
  assert( 0==fts5GetU16(&pPage->buf.p[2]) );
  fts5PutU16(&pPage->buf.p[2], (u16)pPage->buf.n);

  if( pWriter->bFirstTermInPage ){

  const u8 *pChunk, int nChunk
){
  Fts5SegWriter *pWriter = (Fts5SegWriter*)pCtx;
  fts5WriteAppendPoslistData(p, pWriter, pChunk, nChunk);
}

/*
** This function reads data from level iLvl of structure (*ppStruct) and
** writes it into a segment on level (iLvl+1). If (*ppStruct) indicates
** that there is already such a merge underway, this function continues
** it. Otherwise, a new merge is started. (*ppStruct) is updated with the
** results of the merge before this function returns.
**
** When this function is called in/out parameter *pnRem contains the maximum
** number of leaf pages to write to the database. *pnRem is decremented by
** the actual number of pages written before this function returns.
*/
static void fts5IndexMergeLevel(
  Fts5Index *p,                   /* FTS5 backend object */
  Fts5Structure **ppStruct,       /* IN/OUT: Stucture of index */
  int iLvl,                       /* Level to read input from */
  int *pnRem                      /* IN/OUT: Write this many output leaves */
){
  Fts5Structure *pStruct = *ppStruct;
  Fts5StructureLevel *pLvl = &pStruct->aLevel[iLvl];
  Fts5StructureLevel *pLvlOut;
  Fts5Iter *pIter = 0;       /* Iterator to read input data */
  int nRem = pnRem ? *pnRem : 0;  /* Output leaf pages left to write */
  int nInput;                     /* Number of input segments */

  bOldest = (pLvlOut->nSeg==1 && pStruct->nLevel==iLvl+2);

  assert( iLvl>=0 );
  for(fts5MultiIterNew(p, pStruct, flags, 0, 0, 0, iLvl, nInput, &pIter);
      fts5MultiIterEof(p, pIter)==0;
      fts5MultiIterNext(p, pIter, 0, 0)
  ){
    Fts5SegIter *pSegIter = fts5IterSegment(pIter);
    int nPos;                     /* position-list size field value */
    int nTerm;
    const u8 *pTerm;

    /* Check for key annihilation. */
    if( pSegIter->nPos==0 && (bOldest || pSegIter->bDel==0) ) continue;

    pStruct->nWriteCounter += nLeaf;
    nRem = (int)(p->nWorkUnit * nWork * pStruct->nLevel);

    fts5IndexMerge(p, ppStruct, nRem, p->pConfig->nAutomerge);
  }
}

/*
** This function is called when a new level 0 segment has just been written
** to the database. If any crisis-merge operations are required as a result,
** they are performed here.
*/
static void fts5IndexCrisismerge(
  Fts5Index *p,                   /* FTS5 backend object */
  Fts5Structure **ppStruct        /* IN/OUT: Current structure of index */
){
  const int nCrisis = p->pConfig->nCrisisMerge;
  Fts5Structure *pStruct = *ppStruct;
  int iLvl = 0;

  assert( p->rc!=SQLITE_OK || pStruct->nLevel>0 );
  while( p->rc==SQLITE_OK && pStruct->aLevel[iLvl].nSeg>=nCrisis ){
    fts5IndexMergeLevel(p, &pStruct, iLvl, 0);
    assert( p->rc!=SQLITE_OK || pStruct->nLevel>(iLvl+1) );
    fts5StructurePromote(p, iLvl+1, pStruct);
    iLvl++;
  }
  *ppStruct = pStruct;
}







/*
** Buffer aBuf[] contains a list of varints, all small enough to fit
** in a 32-bit integer. Return the size of the largest prefix of this 
** list nMax bytes or less in size.
*/
static int fts5PoslistPrefix(const u8 *aBuf, int nMax){
  int ret;
  u32 dummy;
  ret = fts5GetVarint32(aBuf, dummy);
  if( ret<nMax ){
    while( 1 ){
      int i = fts5GetVarint32(&aBuf[ret], dummy);
      if( (ret + i) > nMax ) break;
      ret += i;
    }
  }
  return ret;
}

/*
** Flush any data stored in the in-memory hash tables to the database.

**
** If an error occurs, set the Fts5Index.rc error code. If an error has 
** already occurred, this function is a no-op.
*/
static void fts5IndexFlush(Fts5Index *p){
  if( p->nPendingData ){
    Fts5Hash *pHash = p->pHash;
    Fts5Structure *pStruct;
    int iSegid;
    int pgnoLast = 0;                 /* Last leaf page number in segment */

    p->nPendingData = 0;

    /* Obtain a reference to the index structure and allocate a new segment-id
    ** for the new level-0 segment.  */
    pStruct = fts5StructureRead(p);
    iSegid = fts5AllocateSegid(p, pStruct);
    fts5StructureInvalidate(p);

    if( iSegid ){
      const int pgsz = p->pConfig->pgsz;
      int eDetail = p->pConfig->eDetail;
      Fts5StructureSegment *pSeg;   /* New segment within pStruct */
      Fts5Buffer *pBuf;             /* Buffer in which to assemble leaf page */
      Fts5Buffer *pPgidx;           /* Buffer in which to assemble pgidx */

      Fts5SegWriter writer;
      fts5WriteInit(p, &writer, iSegid);

      pBuf = &writer.writer.buf;
      pPgidx = &writer.writer.pgidx;

      /* fts5WriteInit() should have initialized the buffers to (most likely)
      ** the maximum space required. */
      assert( p->rc || pBuf->nSpace>=(pgsz + FTS5_DATA_PADDING) );
      assert( p->rc || pPgidx->nSpace>=(pgsz + FTS5_DATA_PADDING) );

      /* Begin scanning through hash table entries. This loop runs once for each
      ** term/doclist currently stored within the hash table. */
      if( p->rc==SQLITE_OK ){
        p->rc = sqlite3Fts5HashScanInit(pHash, 0, 0);
      }
      while( p->rc==SQLITE_OK && 0==sqlite3Fts5HashScanEof(pHash) ){
        const char *zTerm;          /* Buffer containing term */
        const u8 *pDoclist;         /* Pointer to doclist for this term */
        int nDoclist;               /* Size of doclist in bytes */

        /* Write the term for this entry to disk. */
        sqlite3Fts5HashScanEntry(pHash, &zTerm, &pDoclist, &nDoclist);
        fts5WriteAppendTerm(p, &writer, (int)strlen(zTerm), (const u8*)zTerm);

        assert( writer.bFirstRowidInPage==0 );
        if( pgsz>=(pBuf->n + pPgidx->n + nDoclist + 1) ){
          /* The entire doclist will fit on the current leaf. */
          fts5BufferSafeAppendBlob(pBuf, pDoclist, nDoclist);
        }else{
          i64 iRowid = 0;
          i64 iDelta = 0;
          int iOff = 0;

          /* The entire doclist will not fit on this leaf. The following 
          ** loop iterates through the poslists that make up the current 
          ** doclist.  */
          while( p->rc==SQLITE_OK && iOff<nDoclist ){
            iOff += fts5GetVarint(&pDoclist[iOff], (u64*)&iDelta);
            iRowid += iDelta;
            
            if( writer.bFirstRowidInPage ){
              fts5PutU16(&pBuf->p[0], (u16)pBuf->n);   /* first rowid on page */
              pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], iRowid);
              writer.bFirstRowidInPage = 0;
              fts5WriteDlidxAppend(p, &writer, iRowid);
            }else{
              pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], iDelta);
            }
            assert( pBuf->n<=pBuf->nSpace );

            if( eDetail==FTS5_DETAIL_NONE ){
              if( iOff<nDoclist && pDoclist[iOff]==0 ){
                pBuf->p[pBuf->n++] = 0;
                iOff++;
                if( iOff<nDoclist && pDoclist[iOff]==0 ){
                  pBuf->p[pBuf->n++] = 0;
                  iOff++;
                }
              }
              if( (pBuf->n + pPgidx->n)>=pgsz ){
                fts5WriteFlushLeaf(p, &writer);
              }
            }else{
              int bDummy;
              int nPos;
              int nCopy = fts5GetPoslistSize(&pDoclist[iOff], &nPos, &bDummy);
              nCopy += nPos;
              if( (pBuf->n + pPgidx->n + nCopy) <= pgsz ){
                /* The entire poslist will fit on the current leaf. So copy
                ** it in one go. */
                fts5BufferSafeAppendBlob(pBuf, &pDoclist[iOff], nCopy);
              }else{
                /* The entire poslist will not fit on this leaf. So it needs
                ** to be broken into sections. The only qualification being
                ** that each varint must be stored contiguously.  */
                const u8 *pPoslist = &pDoclist[iOff];
                int iPos = 0;
                while( p->rc==SQLITE_OK ){
                  int nSpace = pgsz - pBuf->n - pPgidx->n;
                  int n = 0;
                  if( (nCopy - iPos)<=nSpace ){
                    n = nCopy - iPos;
                  }else{
                    n = fts5PoslistPrefix(&pPoslist[iPos], nSpace);
                  }
                  assert( n>0 );
                  fts5BufferSafeAppendBlob(pBuf, &pPoslist[iPos], n);
                  iPos += n;
                  if( (pBuf->n + pPgidx->n)>=pgsz ){
                    fts5WriteFlushLeaf(p, &writer);
                  }
                  if( iPos>=nCopy ) break;
                }
              }
              iOff += nCopy;
            }
          }
        }

        /* TODO2: Doclist terminator written here. */
        /* pBuf->p[pBuf->n++] = '\0'; */
        assert( pBuf->n<=pBuf->nSpace );
        sqlite3Fts5HashScanNext(pHash);
      }
      sqlite3Fts5HashClear(pHash);
      fts5WriteFinish(p, &writer, &pgnoLast);

      /* Update the Fts5Structure. It is written back to the database by the
      ** fts5StructureRelease() call below.  */
      if( pStruct->nLevel==0 ){
        fts5StructureAddLevel(&p->rc, &pStruct);
      }
      fts5StructureExtendLevel(&p->rc, pStruct, 0, 1, 0);
      if( p->rc==SQLITE_OK ){
        pSeg = &pStruct->aLevel[0].aSeg[ pStruct->aLevel[0].nSeg++ ];
        pSeg->iSegid = iSegid;
        pSeg->pgnoFirst = 1;
        pSeg->pgnoLast = pgnoLast;
        pStruct->nSegment++;
      }
      fts5StructurePromote(p, 0, pStruct);
    }

    fts5IndexAutomerge(p, &pStruct, pgnoLast);
    fts5IndexCrisismerge(p, &pStruct);
    fts5StructureWrite(p, pStruct);
    fts5StructureRelease(pStruct);
  }
}

/*

** If argument pStruct contains fewer than two segments, NULL is returned.
**
** Otherwise, this function returns a structure reference containing all the
** same segments as argument pStruct, but arranged within levels so that
** running the merge sub-routines merges all content into a single segment.
*/









static Fts5Structure *fts5IndexOptimizeStruct(
  Fts5Index *p,                   /* Index object */
  Fts5Structure *pStruct          /* Structure to optimize */
){
  Fts5Structure *pNew = 0;
  int nByte = sizeof(Fts5Structure);
  int nSeg = pStruct->nSegment;
  int i;

  /* First figure out if this structure requires optimization. A structure 
  ** does not require optimization if either:
  **
  **  + it consists of fewer than two segments, or 
  **  + all segments are on the same level, or
  **  + all segments except one are currently inputs to a merge operation.
  **
  ** In the first case, return NULL. In the second and third, increment the
  ** ref-count on *pStruct and return a copy of the pointer to it.  */

  if( nSeg<2 ) return 0;
  for(i=0; i<pStruct->nLevel; i++){
    int nThis = pStruct->aLevel[i].nSeg;
    if( nThis==nSeg || (nThis==nSeg-1 && pStruct->aLevel[i].nMerge==nThis) ){
      fts5StructureRef(pStruct);
      return pStruct;
    }
    assert( pStruct->aLevel[i].nMerge<=nThis );
  }

  /* Allocate a new structure. Copy all segments from pStruct to level nMax+1
  ** of the new structure, where nMax is the largest level in pStruct.  */
  nByte += (pStruct->nLevel+1) * sizeof(Fts5StructureLevel);
  pNew = (Fts5Structure*)sqlite3Fts5MallocZero(&p->rc, nByte);

  if( pNew ){
    Fts5StructureLevel *pLvl;
    nByte = nSeg * sizeof(Fts5StructureSegment);
    pNew->nLevel = pStruct->nLevel+1;
    pNew->nRef = 1;
    pNew->nWriteCounter = pStruct->nWriteCounter;
    pLvl = &pNew->aLevel[pStruct->nLevel];

      pNew = 0;
    }
  }

  return pNew;
}

/*
** Return from an Fts5Index API function that may have set the error code.
*/
static int fts5IndexReturn(Fts5Index *p){
  int rc = p->rc;
  p->rc = SQLITE_OK;
  return rc;
}

/*
** The implementation of the special "VALUES('optimize')" command.
*/
int sqlite3Fts5IndexOptimize(Fts5Index *p){
  Fts5Structure *pStruct;
  Fts5Structure *pNew = 0;

  assert( p->rc==SQLITE_OK );
  fts5IndexFlush(p);
  pStruct = fts5StructureRead(p);

      }
    }
    fts5StructureRelease(pStruct);
  }
  return fts5IndexReturn(p);
}

/*
** Append varint iDelta to buffer pBuf.
**
** This function is a no-op if Fts5Index.rc is set to other than SQLITE_OK
** when it is called. If an error occurs, Fts5Index.rc is set to an SQLite
** error code before returning.
*/
static void fts5AppendRowid(
  Fts5Index *p,
  i64 iDelta,
  Fts5Iter *pUnused,
  Fts5Buffer *pBuf
){
  UNUSED_PARAM(pUnused);
  fts5BufferAppendVarint(&p->rc, pBuf, iDelta);
}

/*
** Append varint iDelta to buffer pBuf. Then append a copy of the poslist
** currently pointed to by iterator pMulti.
**
** This function is a no-op if Fts5Index.rc is set to other than SQLITE_OK
** when it is called. If an error occurs, Fts5Index.rc is set to an SQLite
** error code before returning.
*/
static void fts5AppendPoslist(
  Fts5Index *p,
  i64 iDelta,
  Fts5Iter *pMulti,
  Fts5Buffer *pBuf
){
  int nData = pMulti->base.nData;
  assert( nData>0 );
  if( p->rc==SQLITE_OK && 0==fts5BufferGrow(&p->rc, pBuf, nData+9+9) ){
    fts5BufferSafeAppendVarint(pBuf, iDelta);
    fts5BufferSafeAppendVarint(pBuf, nData*2);
    fts5BufferSafeAppendBlob(pBuf, pMulti->base.pData, nData);
  }
}

/*
** Advance iterator pIter to the next rowid in its doclist.
*/
static void fts5DoclistIterNext(Fts5DoclistIter *pIter){
  u8 *p = pIter->aPoslist + pIter->nSize + pIter->nPoslist;

  assert( pIter->aPoslist );
  if( p>=pIter->aEof ){
    pIter->aPoslist = 0;
  }else{

      pIter->nSize = 1;
    }

    pIter->aPoslist = p;
  }
}

/*
** Buffer pBuf contains a doclist. Set up the structure pointed to by 
** pIter to iterate through it. The iterator points to the first rowid
** in the doclist (or EOF if the doclist is empty) when this function
** returns.
*/
static void fts5DoclistIterInit(
  Fts5Buffer *pBuf, 
  Fts5DoclistIter *pIter
){
  memset(pIter, 0, sizeof(*pIter));
  pIter->aPoslist = pBuf->p;
  pIter->aEof = &pBuf->p[pBuf->n];
  fts5DoclistIterNext(pIter);
}

























/*
** Swap the contents of buffer *p1 with that of *p2.
*/
static void fts5BufferSwap(Fts5Buffer *p1, Fts5Buffer *p2){
  Fts5Buffer tmp = *p1;
  *p1 = *p2;
  *p2 = tmp;
}

/*
** Buffer pBuf contains a delta-encoded list of rowids (the sort stored by
** detail=none tables). 
**
** When this function is called, *piOff must be set to the byte offset of a
** varint within this list, and *piRowid to the value of the previous
** rowid in the list. If there are no more rowids in the list, *piOff is
** set to -1 before returning. Otherwise, *piRowid is set to the next
** rowid in the list and *piOff to the offset of the rowid following it.
*/
static void fts5NextRowid(Fts5Buffer *pBuf, int *piOff, i64 *piRowid){
  int i = *piOff;
  if( i>=pBuf->n ){
    *piOff = -1;
  }else{
    u64 iVal;
    *piOff = i + sqlite3Fts5GetVarint(&pBuf->p[i], &iVal);

      fts5NextRowid(p2, &i2, &iRowid2);
    }
  }

  fts5BufferSwap(&out, p1);
  fts5BufferFree(&out);
}

/*
** This macro is used by fts5MergePrefixLists(). The arguments passed should 
** be of the following types:
**
**   Fts5Buffer *pBuf,            // Buffer to write to
**   i64 iLastRowid,              // IN/OUT: Previous rowid written (if any)
**   i64 iRowid                   // Rowid to append
**
** This function appends a single rowid to the doclist stored in pBuf. The
** value of the rowid appended is iRowid. IN/OUT parameter iLastRowid
** should be set to the value of the previous rowid stored in the doclist
** when this macro is invoked. It is set to a copy of iRowid by this macro.
*/
#define fts5MergeAppendDocid(pBuf, iLastRowid, iRowid) {       \
  assert( (pBuf)->n!=0 || (iLastRowid)==0 );                   \
  fts5BufferSafeAppendVarint((pBuf), (iRowid) - (iLastRowid)); \
  (iLastRowid) = (iRowid);                                     \
}

/*
** Buffers p1 and p2 contain doclists. This function merges the content
** of the two doclists together and sets buffer p1 to the result before
** returning.
**
** If an error occurs, an error code is left in p->rc. If an error has

    fts5BufferSet(&p->rc, p1, out.n, out.p);
    fts5BufferFree(&tmp);
    fts5BufferFree(&out);
  }
}

/*
** This function is used to prepare an iterator for a prefix query for
** which there is no prefix index. It assembles a doclist in memory
** and then sets up an Fts5Iter object to iterate through it.
*/
static void fts5SetupPrefixIter(
  Fts5Index *p,                   /* Index to read from */
  int bDesc,                      /* True for "ORDER BY rowid DESC" */
  const u8 *pToken,               /* Buffer containing prefix to match */
  int nToken,                     /* Size of buffer pToken in bytes */
  Fts5Colset *pColset,            /* Restrict matches to these columns */
  Fts5Iter **ppIter               /* OUT: New iterator */
){
  Fts5Structure *pStruct;
  Fts5Buffer *aBuf;
  const int nBuf = 32;

  void (*xMerge)(Fts5Index*, Fts5Buffer*, Fts5Buffer*);
  void (*xAppend)(Fts5Index*, i64, Fts5Iter*, Fts5Buffer*);

    memset(&doclist, 0, sizeof(doclist));
    fts5MultiIterNew(p, pStruct, flags, pColset, pToken, nToken, -1, 0, &p1);
    fts5IterSetOutputCb(&p->rc, p1);
    for( /* no-op */ ;
        fts5MultiIterEof(p, p1)==0;
        fts5MultiIterNext2(p, p1, &bNewTerm)
    ){
      Fts5SegIter *pSeg = fts5IterSegment(p1);
      int nTerm = pSeg->term.n;
      const u8 *pTerm = pSeg->term.p;
      p1->xSetOutputs(p1, pSeg);

      assert_nc( memcmp(pToken, pTerm, MIN(nToken, nTerm))<=0 );
      if( bNewTerm ){
        if( nTerm<nToken || memcmp(pToken, pTerm, nToken) ) break;

  p->pConfig->iCookie = -1;
  /* assert( p->rc==SQLITE_OK ); */
  return SQLITE_OK;
}

/*
** The %_data table is completely empty when this function is called. This
** function populates it with the initial structure object and the initial
** version of the "averages" record (a zero-byte blob).
*/
int sqlite3Fts5IndexReinit(Fts5Index *p){
  Fts5Structure s;
  fts5StructureInvalidate(p);
  memset(&s, 0, sizeof(Fts5Structure));
  fts5DataWrite(p, FTS5_AVERAGES_ROWID, (const u8*)"", 0);
  fts5StructureWrite(p, &s);

  Fts5Index *p;                   /* New object */

  *pp = p = (Fts5Index*)sqlite3Fts5MallocZero(&rc, sizeof(Fts5Index));
  if( rc==SQLITE_OK ){
    p->pConfig = pConfig;
    p->nWorkUnit = FTS5_WORK_UNIT;
    p->zDataTbl = sqlite3Fts5Mprintf(&rc, "%s_data", pConfig->zName);
    if( bCreate ){
      if( rc==SQLITE_OK ){
        rc = sqlite3Fts5CreateTable(
            pConfig, "data", "id INTEGER PRIMARY KEY, block BLOB", 0, pzErr
        );
      }
      if( rc==SQLITE_OK ){
        rc = sqlite3Fts5CreateTable(pConfig, "idx", 
            "segid, term, pgno, PRIMARY KEY(segid, term)", 1, pzErr

        );
      }
      if( rc==SQLITE_OK ){
        rc = sqlite3Fts5IndexReinit(p);
      }
    }
  }

  assert( (iCol<0)==p->bDelete );

  /* Add the entry to the main terms index. */
  rc = sqlite3Fts5HashWrite(
      p->pHash, p->iWriteRowid, iCol, iPos, FTS5_MAIN_PREFIX, pToken, nToken
  );

  /* Add an entry for each of the prefix indexes that the token is large
  ** enough for (e.g. for which nChar>=nPrefix). */
  for(i=0; i<pConfig->nPrefix && rc==SQLITE_OK; i++){
    const int nChar = pConfig->aPrefix[i];
    int nByte = sqlite3Fts5IndexCharlenToBytelen(pToken, nToken, nChar);
    if( nByte ){
      rc = sqlite3Fts5HashWrite(p->pHash, 
          p->iWriteRowid, iCol, iPos, (char)(FTS5_MAIN_PREFIX+i+1), pToken,
          nByte

  Fts5Colset *pColset,            /* Match these columns only */
  Fts5IndexIter **ppIter          /* OUT: New iterator object */
){
  Fts5Config *pConfig = p->pConfig;
  Fts5Iter *pRet = 0;
  Fts5Buffer buf = {0, 0, 0};

  /* If the QUERY_SCAN flag is set, all other flags must be clear. This
  ** flag is used by the fts5vocab module only. */
  assert( (flags & FTS5INDEX_QUERY_SCAN)==0 || flags==FTS5INDEX_QUERY_SCAN );

  if( sqlite3Fts5BufferSize(&p->rc, &buf, nToken+1)==0 ){
    int iIdx = 0;                 /* Index to search */
    memcpy(&buf.p[1], pToken, nToken);

    /* Figure out which index to search and set iIdx accordingly. If this
    ** is a prefix query for which there is no prefix index, set iIdx to
    ** greater than pConfig->nPrefix to indicate that the query will be
    ** satisfied by scanning multiple terms in the main index.
    **
    ** If the Fts5Config.bPrefixIndex debugging flag is set, do not use
    ** a prefix index even if a suitable one does exist.  */









    if( flags & FTS5INDEX_QUERY_PREFIX ){
      int nChar = fts5IndexCharlen(pToken, nToken);
      for(iIdx=1; iIdx<=pConfig->nPrefix; iIdx++){
        if( pConfig->aPrefix[iIdx-1]==nChar ) break;
      }
#ifdef SQLITE_DEBUG
      if( pConfig->bPrefixIndex==0 ) iIdx = 1+pConfig->nPrefix;
#endif
    }

    if( iIdx<=pConfig->nPrefix ){
      /* Straight index lookup */
      Fts5Structure *pStruct = fts5StructureRead(p);
      buf.p[0] = (u8)(FTS5_MAIN_PREFIX + iIdx);
      if( pStruct ){
        fts5MultiIterNew(p, pStruct, flags | FTS5INDEX_QUERY_SKIPEMPTY, 
            pColset, buf.p, nToken+1, -1, 0, &pRet
        );
        fts5StructureRelease(pStruct);
      }
    }else{
      /* Scan multiple terms in the main index */
      int bDesc = (flags & FTS5INDEX_QUERY_DESC)!=0;
      buf.p[0] = FTS5_MAIN_PREFIX;
      fts5SetupPrefixIter(p, bDesc, buf.p, nToken+1, pColset, &pRet);
      assert( p->rc!=SQLITE_OK || pRet->pColset==0 );
      fts5IterSetOutputCb(&p->rc, pRet);
      if( p->rc==SQLITE_OK ){
        Fts5SegIter *pSeg = fts5IterSegment(pRet);
        if( pSeg->pLeaf ) pRet->xSetOutputs(pRet, pSeg);
      }
    }

    if( p->rc ){
      sqlite3Fts5IterClose(&pRet->base);
      pRet = 0;
      sqlite3Fts5IndexCloseReader(p);
    }

    *ppIter = &pRet->base;
    sqlite3Fts5BufferFree(&buf);
  }
  return fts5IndexReturn(p);
}




/*
** Move to the next matching rowid. 
*/
int sqlite3Fts5IterNext(Fts5IndexIter *pIndexIter){
  Fts5Iter *pIter = (Fts5Iter*)pIndexIter;
  assert( pIter->pIndex->rc==SQLITE_OK );
  fts5MultiIterNext(pIter->pIndex, pIter, 0, 0);

  Fts5Iter *pIter = (Fts5Iter*)pIndexIter;
  Fts5Index *p = pIter->pIndex;

  assert( pIter->pIndex->rc==SQLITE_OK );

  fts5MultiIterNext(p, pIter, 0, 0);
  if( p->rc==SQLITE_OK ){
    Fts5SegIter *pSeg = fts5IterSegment(pIter);
    if( pSeg->pLeaf && pSeg->term.p[0]!=FTS5_MAIN_PREFIX ){
      fts5DataRelease(pSeg->pLeaf);
      pSeg->pLeaf = 0;
      pIter->base.bEof = 1;
    }
  }

  Fts5Iter *pIter = (Fts5Iter*)pIndexIter;
  fts5MultiIterNextFrom(pIter->pIndex, pIter, iMatch);
  return fts5IndexReturn(pIter->pIndex);
}

/*
** Return the current term.
**
** This function is only called as part of the fts5vocab module - not as
** part of normal full-text query processing.
*/
const char *sqlite3Fts5IterTerm(Fts5IndexIter *pIndexIter, int *pn){
  int n;
  const char *z = (const char*)fts5MultiIterTerm((Fts5Iter*)pIndexIter, &n);
  *pn = n-1;
  return &z[1];
}

  fts5DataRelease(pData);
  return fts5IndexReturn(p);
}

/*
** Replace the current "averages" record with the contents of the buffer 
** supplied as the second argument. 
**
** The averages record consists of N+1 varints, where N is the number of
** columns in the fts5 table. The first varint is the total number of
** rows in the FTS table. The second varint is the total number of tokens 
** in the first column of the table, and so on.
*/
int sqlite3Fts5IndexSetAverages(Fts5Index *p, const u8 *pData, int nData){
  assert( p->rc==SQLITE_OK );
  fts5DataWrite(p, FTS5_AVERAGES_ROWID, pData, nData);
  return fts5IndexReturn(p);
}

/*
** Return the total number of blocks this module has read from the %_data
** table (since it was created by sqlite3Fts5IndexOpen).
*/
int sqlite3Fts5IndexReads(Fts5Index *p){
  return p->nRead;
}

/*
** Increment the value of the configuration cookie stored as the first 
** 32-bits of the structure record in the database. This is called after
** modifying the contents of the %_config table.
*/
int sqlite3Fts5IndexIncrCookie(Fts5Index *p){
  Fts5Structure *pStruct;
  pStruct = fts5StructureRead(p);
  p->pConfig->iCookie++;
  fts5StructureWrite(p, pStruct);
  fts5StructureRelease(pStruct);
  return fts5IndexReturn(p);
}

/*
** Ensure the contents of the %_config table have been loaded into memory.
*/
int sqlite3Fts5IndexLoadConfig(Fts5Index *p){
  fts5StructureCache(p);
  return fts5IndexReturn(p);
}

/*
** This is called when a new read or write transaction may be being opened.
** It ensures that the in-memory cache of the structure record is valid.
*/
int sqlite3Fts5IndexNewTrans(Fts5Index *p){
  assert( p->pStruct==0 || p->iStructVersion!=0 );
  if( p->pConfig->iCookie<0 || fts5IndexDataVersion(p)!=p->iStructVersion ){
    fts5StructureInvalidate(p);
  }
  return fts5IndexReturn(p);
}

    ** the index is disabled are the same. In both ASC and DESC order. 
    **
    ** This check may only be performed if the hash table is empty. This
    ** is because the hash table only supports a single scan query at
    ** a time, and the multi-iter loop from which this function is called
    ** is already performing such a scan. */
    if( p->nPendingData==0 ){
      int bSaved = p->pConfig->bPrefixIndex;
      p->pConfig->bPrefixIndex = 1;
      if( iIdx>0 && rc==SQLITE_OK ){

        ck2 = 0;
        rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, flags, &ck2);
        if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;
      }
      if( iIdx>0 && rc==SQLITE_OK ){

        ck2 = 0;
        rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, flags, &ck2);
        if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;
      }
      p->pConfig->bPrefixIndex = bSaved;
    }

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

    if( rc==SQLITE_OK && cksum3!=expected ){
      rc = FTS5_CORRUPT;

    ROLLBACK TO one;
  COMMIT;
}

do_execsql_test 1.2 {
  INSERT INTO t1(t1) VALUES('integrity-check');
}

#-------------------------------------------------------------------------
# Test that the in-memory configuration does not become inconsistent with
# respect to the on-disk configuration if a savepoint is rolled back.
#
proc posrowid {cmd} { $cmd xRowid }
proc negrowid {cmd} { expr -1 * [$cmd xRowid] }
sqlite3_fts5_create_function db posrowid posrowid
sqlite3_fts5_create_function db negrowid negrowid

do_execsql_test 2.1 {
  INSERT INTO t1(rowid, a) VALUES(1001, 'x y 1');
  INSERT INTO t1(rowid, a) VALUES(1002, 'x y 2');
  INSERT INTO t1(rowid, a) VALUES(1003, 'x y 3');
  BEGIN;
    INSERT INTO t1(t1, rank) VALUES('rank', 'posrowid()');
    SELECT a FROM t1('x') ORDER BY rank;
} {{x y 1} {x y 2} {x y 3}}

do_execsql_test 2.2 {
  SAVEPOINT abc;
    INSERT INTO t1(t1, rank) VALUES('rank', 'negrowid()');
    SELECT a FROM t1('x') ORDER BY rank;
} {{x y 3} {x y 2} {x y 1}}

do_execsql_test 2.3 {
  ROLLBACK TO abc;
    SELECT a FROM t1('x') ORDER BY rank;
  COMMIT;
} {{x y 1} {x y 2} {x y 3}}

#-------------------------------------------------------------------------
# Test that the in-memory structure does not become inconsistent with
# respect to the on-disk configuration if a savepoint is rolled back.
#
do_execsql_test 3.1 {
  CREATE VIRTUAL TABLE t2 USING fts5(x, detail=%DETAIL%);
  INSERT INTO t2 VALUES('a 1');
  INSERT INTO t2 VALUES('a 2');
  INSERT INTO t2 VALUES('a 3');
  SELECT count(*) FROM t2_data;
} {5}

do_execsql_test 3.2 {
  BEGIN;
    SAVEPOINT one;
      INSERT INTO t2(rowid, x) VALUES(8, 'a 8');
      INSERT INTO t2(rowid, x) VALUES(7, 'a 7');
      INSERT INTO t2(rowid, x) VALUES(6, 'a 6');
      SELECT count(*) FROM t2_data;
} {7}
do_execsql_test 3.3 { INSERT INTO t2(t2) VALUES('integrity-check') } {}

do_execsql_test 3.4 {
  ROLLBACK TO one;
      SELECT count(*) FROM t2_data;
} {5}
do_execsql_test 3.5 { INSERT INTO t2(t2) VALUES('integrity-check') } {}

} ;# foreach_detail_mode

finish_test