SQLite

#include "fts3.h"
#ifndef SQLITE_CORE 
# include "sqlite3ext.h"
  SQLITE_EXTENSION_INIT1
#endif

static char *fts3EvalPhrasePoslist(Fts3Phrase *, int *);
static sqlite3_int64 fts3EvalPhraseDocid(Fts3Phrase *);

/* 
** Write a 64-bit variable-length integer to memory starting at p[0].
** The length of data written will be between 1 and FTS3_VARINT_MAX bytes.
** The number of bytes written is returned.
*/
int sqlite3Fts3PutVarint(char *p, sqlite_int64 v){
  unsigned char *q = (unsigned char *) p;

  } 

  /* Regardless of the strategy selected, FTS can deliver rows in rowid (or
  ** docid) order. Both ascending and descending are possible. 
  */
  if( pInfo->nOrderBy==1 ){
    struct sqlite3_index_orderby *pOrder = &pInfo->aOrderBy[0];
    if( pOrder->desc==0 
     && (pOrder->iColumn<0 || pOrder->iColumn==p->nColumn+1) 
    ){
      if( pOrder->desc ){
        pInfo->idxStr = "DESC";
      }else{
        pInfo->idxStr = "ASC";
      }

      pInfo->orderByConsumed = 1;
    }
  }

  return SQLITE_OK;
}

/*
** Implementation of xOpen method.

  sqlite3Fts3FreeDeferredTokens(pCsr);
  sqlite3_free(pCsr->aDoclist);
  sqlite3_free(pCsr->aMatchinfo);
  sqlite3_free(pCsr);
  return SQLITE_OK;
}

static int fts3RowidMethod(sqlite3_vtab_cursor *, sqlite3_int64*);

/*
** Position the pCsr->pStmt statement so that it is on the row
** of the %_content table that contains the last match.  Return
** SQLITE_OK on success.  
*/
static int fts3CursorSeek(sqlite3_context *pContext, Fts3Cursor *pCsr){
  if( pCsr->isRequireSeek ){

    sqlite3_bind_int64(pCsr->pStmt, 1, pCsr->iPrevId);
    pCsr->isRequireSeek = 0;
    if( SQLITE_ROW==sqlite3_step(pCsr->pStmt) ){
      return SQLITE_OK;
    }else{
      int rc = sqlite3_reset(pCsr->pStmt);
      if( rc==SQLITE_OK ){
        /* If no row was found and no error has occured, then the %_content
        ** table is missing a row that is present in the full-text index.

  return SQLITE_OK;
}

/*
** Append SegReader object pNew to the end of the pCsr->apSegment[] array.
*/
static int fts3SegReaderCursorAppend(
  Fts3MultiSegReader *pCsr, 
  Fts3SegReader *pNew
){
  if( (pCsr->nSegment%16)==0 ){
    Fts3SegReader **apNew;
    int nByte = (pCsr->nSegment + 16)*sizeof(Fts3SegReader*);
    apNew = (Fts3SegReader **)sqlite3_realloc(pCsr->apSegment, nByte);
    if( !apNew ){

  Fts3Table *p,                   /* FTS3 table handle */
  int iIndex,                     /* Index to search (from 0 to p->nIndex-1) */
  int iLevel,                     /* Level of segments to scan */
  const char *zTerm,              /* Term to query for */
  int nTerm,                      /* Size of zTerm in bytes */
  int isPrefix,                   /* True for a prefix search */
  int isScan,                     /* True to scan from zTerm to EOF */
  Fts3MultiSegReader *pCsr       /* Cursor object to populate */
){
  int rc = SQLITE_OK;
  int rc2;
  sqlite3_stmt *pStmt = 0;

  /* If iLevel is less than 0 and this is not a scan, include a seg-reader 
  ** for the pending-terms. If this is a scan, then this call must be being

  Fts3Table *p,                   /* FTS3 table handle */
  int iIndex,                     /* Index to search (from 0 to p->nIndex-1) */
  int iLevel,                     /* Level of segments to scan */
  const char *zTerm,              /* Term to query for */
  int nTerm,                      /* Size of zTerm in bytes */
  int isPrefix,                   /* True for a prefix search */
  int isScan,                     /* True to scan from zTerm to EOF */
  Fts3MultiSegReader *pCsr       /* Cursor object to populate */
){
  assert( iIndex>=0 && iIndex<p->nIndex );
  assert( iLevel==FTS3_SEGCURSOR_ALL
      ||  iLevel==FTS3_SEGCURSOR_PENDING 
      ||  iLevel>=0
  );
  assert( iLevel<FTS3_SEGDIR_MAXLEVEL );
  assert( FTS3_SEGCURSOR_ALL<0 && FTS3_SEGCURSOR_PENDING<0 );
  assert( isPrefix==0 || isScan==0 );

  /* "isScan" is only set to true by the ft4aux module, an ordinary
  ** full-text tables. */
  assert( isScan==0 || p->aIndex==0 );

  memset(pCsr, 0, sizeof(Fts3MultiSegReader));

  return fts3SegReaderCursor(
      p, iIndex, iLevel, zTerm, nTerm, isPrefix, isScan, pCsr
  );
}

static int fts3SegReaderCursorAddZero(
  Fts3Table *p,
  const char *zTerm,
  int nTerm,
  Fts3MultiSegReader *pCsr
){
  return fts3SegReaderCursor(p, 0, FTS3_SEGCURSOR_ALL, zTerm, nTerm, 0, 0,pCsr);
}


int sqlite3Fts3TermSegReaderCursor(
  Fts3Cursor *pCsr,               /* Virtual table cursor handle */
  const char *zTerm,              /* Term to query for */
  int nTerm,                      /* Size of zTerm in bytes */
  int isPrefix,                   /* True for a prefix search */
  Fts3MultiSegReader **ppSegcsr   /* OUT: Allocated seg-reader cursor */
){
  Fts3MultiSegReader *pSegcsr;   /* Object to allocate and return */
  int rc = SQLITE_NOMEM;          /* Return code */

  pSegcsr = sqlite3_malloc(sizeof(Fts3MultiSegReader));
  if( pSegcsr ){
    int i;
    int nCost = 0;
    int bFound = 0;               /* True once an index has been found */
    Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;

    if( isPrefix ){
      for(i=1; bFound==0 && i<p->nIndex; i++){
        if( p->aIndex[i].nPrefix==nTerm ){
          bFound = 1;
          rc = sqlite3Fts3SegReaderCursor(
              p, i, FTS3_SEGCURSOR_ALL, zTerm, nTerm, 0, 0, pSegcsr);
          pSegcsr->bLookup = 1;
        }
      }

      for(i=1; bFound==0 && i<p->nIndex; i++){
        if( p->aIndex[i].nPrefix==nTerm+1 ){
          bFound = 1;
          rc = sqlite3Fts3SegReaderCursor(
              p, i, FTS3_SEGCURSOR_ALL, zTerm, nTerm, 1, 0, pSegcsr
          );
          if( rc==SQLITE_OK ){
            rc = fts3SegReaderCursorAddZero(p, zTerm, nTerm, pSegcsr);
          }
        }
      }
    }

    if( bFound==0 ){
      rc = sqlite3Fts3SegReaderCursor(
          p, 0, FTS3_SEGCURSOR_ALL, zTerm, nTerm, isPrefix, 0, pSegcsr
      );
      pSegcsr->bLookup = !isPrefix;
    }
    for(i=0; rc==SQLITE_OK && i<pSegcsr->nSegment; i++){
      rc = sqlite3Fts3SegReaderCost(pCsr, pSegcsr->apSegment[i], &nCost);
    }
    pSegcsr->nCost = nCost;
  }

  *ppSegcsr = pSegcsr;
  return rc;
}

static void fts3SegReaderCursorFree(Fts3MultiSegReader *pSegcsr){
  sqlite3Fts3SegReaderFinish(pSegcsr);
  sqlite3_free(pSegcsr);
}

/*
** This function retreives the doclist for the specified term (or term
** prefix) from the database. 

  Fts3PhraseToken *pTok,          /* Token to query for */
  int iColumn,                    /* Column to query (or -ve for all columns) */
  int isReqPos,                   /* True to include position lists in output */
  int *pnOut,                     /* OUT: Size of buffer at *ppOut */
  char **ppOut                    /* OUT: Malloced result buffer */
){
  int rc;                         /* Return code */
  Fts3MultiSegReader *pSegcsr;   /* Seg-reader cursor for this term */
  TermSelect tsc;                 /* Context object for fts3TermSelectCb() */
  Fts3SegFilter filter;           /* Segment term filter configuration */

  pSegcsr = pTok->pSegcsr;
  memset(&tsc, 0, sizeof(TermSelect));
  tsc.isReqPos = isReqPos;

      pOut += sqlite3Fts3PutVarint(pOut, delta);
    }

    *pnList = (int)(pOut - aList);
  }
}

/*
** Return a DocList corresponding to the phrase *pPhrase.
**
** If this function returns SQLITE_OK, but *pnOut is set to a negative value,
** then no tokens in the phrase were looked up in the full-text index. This
** is only possible when this function is called from within xFilter(). The
** caller should assume that all documents match the phrase. The actual
** filtering will take place in xNext().

  int isTermPos = (pPhrase->nToken>1 || isReqPos);
  Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;
  int isFirst = 1;

  int iPrevTok = 0;
  int nDoc = 0;





















  for(ii=0; ii<pPhrase->nToken; ii++){
    Fts3PhraseToken *pTok;        /* Token to find doclist for */
    int iTok = 0;                 /* The token being queried this iteration */
    char *pList = 0;              /* Pointer to token doclist */
    int nList = 0;                /* Size of buffer at pList */

    /* Select a token to process. If this is an xFilter() call, then tokens 

      pTok = &pPhrase->aToken[iTok];
    }else{
      int nMinCost = 0x7FFFFFFF;
      int jj;

      /* Find the remaining token with the lowest cost. */
      for(jj=0; jj<pPhrase->nToken; jj++){
        Fts3MultiSegReader *pSegcsr = pPhrase->aToken[jj].pSegcsr;
        if( pSegcsr && pSegcsr->nCost<nMinCost ){
          iTok = jj;
          nMinCost = pSegcsr->nCost;
        }
      }
      pTok = &pPhrase->aToken[iTok];

  assert( pCsr->eEvalmode==FTS3_EVAL_FILTER );
  if( pnExpr && pExpr->eType!=FTSQUERY_AND ){
    (*pnExpr)++;
    pnExpr = 0;
  }

  if( pExpr->eType==FTSQUERY_PHRASE ){
    int ii;                       /* Used to iterate through phrase tokens */
    Fts3Phrase *pPhrase = pExpr->pPhrase;


    for(ii=0; rc==SQLITE_OK && ii<pPhrase->nToken; ii++){
      Fts3PhraseToken *pTok = &pPhrase->aToken[ii];
      if( pTok->pSegcsr==0 ){
        rc = sqlite3Fts3TermSegReaderCursor(
            pCsr, pTok->z, pTok->n, pTok->isPrefix, &pTok->pSegcsr
        );
      }
    }
  }else{ 
    rc = fts3ExprAllocateSegReaders(pCsr, pExpr->pLeft, pnExpr);
    if( rc==SQLITE_OK ){

static int fts3ExprCost(Fts3Expr *pExpr){
  int nCost;                      /* Return value */
  if( pExpr->eType==FTSQUERY_PHRASE ){
    Fts3Phrase *pPhrase = pExpr->pPhrase;
    int ii;
    nCost = 0;
    for(ii=0; ii<pPhrase->nToken; ii++){
      Fts3MultiSegReader *pSegcsr = pPhrase->aToken[ii].pSegcsr;
      if( pSegcsr ) nCost += pSegcsr->nCost;
    }
  }else{
    nCost = fts3ExprCost(pExpr->pLeft) + fts3ExprCost(pExpr->pRight);
  }
  return nCost;
}

** subsequently to determine whether or not an EOF was hit.
*/
static int fts3NextMethod(sqlite3_vtab_cursor *pCursor){
  int res;
  int rc = SQLITE_OK;             /* Return code */
  Fts3Cursor *pCsr = (Fts3Cursor *)pCursor;

  if( pCsr->bIncremental ){
    rc = sqlite3Fts3EvalNext(pCsr, pCsr->pExpr);
  }else{
    pCsr->eEvalmode = FTS3_EVAL_NEXT;
    do {
      if( pCsr->aDoclist==0 ){
        if( SQLITE_ROW!=sqlite3_step(pCsr->pStmt) ){
          pCsr->isEof = 1;
          rc = sqlite3_reset(pCsr->pStmt);
          break;
        }
        pCsr->iPrevId = sqlite3_column_int64(pCsr->pStmt, 0);
      }else{
        if( pCsr->desc==0 ){
          if( pCsr->pNextId>=&pCsr->aDoclist[pCsr->nDoclist] ){
            pCsr->isEof = 1;
            break;
          }
          fts3GetDeltaVarint(&pCsr->pNextId, &pCsr->iPrevId);
        }else{
          fts3GetReverseDeltaVarint(&pCsr->pNextId,pCsr->aDoclist,&pCsr->iPrevId);
          if( pCsr->pNextId<=pCsr->aDoclist ){
            pCsr->isEof = 1;
            break;
          }
        }
        sqlite3_reset(pCsr->pStmt);
        pCsr->isRequireSeek = 1;
        pCsr->isMatchinfoNeeded = 1;
      }
    }while( SQLITE_OK==(rc = fts3EvalDeferred(pCsr, &res)) && res==0 );
  }

  return rc;
}

/*
** This is the xFilter interface for the virtual table.  See
** the virtual table xFilter method documentation for additional

static int fts3FilterMethod(
  sqlite3_vtab_cursor *pCursor,   /* The cursor used for this query */
  int idxNum,                     /* Strategy index */
  const char *idxStr,             /* Unused */
  int nVal,                       /* Number of elements in apVal */
  sqlite3_value **apVal           /* Arguments for the indexing scheme */
){




  int rc;
  char *zSql;                     /* SQL statement used to access %_content */
  Fts3Table *p = (Fts3Table *)pCursor->pVtab;
  Fts3Cursor *pCsr = (Fts3Cursor *)pCursor;

  UNUSED_PARAMETER(idxStr);
  UNUSED_PARAMETER(nVal);

    }

    rc = sqlite3Fts3ExprParse(p->pTokenizer, p->azColumn, p->nColumn, 
        iCol, zQuery, -1, &pCsr->pExpr
    );
    if( rc!=SQLITE_OK ){
      if( rc==SQLITE_ERROR ){
        static const char *zErr = "malformed MATCH expression: [%s]";
        p->base.zErrMsg = sqlite3_mprintf(zErr, zQuery);

      }
      return rc;
    }

    rc = sqlite3Fts3ReadLock(p);
    if( rc!=SQLITE_OK ) return rc;

    pCsr->bIncremental = 1;
    rc = sqlite3Fts3EvalStart(pCsr, pCsr->pExpr, 1);

    sqlite3Fts3SegmentsClose(p);
    if( rc!=SQLITE_OK ) return rc;
    pCsr->pNextId = pCsr->aDoclist;
    pCsr->iPrevId = 0;
  }

  /* Compile a SELECT statement for this cursor. For a full-table-scan, the
  ** statement loops through all rows of the %_content table. For a
  ** full-text query or docid lookup, the statement retrieves a single
  ** row by docid.
  */
  if( idxNum==FTS3_FULLSCAN_SEARCH ){
    const char *zSort = (idxStr ? idxStr : "ASC");
    const char *zTmpl = "SELECT %s FROM %Q.'%q_content' AS x ORDER BY docid %s";
    zSql = sqlite3_mprintf(zTmpl, p->zReadExprlist, p->zDb, p->zName, zSort);
  }else{
    const char *zTmpl = "SELECT %s FROM %Q.'%q_content' AS x WHERE docid = ?";
    zSql = sqlite3_mprintf(zTmpl, p->zReadExprlist, p->zDb, p->zName);

  }
  if( !zSql ) return SQLITE_NOMEM;


  rc = sqlite3_prepare_v2(p->db, zSql, -1, &pCsr->pStmt, 0);
  sqlite3_free(zSql);
  if( rc!=SQLITE_OK ) return rc;

  if( idxNum==FTS3_DOCID_SEARCH ){
    rc = sqlite3_bind_value(pCsr->pStmt, 1, apVal[0]);
    if( rc!=SQLITE_OK ) return rc;
  }


  assert( pCsr->desc==0 );

  pCsr->eSearch = (i16)idxNum;
  if( rc==SQLITE_OK && pCsr->nDoclist>0 && idxStr && idxStr[0]=='D' ){
    sqlite3_int64 iDocid = 0;
    char *csr = pCsr->aDoclist;
    while( csr<&pCsr->aDoclist[pCsr->nDoclist] ){
      fts3GetDeltaVarint(&csr, &iDocid);
    }
    pCsr->pNextId = csr;

** This is the xRowid method. The SQLite core calls this routine to
** retrieve the rowid for the current row of the result set. fts3
** exposes %_content.docid as the rowid for the virtual table. The
** rowid should be written to *pRowid.
*/
static int fts3RowidMethod(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
  Fts3Cursor *pCsr = (Fts3Cursor *) pCursor;
  if( pCsr->bIncremental ){
    *pRowid = sqlite3Fts3EvalDocid(pCsr, pCsr->pExpr);
  }else if( pCsr->aDoclist ){
    *pRowid = pCsr->iPrevId;
  }else{
    /* This branch runs if the query is implemented using a full-table scan
    ** (not using the full-text index). In this case grab the rowid from the
    ** SELECT statement.
    */
    assert( pCsr->isRequireSeek==0 );

/*
** Load the doclist associated with expression pExpr to pExpr->aDoclist.
** The loaded doclist contains positions as well as the document ids.
** This is used by the matchinfo(), snippet() and offsets() auxillary
** functions.
*/
int sqlite3Fts3ExprLoadDoclist(Fts3Cursor *pCsr, Fts3Expr *pExpr){
  int rc = SQLITE_OK;
  if( pCsr->bIncremental==0 ){
    Fts3Phrase *pPhrase = pExpr->pPhrase;
    assert( pExpr->eType==FTSQUERY_PHRASE && pPhrase );
    assert( pCsr->eEvalmode==FTS3_EVAL_NEXT );
    rc = fts3EvalExpr(pCsr, pExpr, &pPhrase->aDoclist, &pPhrase->nDoclist, 1);
  }
  return rc;
}

/*
** TODO: This is something to do with matchinfo(). Similar to
** sqlite3ExprLoadDoclists() but slightly different.
**
** UPDATE: Only used when there are deferred tokens.
*/
int sqlite3Fts3ExprLoadFtDoclist(
  Fts3Cursor *pCsr, 
  Fts3Expr *pExpr,
  char **paDoclist,
  int *pnDoclist
){
  int rc = SQLITE_OK;
  assert( pExpr->eType==FTSQUERY_PHRASE && pExpr->pPhrase );
  assert( pCsr->eEvalmode==FTS3_EVAL_NEXT );
  assert( pCsr->bIncremental==0 );
  pCsr->eEvalmode = FTS3_EVAL_MATCHINFO;
  rc = fts3EvalExpr(pCsr, pExpr, paDoclist, pnDoclist, 1);
  pCsr->eEvalmode = FTS3_EVAL_NEXT;
  return rc;
}

    c = *p--; 
  }
  if( p>pStart ){ p = &p[2]; }
  while( *p++&0x80 );
  *ppPoslist = p;
}













































































/*
** Helper function used by the implementation of the overloaded snippet(),
** offsets() and optimize() SQL functions.
**
** If the value passed as the third argument is a blob of size
** sizeof(Fts3Cursor*), then the blob contents are copied to the 
** output variable *ppCsr and SQLITE_OK is returned. Otherwise, an error

  char **pzErrMsg,
  const sqlite3_api_routines *pApi
){
  SQLITE_EXTENSION_INIT2(pApi)
  return sqlite3Fts3Init(db);
}
#endif

/*************************************************************************
**************************************************************************
**************************************************************************
**************************************************************************
*************************************************************************/


/*
** Allocate an Fts3MultiSegReader for each token in the expression headed
** by pExpr. 
**
** An Fts3SegReader object is a cursor that can seek or scan a range of
** entries within a single segment b-tree. An Fts3MultiSegReader uses multiple
** Fts3SegReader objects internally to provide an interface to seek or scan
** within the union of all segments of a b-tree. Hence the name.
**
** If the allocated Fts3MultiSegReader just seeks to a single entry in a
** segment b-tree (if the term is not a prefix or it is a prefix for which
** there exists prefix b-tree of the right length) then it may be traversed
** and merged incrementally. Otherwise, it has to be merged into an in-memory 
** doclist and then traversed.
*/
static void fts3EvalAllocateReaders(
  Fts3Cursor *pCsr, 
  Fts3Expr *pExpr, 
  int *pnToken,                   /* OUT: Total number of tokens in phrase. */
  int *pRc
){
  if( pExpr && SQLITE_OK==*pRc ){
    if( pExpr->eType==FTSQUERY_PHRASE ){
      int i;
      int nToken = pExpr->pPhrase->nToken;
      *pnToken += nToken;
      for(i=0; i<nToken; i++){
        Fts3PhraseToken *pToken = &pExpr->pPhrase->aToken[i];
        int rc = sqlite3Fts3TermSegReaderCursor(pCsr, 
            pToken->z, pToken->n, pToken->isPrefix, &pToken->pSegcsr
        );
        if( rc!=SQLITE_OK ){
          *pRc = rc;
          return;
        }
      }
    }else{
      fts3EvalAllocateReaders(pCsr, pExpr->pLeft, pnToken, pRc);
      fts3EvalAllocateReaders(pCsr, pExpr->pRight, pnToken, pRc);
    }
  }
}

static int fts3EvalPhraseLoad(
  Fts3Cursor *pCsr, 
  Fts3Phrase *p
){
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
  int iToken;
  int rc = SQLITE_OK;

  char *aDoclist = 0;
  int nDoclist = 0;
  int iPrev = -1;

  for(iToken=0; rc==SQLITE_OK && iToken<p->nToken; iToken++){
    Fts3PhraseToken *pToken = &p->aToken[iToken];
    assert( pToken->pSegcsr || pToken->pDeferred );

    if( pToken->pDeferred==0 ){
      int nThis = 0;
      char *pThis = 0;
      rc = fts3TermSelect(pTab, pToken, p->iColumn, 1, &nThis, &pThis);
      if( rc==SQLITE_OK ){
        if( pThis==0 ){
          sqlite3_free(aDoclist);
          aDoclist = 0;
          nDoclist = 0;
          break;
        }else if( aDoclist==0 ){
          aDoclist = pThis;
          nDoclist = nThis;
        }else{
          assert( iPrev>=0 );
          fts3DoclistMerge(MERGE_POS_PHRASE, iToken-iPrev, 
              0, pThis, &nThis, aDoclist, nDoclist, pThis, nThis, 0
          );
          sqlite3_free(aDoclist);
          aDoclist = pThis;
          nDoclist = nThis;
        }
        iPrev = iToken;
      }
    }
  }

  if( rc==SQLITE_OK ){
    p->doclist.aAll = aDoclist;
    p->doclist.nAll = nDoclist;
  }else{
    sqlite3_free(aDoclist);
  }
  return rc;
}

static int fts3EvalDeferredPhrase(Fts3Cursor *pCsr, Fts3Phrase *pPhrase){
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
  int iToken;
  int rc = SQLITE_OK;

  int nMaxUndeferred = -1;
  char *aPoslist = 0;
  int nPoslist = 0;
  int iPrev = -1;

  for(iToken=0; rc==SQLITE_OK && iToken<pPhrase->nToken; iToken++){
    Fts3PhraseToken *pToken = &pPhrase->aToken[iToken];
    Fts3DeferredToken *pDeferred = pToken->pDeferred;

    if( pDeferred ){
      char *pList;
      int nList;
      rc = sqlite3Fts3DeferredTokenList(pDeferred, &pList, &nList);
      if( rc!=SQLITE_OK ) return rc;

      if( pList==0 ){
        sqlite3_free(aPoslist);
        pPhrase->doclist.pList = 0;
        pPhrase->doclist.nList = 0;
        return SQLITE_OK;

      }else if( aPoslist==0 ){
        aPoslist = pList;
        nPoslist = nList;

      }else{
        assert( iPrev>=0 );

        char *aOut = pList;
        char *p1 = aPoslist;
        char *p2 = aOut;

        fts3PoslistPhraseMerge(&aOut, iToken-iPrev, 0, 1, &p1, &p2);
        sqlite3_free(aPoslist);
        aPoslist = pList;
        nPoslist = aOut - aPoslist;
        if( nPoslist==0 ){
          sqlite3_free(aPoslist);
          pPhrase->doclist.pList = 0;
          pPhrase->doclist.nList = 0;
          return SQLITE_OK;
        }
      }
      iPrev = iToken;
    }else{
      nMaxUndeferred = iToken;
    }
  }

  if( iPrev>=0 ){
    if( nMaxUndeferred<0 ){
      pPhrase->doclist.pList = aPoslist;
      pPhrase->doclist.nList = nPoslist;
      pPhrase->doclist.iDocid = pCsr->iPrevId;
    }else{
      int nDistance;
      char *p1;
      char *p2;
      char *aOut;

      if( nMaxUndeferred>iPrev ){
        p1 = aPoslist;
        p2 = pPhrase->doclist.pList;
        nDistance = nMaxUndeferred - iPrev;
      }else{
        p1 = pPhrase->doclist.pList;
        p2 = aPoslist;
        nDistance = iPrev - nMaxUndeferred;
      }

      aOut = (char *)sqlite3_malloc(nPoslist+8);
      if( !aOut ){
        sqlite3_free(aPoslist);
        return SQLITE_NOMEM;
      }
      
      pPhrase->doclist.pList = aOut;
      if( fts3PoslistPhraseMerge(&aOut, nDistance, 0, 1, &p1, &p2) ){
        pPhrase->doclist.nList = (aOut - pPhrase->doclist.pList);
        sqlite3_free(aPoslist);
      }else{
        sqlite3_free(aOut);
        pPhrase->doclist.pList = 0;
        pPhrase->doclist.nList = 0;
      }
    }
  }

  return SQLITE_OK;
}


/*
** The following three functions:
**
**     fts3EvalPhraseStart()
**     fts3EvalPhraseNext()
**     fts3EvalPhraseReset()
**
** May be used with a phrase object after fts3EvalAllocateReaders() has been
** called to iterate through the set of docids that match the phrase.
**
** After a successful call to fts3EvalPhraseNext(), the following two 
** functions may be called to access the current docid and position-list.
**
**     fts3EvalPhraseDocid()
**     fts3EvalPhrasePoslist()
*/
static int fts3EvalPhraseStart(Fts3Cursor *pCsr, int bOptOk, Fts3Phrase *p){
  int rc;
  Fts3Doclist *pList = &p->doclist;
  Fts3PhraseToken *pFirst = &p->aToken[0];

  assert( pList->aAll==0 );

  if( p->nToken==1 && bOptOk==1 
   && pFirst->pSegcsr && pFirst->pSegcsr->bLookup 
  ){
    /* Use the incremental approach. */
    Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
    int iCol = (p->iColumn >= pTab->nColumn ? -1 : p->iColumn);
    rc = sqlite3Fts3MsrIncrStart(
        pTab, pFirst->pSegcsr, iCol, pFirst->z, pFirst->n);
    p->bIncr = 1;

  }else{

    /* Load the full doclist for the phrase into memory. */
    rc = fts3EvalPhraseLoad(pCsr, p);
    p->bIncr = 0;
  }

  assert( rc!=SQLITE_OK || p->nToken<1 || p->aToken[0].pSegcsr==0 || p->bIncr );
  return rc;
}

/*
** Attempt to move the phrase iterator to point to the next matching docid. 
** If an error occurs, return an SQLite error code. Otherwise, return 
** SQLITE_OK.
**
** If there is no "next" entry and no error occurs, then *pbEof is set to
** 1 before returning. Otherwise, if no error occurs and the iterator is
** successfully advanced, *pbEof is set to 0.
*/
static int fts3EvalPhraseNext(Fts3Cursor *pCsr, Fts3Phrase *p, u8 *pbEof){
  int rc = SQLITE_OK;

  if( p->bIncr ){
    Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
    assert( p->nToken==1 );
    rc = sqlite3Fts3MsrIncrNext(pTab, p->aToken[0].pSegcsr, 
        &p->doclist.iDocid, &p->doclist.pList, &p->doclist.nList
    );
    if( rc==SQLITE_OK && !p->doclist.pList ){
      *pbEof = 1;
    }
  }else{
    char *pIter;
    Fts3Doclist *pDL = &p->doclist;

    if( pDL->pNextDocid ){
      pIter = pDL->pNextDocid;
    }else{
      pIter = pDL->aAll;
    }

    if( pIter>=&pDL->aAll[pDL->nAll] ){
      /* We have already reached the end of this doclist. EOF. */
      *pbEof = 1;
    }else{
      fts3GetDeltaVarint(&pIter, &pDL->iDocid);
      pDL->pList = pIter;
      fts3PoslistCopy(0, &pIter);
      pDL->nList = (pIter - pDL->pList);
      pDL->pNextDocid = pIter;
      *pbEof = 0;
    }
  }

  return rc;
}

static int fts3EvalPhraseReset(Fts3Cursor *pCsr, Fts3Phrase *p){
  return SQLITE_OK;
}

static sqlite3_int64 fts3EvalPhraseDocid(Fts3Phrase *p){
  return p->doclist.iDocid;
}

static char *fts3EvalPhrasePoslist(Fts3Phrase *p, int *pnList){
  if( pnList ){
    *pnList = p->doclist.nList;
  }
  return p->doclist.pList;
}

static void fts3EvalStartReaders(
  Fts3Cursor *pCsr, 
  Fts3Expr *pExpr, 
  int bOptOk,
  int *pRc
){
  if( pExpr && SQLITE_OK==*pRc ){
    if( pExpr->eType==FTSQUERY_PHRASE ){
      int i;
      int nToken = pExpr->pPhrase->nToken;
      for(i=0; i<nToken; i++){
        if( pExpr->pPhrase->aToken[i].pDeferred==0 ) break;
      }
      pExpr->bDeferred = (i==nToken);
      *pRc = fts3EvalPhraseStart(pCsr, bOptOk, pExpr->pPhrase);
    }else{
      if( pExpr->eType==FTSQUERY_NEAR ){
        bOptOk = 0;
      }
      fts3EvalStartReaders(pCsr, pExpr->pLeft, bOptOk, pRc);
      fts3EvalStartReaders(pCsr, pExpr->pRight, bOptOk, pRc);
      pExpr->bDeferred = (pExpr->pLeft->bDeferred && pExpr->pRight->bDeferred);
    }
  }
}

static void fts3EvalNearMerge(
  Fts3Expr *p1,
  Fts3Expr *p2,
  int nNear,
  int *pRc
){
  if( *pRc==SQLITE_OK ){
    int rc;                         /* Return code */
    Fts3Phrase *pLeft = p1->pPhrase;
    Fts3Phrase *pRight = p2->pPhrase;
  
    assert( p2->eType==FTSQUERY_PHRASE && pLeft );
    assert( p2->eType==FTSQUERY_PHRASE && pRight );
  
    if( pLeft->doclist.aAll==0 ){
      sqlite3_free(pRight->doclist.aAll);
      pRight->doclist.aAll = 0;
      pRight->doclist.nAll = 0;
    }else if( pRight->doclist.aAll ){
      char *aOut;                 /* Buffer in which to assemble new doclist */
      int nOut;                   /* Size of buffer aOut in bytes */
  
      *pRc = fts3NearMerge(MERGE_POS_NEAR, nNear, 
          pLeft->nToken, pLeft->doclist.aAll, pLeft->doclist.nAll,
          pRight->nToken, pRight->doclist.aAll, pRight->doclist.nAll,
          &aOut, &nOut
      );
      sqlite3_free(pRight->doclist.aAll);
      pRight->doclist.aAll = aOut;
      pRight->doclist.nAll = nOut;
    }
  }
}

static void fts3EvalNearTrim(Fts3Cursor *pCsr, Fts3Expr *pExpr, int *pRc){

  if( pExpr && SQLITE_OK==*pRc ){
    if( pExpr->eType==FTSQUERY_NEAR ){
      Fts3Expr *pLeft = pExpr->pLeft;
      int nPhrase = 2;
      Fts3Expr **aPhrase;

      assert( pLeft );
      assert( pExpr->pRight );
      assert( pExpr->pRight->eType==FTSQUERY_PHRASE );

      while( pLeft->eType!=FTSQUERY_PHRASE ){
        assert( pLeft->eType==FTSQUERY_NEAR );
        assert( pLeft->pRight->eType==FTSQUERY_PHRASE );
        pLeft = pLeft->pLeft;
        nPhrase++;
      }

      aPhrase = (Fts3Expr **)sqlite3_malloc(sizeof(Fts3Expr *) * nPhrase);
      if( !aPhrase ){
        *pRc = SQLITE_NOMEM;
      }else{
        int i = 1;
        aPhrase[0] = pLeft;
        do {
          pLeft = pLeft->pParent;
          aPhrase[i++] = pLeft->pRight;
        }while( pLeft!=pExpr );

        for(i=0; i<(nPhrase-1); i++){
          int nNear = aPhrase[i+1]->pParent->nNear;
          fts3EvalNearMerge(aPhrase[i], aPhrase[i+1], nNear, pRc);
        }
        for(i=nPhrase-2; i>=0; i--){
          int nNear = aPhrase[i+1]->pParent->nNear;
          fts3EvalNearMerge(aPhrase[i+1], aPhrase[i], nNear, pRc);
        }

        sqlite3_free(aPhrase);
      }

    }else{
      fts3EvalNearTrim(pCsr, pExpr->pLeft, pRc);
      fts3EvalNearTrim(pCsr, pExpr->pRight, pRc);
    }
  }
}

typedef struct Fts3TokenAndCost Fts3TokenAndCost;
struct Fts3TokenAndCost {
  Fts3PhraseToken *pToken;
  int nOvfl;
  int iCol;
};

static void fts3EvalTokenCosts(
  Fts3Cursor *pCsr, 
  Fts3Expr *pExpr, 
  Fts3TokenAndCost **ppTC,
  int *pRc
){
  if( *pRc==SQLITE_OK && pExpr ){
    if( pExpr->eType==FTSQUERY_PHRASE ){
      Fts3Phrase *pPhrase = pExpr->pPhrase;
      int i;
      for(i=0; *pRc==SQLITE_OK && i<pPhrase->nToken; i++){
        Fts3TokenAndCost *pTC = (*ppTC)++;
        pTC->pToken = &pPhrase->aToken[i];
        pTC->iCol = pPhrase->iColumn;
        *pRc = sqlite3Fts3MsrOvfl(pCsr, pTC->pToken->pSegcsr, &pTC->nOvfl);
      }
    }else if( pExpr->eType==FTSQUERY_AND ){
      fts3EvalTokenCosts(pCsr, pExpr->pLeft, ppTC, pRc);
      fts3EvalTokenCosts(pCsr, pExpr->pRight, ppTC, pRc);
    }
  }
}

static int fts3EvalAverageDocsize(Fts3Cursor *pCsr, int *pnPage){
  if( pCsr->nRowAvg==0 ){
    /* The average document size, which is required to calculate the cost
     ** of each doclist, has not yet been determined. Read the required 
     ** data from the %_stat table to calculate it.
     **
     ** Entry 0 of the %_stat table is a blob containing (nCol+1) FTS3 
     ** varints, where nCol is the number of columns in the FTS3 table.
     ** The first varint is the number of documents currently stored in
     ** the table. The following nCol varints contain the total amount of
     ** data stored in all rows of each column of the table, from left
     ** to right.
     */
    int rc;
    Fts3Table *p = (Fts3Table*)pCsr->base.pVtab;
    sqlite3_stmt *pStmt;
    sqlite3_int64 nDoc = 0;
    sqlite3_int64 nByte = 0;
    const char *pEnd;
    const char *a;

    rc = sqlite3Fts3SelectDoctotal(p, &pStmt);
    if( rc!=SQLITE_OK ) return rc;
    a = sqlite3_column_blob(pStmt, 0);
    assert( a );

    pEnd = &a[sqlite3_column_bytes(pStmt, 0)];
    a += sqlite3Fts3GetVarint(a, &nDoc);
    while( a<pEnd ){
      a += sqlite3Fts3GetVarint(a, &nByte);
    }
    if( nDoc==0 || nByte==0 ){
      sqlite3_reset(pStmt);
      return SQLITE_CORRUPT_VTAB;
    }

    pCsr->nRowAvg = (int)(((nByte / nDoc) + p->nPgsz) / p->nPgsz);
    assert( pCsr->nRowAvg>0 ); 
    rc = sqlite3_reset(pStmt);
    if( rc!=SQLITE_OK ) return rc;
  }

  *pnPage = pCsr->nRowAvg;
  return SQLITE_OK;
}

int sqlite3Fts3EvalStart(Fts3Cursor *pCsr, Fts3Expr *pExpr, int bOptOk){
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
  int rc = SQLITE_OK;
  int nToken = 0;

  /* Allocate a MultiSegReader for each token in the expression. */
  fts3EvalAllocateReaders(pCsr, pExpr, &nToken, &rc);

  /* Call fts3EvalPhraseStart() on all phrases in the expression. TODO:
  ** This call will eventually also be responsible for determining which
  ** tokens are 'deferred' until the document text is loaded into memory.
  **
  ** Each token in each phrase is dealt with using one of the following
  ** three strategies:
  **
  **   1. Entire doclist loaded into memory as part of the
  **      fts3EvalStartReaders() call.
  **
  **   2. Doclist loaded into memory incrementally, as part of each
  **      sqlite3Fts3EvalNext() call.
  **
  **   3. Token doclist is never loaded. Instead, documents are loaded into
  **      memory and scanned for the token as part of the sqlite3Fts3EvalNext()
  **      call. This is known as a "deferred" token.
  */

  /* If bOptOk is true, check if there are any tokens that can be 
  ** deferred (strategy 3). */
  if( rc==SQLITE_OK && bOptOk && nToken>1 && pTab->bHasStat ){
    Fts3TokenAndCost *aTC;
    aTC = (Fts3TokenAndCost *)sqlite3_malloc(sizeof(Fts3TokenAndCost) * nToken);
    if( !aTC ){
      rc = SQLITE_NOMEM;
    }else{
      int ii;
      int nDocEst = 0;
      int nDocSize;
      Fts3TokenAndCost *pTC = aTC;

      rc = fts3EvalAverageDocsize(pCsr, &nDocSize);
      fts3EvalTokenCosts(pCsr, pExpr, &pTC, &rc);
      nToken = pTC-aTC;

      for(ii=0; rc==SQLITE_OK && ii<nToken; ii++){
        int jj;
        pTC = 0;
        for(jj=0; jj<nToken; jj++){
          if( aTC[jj].pToken && (!pTC || aTC[jj].nOvfl<pTC->nOvfl) ){
            pTC = &aTC[jj];
          }
        }
        assert( pTC );

        /* At this point pTC points to the cheapest remaining token. */
        if( ii==0 ){
          if( pTC->nOvfl ){
            nDocEst = (pTC->nOvfl * pTab->nPgsz + pTab->nPgsz) / 10;
          }else{
            /* TODO: Fix this so that the doclist need not be read twice. */
            Fts3PhraseToken *pToken = pTC->pToken;
            int nList = 0;
            char *pList = 0;
            rc = fts3TermSelect(pTab, pToken, pTC->iCol, 1, &nList, &pList);
            if( rc==SQLITE_OK ){
              nDocEst = fts3DoclistCountDocids(1, pList, nList);
            }
            sqlite3_free(pList);
            if( rc==SQLITE_OK ){
              rc = sqlite3Fts3TermSegReaderCursor(pCsr, 
                pToken->z, pToken->n, pToken->isPrefix, &pToken->pSegcsr
              );
            }
          }
        }else{
          if( pTC->nOvfl>=(nDocEst*nDocSize) ){
            Fts3PhraseToken *pToken = pTC->pToken;
            rc = sqlite3Fts3DeferToken(pCsr, pToken, pTC->iCol);
            fts3SegReaderCursorFree(pToken->pSegcsr);
            pToken->pSegcsr = 0;
          }
          nDocEst = 1 + (nDocEst/4);
        }
        pTC->pToken = 0;
      }
      sqlite3_free(aTC);
    }
  }

  fts3EvalStartReaders(pCsr, pExpr, bOptOk, &rc);

  /* Fix the results of NEAR expressions. */
  fts3EvalNearTrim(pCsr, pExpr, &rc);

  return rc;
}

static void fts3EvalNext(
  Fts3Cursor *pCsr, 
  Fts3Expr *pExpr, 
  int *pRc
){
  if( *pRc==SQLITE_OK ){

    pExpr->bStart = 1;
    switch( pExpr->eType ){

      case FTSQUERY_NEAR:
      case FTSQUERY_AND: {
        Fts3Expr *pLeft = pExpr->pLeft;
        Fts3Expr *pRight = pExpr->pRight;

        assert( !pLeft->bDeferred || !pRight->bDeferred );
        if( pLeft->bDeferred ){
          fts3EvalNext(pCsr, pRight, pRc);
          pExpr->iDocid = pRight->iDocid;
          pExpr->bEof = pRight->bEof;
        }else if( pRight->bDeferred ){
          fts3EvalNext(pCsr, pLeft, pRc);
          pExpr->iDocid = pLeft->iDocid;
          pExpr->bEof = pLeft->bEof;
        }else{
          fts3EvalNext(pCsr, pLeft, pRc);
          fts3EvalNext(pCsr, pRight, pRc);

          while( !pLeft->bEof && !pRight->bEof && *pRc==SQLITE_OK ){
            int iDiff = pLeft->iDocid - pRight->iDocid;
            if( iDiff==0 ) break;
            if( iDiff<0 ){
              fts3EvalNext(pCsr, pLeft, pRc);
            }else{
              fts3EvalNext(pCsr, pRight, pRc);
            }
          }
    
          pExpr->iDocid = pLeft->iDocid;
          pExpr->bEof = (pLeft->bEof || pRight->bEof);
        }
        break;
      }
  
      case FTSQUERY_OR: {
        Fts3Expr *pLeft = pExpr->pLeft;
        Fts3Expr *pRight = pExpr->pRight;

        assert( pLeft->bStart || pLeft->iDocid==pRight->iDocid );
        assert( pRight->bStart || pLeft->iDocid==pRight->iDocid );

        if( pLeft->iDocid==pRight->iDocid ){
          fts3EvalNext(pCsr, pLeft, pRc);
          fts3EvalNext(pCsr, pRight, pRc);
        }else if( 
          pRight->bEof || (pLeft->bEof==0 && pLeft->iDocid<pRight->iDocid) 
        ){
          fts3EvalNext(pCsr, pLeft, pRc);
        }else{
          fts3EvalNext(pCsr, pRight, pRc);
        }
  
        pExpr->bEof = (pLeft->bEof && pRight->bEof);
        if( pRight->bEof || (pLeft->bEof==0 &&  pLeft->iDocid<pRight->iDocid) ){
          pExpr->iDocid = pLeft->iDocid;
        }else{
          pExpr->iDocid = pRight->iDocid;
        }

        break;
      }

      case FTSQUERY_NOT: {
        Fts3Expr *pLeft = pExpr->pLeft;
        Fts3Expr *pRight = pExpr->pRight;

        if( pRight->bStart==0 ){
          fts3EvalNext(pCsr, pRight, pRc);
          assert( *pRc!=SQLITE_OK || pRight->bStart );
        }
        do {
          fts3EvalNext(pCsr, pLeft, pRc);
          if( pLeft->bEof ) break;
          while( !*pRc && !pRight->bEof && pRight->iDocid<pLeft->iDocid ){
            fts3EvalNext(pCsr, pRight, pRc);
          }
        }while( !pRight->bEof && pRight->iDocid==pLeft->iDocid && !*pRc );
        pExpr->iDocid = pLeft->iDocid;
        pExpr->bEof = pLeft->bEof;
        break;
      }

      default:
        assert( pExpr->eType==FTSQUERY_PHRASE );
        *pRc = fts3EvalPhraseNext(pCsr, pExpr->pPhrase, &pExpr->bEof);
        pExpr->iDocid = fts3EvalPhraseDocid(pExpr->pPhrase);
        break;
    }
  }
}

static int fts3EvalDeferredTest(Fts3Cursor *pCsr, Fts3Expr *pExpr, int *pRc){
  int bHit = 0;
  if( *pRc==SQLITE_OK ){
    switch( pExpr->eType ){
      case FTSQUERY_NEAR:
      case FTSQUERY_AND:
        bHit = (
            fts3EvalDeferredTest(pCsr, pExpr->pLeft, pRc)
         && fts3EvalDeferredTest(pCsr, pExpr->pRight, pRc)
        );
        break;

      case FTSQUERY_OR:
        bHit = (
            fts3EvalDeferredTest(pCsr, pExpr->pLeft, pRc)
         || fts3EvalDeferredTest(pCsr, pExpr->pRight, pRc)
        );
        break;

      case FTSQUERY_NOT:
        bHit = (
            fts3EvalDeferredTest(pCsr, pExpr->pLeft, pRc)
         && !fts3EvalDeferredTest(pCsr, pExpr->pRight, pRc)
        );
        break;

      default:
        assert( pExpr->eType==FTSQUERY_PHRASE );
        *pRc = fts3EvalDeferredPhrase(pCsr, pExpr->pPhrase);
        bHit = (pExpr->pPhrase->doclist.pList!=0);
        pExpr->iDocid = pCsr->iPrevId;
        break;
    }
  }
  return bHit;
}

/*
** Return 1 if both of the following are true:
**
**   1. *pRc is SQLITE_OK when this function returns, and
**
**   2. After scanning the current FTS table row for the deferred tokens,
**      it is determined that the row does not match the query.
*/
static int fts3EvalLoadDeferred(Fts3Cursor *pCsr, int *pRc){
  int rc = *pRc;
  int bMiss = 0;
  if( rc==SQLITE_OK && pCsr->pDeferred ){
    rc = fts3CursorSeek(0, pCsr);
    if( rc==SQLITE_OK ){
      sqlite3Fts3FreeDeferredDoclists(pCsr);
      rc = sqlite3Fts3CacheDeferredDoclists(pCsr);
    }
    bMiss = (0==fts3EvalDeferredTest(pCsr, pCsr->pExpr, &rc));
    sqlite3Fts3FreeDeferredDoclists(pCsr);
    *pRc = rc;
  }
  return (rc==SQLITE_OK && bMiss);
}

/*
** Advance to the next document that matches the expression passed as an
** argument.
*/
int sqlite3Fts3EvalNext(Fts3Cursor *pCsr, Fts3Expr *pExpr){
  int rc = SQLITE_OK;             /* Return Code */
  assert( pCsr->isEof==0 );
  assert( pCsr->bIncremental );
  if( pExpr==0 ){
    pCsr->isEof = 1;
  }else{
    do {
      sqlite3_reset(pCsr->pStmt);
      fts3EvalNext(pCsr, pExpr, &rc);
      pCsr->isEof = pExpr->bEof;
      pCsr->isRequireSeek = 1;
      pCsr->isMatchinfoNeeded = 1;
      pCsr->iPrevId = pExpr->iDocid;
    }while( pCsr->isEof==0 && fts3EvalLoadDeferred(pCsr, &rc) );
  }
  return rc;
}

int sqlite3Fts3EvalFinish(Fts3Cursor *pCsr, Fts3Expr *pExpr){
  return SQLITE_OK;
}

sqlite3_int64 sqlite3Fts3EvalDocid(Fts3Cursor *pCsr, Fts3Expr *pExpr){
  return pExpr->iDocid;
}

/*
** Return a pointer to the entire doclist, including positions, associated 
** with the phrase passed as the second argument.
*/
int sqlite3Fts3EvalPhraseDoclist(
  Fts3Cursor *pCsr,               /* FTS3 cursor object */
  Fts3Expr *pExpr,                /* Phrase to return doclist for */
  const char **ppList,            /* OUT: Buffer containing doclist */
  int *pnList                     /* OUT: Size of returned buffer, in bytes */
){
  int rc = SQLITE_OK;
  Fts3Phrase *pPhrase = pExpr->pPhrase;

  if( pPhrase->bIncr ){
    /* This phrase was being loaded from disk incrementally. But the 
    ** matchinfo() function requires that the entire doclist be loaded into
    ** memory. This block loads the doclist into memory and modifies the
    ** Fts3Phrase structure so that it does not use the incremental strategy.
    */
    TESTONLY( int bEof = pExpr->bEof; )
    TESTONLY( int bStart = pExpr->bStart; )
    sqlite3_int64 iDocid = pExpr->iDocid;

    sqlite3Fts3EvalPhraseCleanup(pPhrase);
    pExpr->iDocid = 0;

    rc = sqlite3Fts3EvalStart(pCsr, pExpr, 0);
    assert( pExpr->bEof==bEof );
    assert( pExpr->bStart==bStart );
    assert( rc!=SQLITE_OK || pPhrase->bIncr==0 );
    if( pExpr->bStart && !pExpr->bEof ){
      pExpr->bStart = 0;
      while( rc==SQLITE_OK && pExpr->bEof==0 && pExpr->iDocid!=iDocid ){
        fts3EvalNext(pCsr, pExpr, &rc);
      }
    }
  }

  *pnList = pPhrase->doclist.nAll;
  *ppList = pPhrase->doclist.aAll;
  return rc;
}

char *sqlite3Fts3EvalPhrasePoslist(
  Fts3Cursor *pCsr,               /* FTS3 cursor object */
  Fts3Expr *pExpr,                /* Phrase to return doclist for */
  sqlite3_int64 iDocid,           /* Docid to return position list for */
  int iCol                        /* Column to return position list for */
){
  Fts3Phrase *pPhrase = pExpr->pPhrase;
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
  char *pIter = pPhrase->doclist.pList;
  int iThis;

  assert( iCol>=0 && iCol<pTab->nColumn );
  if( !pIter 
   || pExpr->bEof 
   || pExpr->iDocid!=iDocid
   || (pPhrase->iColumn<pTab->nColumn && pPhrase->iColumn!=iCol) 
  ){
    return 0;
  }

  assert( pPhrase->doclist.nList>0 );
  if( *pIter==0x01 ){
    pIter++;
    pIter += sqlite3Fts3GetVarint32(pIter, &iThis);
  }else{
    iThis = 0;
  }
  while( iThis<iCol ){
    fts3ColumnlistCopy(0, &pIter);
    if( *pIter==0x00 ) return 0;
    pIter++;
    pIter += sqlite3Fts3GetVarint32(pIter, &iThis);
  }

  return ((iCol==iThis)?pIter:0);
}

void sqlite3Fts3EvalPhraseCleanup(Fts3Phrase *pPhrase){
  int i;
  sqlite3_free(pPhrase->doclist.aAll);
  memset(&pPhrase->doclist, 0, sizeof(Fts3Doclist));
  for(i=0; i<pPhrase->nToken; i++){
    fts3SegReaderCursorFree(pPhrase->aToken[i].pSegcsr);
    pPhrase->aToken[i].pSegcsr = 0;
  }
}

#endif

/*
** Macro to return the number of elements in an array. SQLite has a
** similar macro called ArraySize(). Use a different name to avoid
** a collision when building an amalgamation with built-in FTS3.
*/
#define SizeofArray(X) ((int)(sizeof(X)/sizeof(X[0])))


#ifndef MIN
# define MIN(x,y) ((x)<(y)?(x):(y))
#endif

/*
** Maximum length of a varint encoded integer. The varint format is different
** from that used by SQLite, so the maximum length is 10, not 9.
*/
#define FTS3_VARINT_MAX 10

/*

typedef struct Fts3Table Fts3Table;
typedef struct Fts3Cursor Fts3Cursor;
typedef struct Fts3Expr Fts3Expr;
typedef struct Fts3Phrase Fts3Phrase;
typedef struct Fts3PhraseToken Fts3PhraseToken;

typedef struct Fts3Doclist Fts3Doclist;
typedef struct Fts3SegFilter Fts3SegFilter;
typedef struct Fts3DeferredToken Fts3DeferredToken;
typedef struct Fts3SegReader Fts3SegReader;
typedef struct Fts3MultiSegReader Fts3MultiSegReader;

/*
** A connection to a fulltext index is an instance of the following
** structure. The xCreate and xConnect methods create an instance
** of this structure and xDestroy and xDisconnect free that instance.
** All other methods receive a pointer to the structure as one of their
** arguments.

struct Fts3Cursor {
  sqlite3_vtab_cursor base;       /* Base class used by SQLite core */
  i16 eSearch;                    /* Search strategy (see below) */
  u8 isEof;                       /* True if at End Of Results */
  u8 isRequireSeek;               /* True if must seek pStmt to %_content row */
  sqlite3_stmt *pStmt;            /* Prepared statement in use by the cursor */
  Fts3Expr *pExpr;                /* Parsed MATCH query string */
  int bIncremental;               /* True to use incremental querying */
  int nPhrase;                    /* Number of matchable phrases in query */
  Fts3DeferredToken *pDeferred;   /* Deferred search tokens, if any */
  sqlite3_int64 iPrevId;          /* Previous id read from aDoclist */
  char *pNextId;                  /* Pointer into the body of aDoclist */
  char *aDoclist;                 /* List of docids for full-text queries */
  int nDoclist;                   /* Size of buffer at aDoclist */
  int desc;                       /* True to sort in descending order */

** indicating that all columns should be searched,
** then eSearch would be set to FTS3_FULLTEXT_SEARCH+4.
*/
#define FTS3_FULLSCAN_SEARCH 0    /* Linear scan of %_content table */
#define FTS3_DOCID_SEARCH    1    /* Lookup by rowid on %_content table */
#define FTS3_FULLTEXT_SEARCH 2    /* Full-text index search */


struct Fts3Doclist {
  char *aAll;                    /* Array containing doclist (or NULL) */
  int nAll;                      /* Size of a[] in bytes */

  sqlite3_int64 iDocid;          /* Current docid (if p!=0) */
  char *pNextDocid;              /* Pointer to next docid */
  char *pList;                   /* Pointer to position list following iDocid */
  int nList;                     /* Length of position list */
} doclist;

/*
** A "phrase" is a sequence of one or more tokens that must match in
** sequence.  A single token is the base case and the most common case.
** For a sequence of tokens contained in double-quotes (i.e. "one two three")
** nToken will be the number of tokens in the string.
*/
struct Fts3PhraseToken {
  char *z;                        /* Text of the token */
  int n;                          /* Number of bytes in buffer z */
  int isPrefix;                   /* True if token ends with a "*" character */

  /* Variables above this point are populated when the expression is
  ** parsed (by code in fts3_expr.c). Below this point the variables are
  ** used when evaluating the expression. */

  int bFulltext;                  /* True if full-text index was used */

  Fts3DeferredToken *pDeferred;   /* Deferred token object for this token */
  Fts3MultiSegReader *pSegcsr;    /* Segment-reader for this token */
};

struct Fts3Phrase {

  /* Cache of doclist for this phrase. */
  Fts3Doclist doclist;
  int bIncr;                 /* True if doclist is loaded incrementally */

#if 1
  int isLoaded;              /* True if aDoclist/nDoclist are initialized. */
  char *aDoclist;            /* Buffer containing doclist */
  int nDoclist;              /* Size of aDoclist in bytes */
  sqlite3_int64 iCurrent;
  char *pCurrent;
#endif

  /* Variables below this point are populated by fts3_expr.c when parsing 
  ** a MATCH expression. Everything above is part of the evaluation phase. 
  */
  int nToken;                /* Number of tokens in the phrase */
  int iColumn;               /* Index of column this phrase must match */
  Fts3PhraseToken aToken[1]; /* One entry for each token in the phrase */
};

/*
** A tree of these objects forms the RHS of a MATCH operator.
**
** If Fts3Expr.eType is FTSQUERY_PHRASE and isLoaded is true, then aDoclist 

struct Fts3Expr {
  int eType;                 /* One of the FTSQUERY_XXX values defined below */
  int nNear;                 /* Valid if eType==FTSQUERY_NEAR */
  Fts3Expr *pParent;         /* pParent->pLeft==this or pParent->pRight==this */
  Fts3Expr *pLeft;           /* Left operand */
  Fts3Expr *pRight;          /* Right operand */
  Fts3Phrase *pPhrase;       /* Valid if eType==FTSQUERY_PHRASE */

  /* The following are used by the fts3_eval.c module. */
  sqlite3_int64 iDocid;      /* Current docid */
  u8 bEof;                   /* True this expression is at EOF already */
  u8 bStart;                 /* True if iDocid is valid */
  u8 bDeferred;              /* True if this expression is entirely deferred */
};

/*
** Candidate values for Fts3Query.eType. Note that the order of the first
** four values is in order of precedence when parsing expressions. For 
** example, the following:
**

char *sqlite3Fts3DeferredDoclist(Fts3DeferredToken *, int *);
void sqlite3Fts3SegmentsClose(Fts3Table *);

/* Special values interpreted by sqlite3SegReaderCursor() */
#define FTS3_SEGCURSOR_PENDING        -1
#define FTS3_SEGCURSOR_ALL            -2

int sqlite3Fts3SegReaderStart(Fts3Table*, Fts3MultiSegReader*, Fts3SegFilter*);
int sqlite3Fts3SegReaderStep(Fts3Table *, Fts3MultiSegReader *);
void sqlite3Fts3SegReaderFinish(Fts3MultiSegReader *);

int sqlite3Fts3SegReaderCursor(
    Fts3Table *, int, int, const char *, int, int, int, Fts3MultiSegReader *);

/* Flags allowed as part of the 4th argument to SegmentReaderIterate() */
#define FTS3_SEGMENT_REQUIRE_POS   0x00000001
#define FTS3_SEGMENT_IGNORE_EMPTY  0x00000002
#define FTS3_SEGMENT_COLUMN_FILTER 0x00000004
#define FTS3_SEGMENT_PREFIX        0x00000008
#define FTS3_SEGMENT_SCAN          0x00000010

/* Type passed as 4th argument to SegmentReaderIterate() */
struct Fts3SegFilter {
  const char *zTerm;
  int nTerm;
  int iCol;
  int flags;
};

struct Fts3MultiSegReader {
  /* Used internally by sqlite3Fts3SegReaderXXX() calls */
  Fts3SegReader **apSegment;      /* Array of Fts3SegReader objects */
  int nSegment;                   /* Size of apSegment array */
  int nAdvance;                   /* How many seg-readers to advance */
  Fts3SegFilter *pFilter;         /* Pointer to filter object */
  char *aBuffer;                  /* Buffer to merge doclists in */
  int nBuffer;                    /* Allocated size of aBuffer[] in bytes */

  int iColFilter;                 /* If >=0, filter for this column */

  /* Used by fts3.c only. */
  int nCost;                      /* Cost of running iterator */
  int bLookup;                    /* True if a lookup of a single entry. */

  /* Output values. Valid only after Fts3SegReaderStep() returns SQLITE_ROW. */
  char *zTerm;                    /* Pointer to term buffer */
  int nTerm;                      /* Size of zTerm in bytes */
  char *aDoclist;                 /* Pointer to doclist buffer */
  int nDoclist;                   /* Size of aDoclist[] in bytes */
};

/* fts3.c */
int sqlite3Fts3PutVarint(char *, sqlite3_int64);
int sqlite3Fts3GetVarint(const char *, sqlite_int64 *);
int sqlite3Fts3GetVarint32(const char *, int *);
int sqlite3Fts3VarintLen(sqlite3_uint64);
void sqlite3Fts3Dequote(char *);


int sqlite3Fts3ExprLoadDoclist(Fts3Cursor *, Fts3Expr *);
int sqlite3Fts3ExprLoadFtDoclist(Fts3Cursor *, Fts3Expr *, char **, int *);
int sqlite3Fts3ExprNearTrim(Fts3Expr *, Fts3Expr *, int);

/* fts3_tokenizer.c */
const char *sqlite3Fts3NextToken(const char *, int *);
int sqlite3Fts3InitHashTable(sqlite3 *, Fts3Hash *, const char *);

int sqlite3Fts3ExprInitTestInterface(sqlite3 *db);
int sqlite3Fts3InitTerm(sqlite3 *db);
#endif

/* fts3_aux.c */
int sqlite3Fts3InitAux(sqlite3 *db);

int sqlite3Fts3TermSegReaderCursor(
  Fts3Cursor *pCsr,               /* Virtual table cursor handle */
  const char *zTerm,              /* Term to query for */
  int nTerm,                      /* Size of zTerm in bytes */
  int isPrefix,                   /* True for a prefix search */
  Fts3MultiSegReader **ppSegcsr   /* OUT: Allocated seg-reader cursor */
);

int sqlite3Fts3EvalPhraseCache(Fts3Cursor *, Fts3Phrase *);
sqlite3_int64 sqlite3Fts3EvalDocid(Fts3Cursor *, Fts3Expr *);
int sqlite3Fts3EvalPhraseDoclist(Fts3Cursor*, Fts3Expr*, const char**,int*);
void sqlite3Fts3EvalPhraseCleanup(Fts3Phrase *);

int sqlite3Fts3EvalStart(Fts3Cursor *, Fts3Expr *, int);
int sqlite3Fts3EvalNext(Fts3Cursor *pCsr, Fts3Expr *pExpr);
int sqlite3Fts3MsrIncrStart(
    Fts3Table*, Fts3MultiSegReader*, int, const char*, int);
int sqlite3Fts3MsrIncrNext(
    Fts3Table *, Fts3MultiSegReader *, sqlite3_int64 *, char **, int *);
char *sqlite3Fts3EvalPhrasePoslist(
  Fts3Cursor *, Fts3Expr *, sqlite3_int64, int iCol); 
int sqlite3Fts3MsrOvfl(Fts3Cursor *, Fts3MultiSegReader *, int *);

int sqlite3Fts3DeferredTokenList(Fts3DeferredToken *, char **, int *);

#endif /* _FTSINT_H */

struct Fts3auxTable {
  sqlite3_vtab base;              /* Base class used by SQLite core */
  Fts3Table *pFts3Tab;
};

struct Fts3auxCursor {
  sqlite3_vtab_cursor base;       /* Base class used by SQLite core */
  Fts3MultiSegReader csr;        /* Must be right after "base" */
  Fts3SegFilter filter;
  char *zStop;
  int nStop;                      /* Byte-length of string zStop */
  int isEof;                      /* True if cursor is at EOF */
  sqlite3_int64 iRowid;           /* Current rowid */

  int iCol;                       /* Current value of 'col' column */

** Free a parsed fts3 query expression allocated by sqlite3Fts3ExprParse().
*/
void sqlite3Fts3ExprFree(Fts3Expr *p){
  if( p ){
    assert( p->eType==FTSQUERY_PHRASE || p->pPhrase==0 );
    sqlite3Fts3ExprFree(p->pLeft);
    sqlite3Fts3ExprFree(p->pRight);
    if( p->pPhrase ){
      sqlite3Fts3EvalPhraseCleanup(p->pPhrase);
      sqlite3_free(p->pPhrase->aDoclist);
    }
    sqlite3_free(p);
  }
}

/****************************************************************************
*****************************************************************************
** Everything after this point is just test code.

static int fts3SnippetFindPositions(Fts3Expr *pExpr, int iPhrase, void *ctx){
  SnippetIter *p = (SnippetIter *)ctx;
  SnippetPhrase *pPhrase = &p->aPhrase[iPhrase];
  char *pCsr;

  pPhrase->nToken = pExpr->pPhrase->nToken;

  pCsr = sqlite3Fts3EvalPhrasePoslist(p->pCsr, pExpr, p->pCsr->iPrevId,p->iCol);
  if( pCsr ){
    int iFirst = 0;
    pPhrase->pList = pCsr;
    fts3GetDeltaPosition(&pCsr, &iFirst);
    pPhrase->pHead = pCsr;
    pPhrase->pTail = pCsr;
    pPhrase->iHead = iFirst;

*/
static int fts3ExprGlobalHitsCb(
  Fts3Expr *pExpr,                /* Phrase expression node */
  int iPhrase,                    /* Phrase number (numbered from zero) */
  void *pCtx                      /* Pointer to MatchInfo structure */
){
  MatchInfo *p = (MatchInfo *)pCtx;





  u32 *aOut = &p->aMatchinfo[3*iPhrase*p->nCol];



  if( pExpr->bDeferred ){











    int iCol;                   /* Column index */
    for(iCol=0; iCol<p->nCol; iCol++){
      aOut[iCol*3 + 1] = (u32)p->nDoc;
      aOut[iCol*3 + 2] = (u32)p->nDoc;
    }


  }else{
    char *pIter;
    char *pEnd;
    int n;
    int rc = sqlite3Fts3EvalPhraseDoclist(
        p->pCursor, pExpr, (const char **)&pIter, &n
    );
    if( rc!=SQLITE_OK ) return rc;
    pEnd = &pIter[n];


    /* Fill in the global hit count matrix row for this phrase. */
    while( pIter<pEnd ){
      while( *pIter++ & 0x80 );      /* Skip past docid. */
      fts3LoadColumnlistCounts(&pIter, &aOut[1], 1);
    }
  }

  return SQLITE_OK;
}

/*
** fts3ExprIterate() callback used to collect the "local" part of the
** FTS3_MATCHINFO_HITS array. The local stats are those elements of the 
** array that are different for each row returned by the query.
*/
static int fts3ExprLocalHitsCb(
  Fts3Expr *pExpr,                /* Phrase expression node */
  int iPhrase,                    /* Phrase number */
  void *pCtx                      /* Pointer to MatchInfo structure */
){
  MatchInfo *p = (MatchInfo *)pCtx;
  int iStart = iPhrase * p->nCol * 3;
  int i;
  sqlite3_int64 iDocid = p->pCursor->iPrevId;

  for(i=0; i<p->nCol; i++){


    char *pCsr;
    pCsr = sqlite3Fts3EvalPhrasePoslist(p->pCursor, pExpr, iDocid, i);

    if( pCsr ){
      p->aMatchinfo[iStart+i*3] = fts3ColumnlistCount(&pCsr);
    }else{
      p->aMatchinfo[iStart+i*3] = 0;
    }
  }

  return SQLITE_OK;
}

static int fts3MatchinfoCheck(

** iterating through a multi-column position-list corresponding to the
** hits for a single phrase on a single row in order to calculate the
** values for a matchinfo() FTS3_MATCHINFO_LCS request.
*/
typedef struct LcsIterator LcsIterator;
struct LcsIterator {
  Fts3Expr *pExpr;                /* Pointer to phrase expression */

  int iPosOffset;                 /* Tokens count up to end of this phrase */
  char *pRead;                    /* Cursor used to iterate through aDoclist */
  int iPos;                       /* Current position */
};

/* 
** If LcsIterator.iCol is set to the following value, the iterator has
** finished iterating through all offsets for all columns.
*/

*/
static int fts3LcsIteratorAdvance(LcsIterator *pIter){
  char *pRead = pIter->pRead;
  sqlite3_int64 iRead;
  int rc = 0;

  pRead += sqlite3Fts3GetVarint(pRead, &iRead);
  if( iRead==0 || iRead==1 ){
    pRead = 0;
    rc = 1;
  }else{







    pIter->iPos += (int)(iRead-2);
  }

  pIter->pRead = pRead;
  return rc;
}
  

** undefined.
*/
static int fts3MatchinfoLcs(Fts3Cursor *pCsr, MatchInfo *pInfo){
  LcsIterator *aIter;
  int i;
  int iCol;
  int nToken = 0;
  sqlite3_int64 iDocid = pCsr->iPrevId;

  /* Allocate and populate the array of LcsIterator objects. The array
  ** contains one element for each matchable phrase in the query.
  **/
  aIter = sqlite3_malloc(sizeof(LcsIterator) * pCsr->nPhrase);
  if( !aIter ) return SQLITE_NOMEM;
  memset(aIter, 0, sizeof(LcsIterator) * pCsr->nPhrase);
  (void)fts3ExprIterate(pCsr->pExpr, fts3MatchinfoLcsCb, (void*)aIter);

  for(i=0; i<pInfo->nPhrase; i++){
    LcsIterator *pIter = &aIter[i];
    nToken -= pIter->pExpr->pPhrase->nToken;
    pIter->iPosOffset = nToken;







  }

  for(iCol=0; iCol<pInfo->nCol; iCol++){
    int nLcs = 0;                 /* LCS value for this column */
    int nLive = 0;                /* Number of iterators in aIter not at EOF */




    for(i=0; i<pInfo->nPhrase; i++){
      LcsIterator *pIt = &aIter[i];
      pIt->pRead = sqlite3Fts3EvalPhrasePoslist(pCsr, pIt->pExpr, iDocid, iCol);
      if( pIt->pRead ){
        pIt->iPos = pIt->iPosOffset;
        fts3LcsIteratorAdvance(&aIter[i]);
        nLive++;
      }
    }




    while( nLive>0 ){
      LcsIterator *pAdv = 0;      /* The iterator to advance by one position */
      int nThisLcs = 0;           /* LCS for the current iterator positions */

      for(i=0; i<pInfo->nPhrase; i++){
        LcsIterator *pIter = &aIter[i];
        if( pIter->pRead==0 ){
          /* This iterator is already at EOF for this column. */
          nThisLcs = 0;
        }else{
          if( pAdv==0 || pIter->iPos<pAdv->iPos ){
            pAdv = pIter;
          }
          if( nThisLcs==0 || pIter->iPos==pIter[-1].iPos ){

  TermOffsetCtx *p = (TermOffsetCtx *)ctx;
  int nTerm;                      /* Number of tokens in phrase */
  int iTerm;                      /* For looping through nTerm phrase terms */
  char *pList;                    /* Pointer to position list for phrase */
  int iPos = 0;                   /* First position in position-list */

  UNUSED_PARAMETER(iPhrase);
  pList = sqlite3Fts3EvalPhrasePoslist(p->pCsr, pExpr, p->iDocid, p->iCol);
  nTerm = pExpr->pPhrase->nToken;
  if( pList ){
    fts3GetDeltaPosition(&pList, &iPos);
    assert( iPos>=0 );
  }

  for(iTerm=0; iTerm<nTerm; iTerm++){

  sqlite3_vtab base;              /* Base class used by SQLite core */
  int iIndex;                     /* Index for Fts3Table.aIndex[] */
  Fts3Table *pFts3Tab;
};

struct Fts3termCursor {
  sqlite3_vtab_cursor base;       /* Base class used by SQLite core */
  Fts3MultiSegReader csr;        /* Must be right after "base" */
  Fts3SegFilter filter;

  int isEof;                      /* True if cursor is at EOF */
  char *pNext;

  sqlite3_int64 iRowid;           /* Current 'rowid' value */
  sqlite3_int64 iDocid;           /* Current 'docid' value */

  Fts3SegReader *pReader,         /* Segment-reader handle */
  int *pnCost                     /* IN/OUT: Number of bytes read */
){
  Fts3Table *p = (Fts3Table*)pCsr->base.pVtab;
  int rc = SQLITE_OK;             /* Return code */
  int nCost = 0;                  /* Cost in bytes to return */
  int pgsz = p->nPgsz;            /* Database page size */

  assert( pgsz>0 );

  /* If this seg-reader is reading the pending-terms table, or if all data
  ** for the segment is stored on the root page of the b-tree, then the cost
  ** is zero. In this case all required data is already in main memory.
  */
  if( p->bHasStat 
   && !fts3SegReaderIsPending(pReader) 

      }
    }
  }

  *pnCost += nCost;
  return rc;
}

int sqlite3Fts3MsrOvfl(
  Fts3Cursor *pCsr, 
  Fts3MultiSegReader *pMsr,
  int *pnOvfl
){
  Fts3Table *p = (Fts3Table*)pCsr->base.pVtab;
  int nOvfl = 0;
  int ii;
  int rc = SQLITE_OK;
  int pgsz = p->nPgsz;

  assert( p->bHasStat );
  assert( pgsz>0 );

  for(ii=0; rc==SQLITE_OK && ii<pMsr->nSegment; ii++){
    Fts3SegReader *pReader = pMsr->apSegment[ii];
    if( !fts3SegReaderIsPending(pReader) 
     && !fts3SegReaderIsRootOnly(pReader) 
    ){
      int jj;
      for(jj=pReader->iStartBlock; jj<=pReader->iLeafEndBlock; jj++){
        int nBlob;
        rc = sqlite3Fts3ReadBlock(p, jj, 0, &nBlob);
        if( rc!=SQLITE_OK ) break;
        if( (nBlob+35)>pgsz ){
          nOvfl += (nBlob + 34)/pgsz;
        }
      }
    }
  }
  *pnOvfl = nOvfl;
  return rc;
}

/*
** Free all allocations associated with the iterator passed as the 
** second argument.
*/
void sqlite3Fts3SegReaderFree(Fts3SegReader *pReader){
  if( pReader && !fts3SegReaderIsPending(pReader) ){

    p = &pList[1];
    p += sqlite3Fts3GetVarint32(p, &iCurrent);
  }

  *ppList = pList;
  *pnList = nList;
}

int sqlite3Fts3MsrIncrStart(
  Fts3Table *p,                   /* Virtual table handle */
  Fts3MultiSegReader *pCsr,       /* Cursor object */
  int iCol,                       /* Column to match on. */
  const char *zTerm,              /* Term to iterate through a doclist for */
  int nTerm                       /* Number of bytes in zTerm */
){
  int i;
  int nSegment = pCsr->nSegment;

  assert( pCsr->pFilter==0 );
  assert( zTerm && nTerm>0 );

  /* Advance each segment iterator until it points to the term zTerm/nTerm. */
  for(i=0; i<nSegment; i++){
    Fts3SegReader *pSeg = pCsr->apSegment[i];
    do {
      int rc = fts3SegReaderNext(p, pSeg);
      if( rc!=SQLITE_OK ) return rc;
    }while( fts3SegReaderTermCmp(pSeg, zTerm, nTerm)<0 );
  }
  fts3SegReaderSort(pCsr->apSegment, nSegment, nSegment, fts3SegReaderCmp);

  /* Determine how many of the segments actually point to zTerm/nTerm. */
  for(i=0; i<nSegment; i++){
    Fts3SegReader *pSeg = pCsr->apSegment[i];
    if( !pSeg->aNode || fts3SegReaderTermCmp(pSeg, zTerm, nTerm) ){
      break;
    }
  }
  pCsr->nAdvance = i;

  /* Advance each of the segments to point to the first docid. */
  for(i=0; i<pCsr->nAdvance; i++){
    fts3SegReaderFirstDocid(pCsr->apSegment[i]);
  }

  assert( iCol<0 || iCol<p->nColumn );
  pCsr->iColFilter = iCol;

  return SQLITE_OK;
}

int sqlite3Fts3MsrIncrNext(
  Fts3Table *p,                   /* Virtual table handle */
  Fts3MultiSegReader *pMsr,       /* Multi-segment-reader handle */
  sqlite3_int64 *piDocid,         /* OUT: Docid value */
  char **paPoslist,               /* OUT: Pointer to position list */
  int *pnPoslist                  /* OUT: Size of position list in bytes */
){
  int rc = SQLITE_OK;
  int nMerge = pMsr->nAdvance;
  Fts3SegReader **apSegment = pMsr->apSegment;

  if( nMerge==0 ){
    *paPoslist = 0;
    return SQLITE_OK;
  }

  while( 1 ){
    Fts3SegReader *pSeg;
    fts3SegReaderSort(pMsr->apSegment, nMerge, nMerge, fts3SegReaderDoclistCmp);
    pSeg = pMsr->apSegment[0];

    if( pSeg->pOffsetList==0 ){
      *paPoslist = 0;
      break;
    }else{
      char *pList;
      int nList;
      int j;
      sqlite3_int64 iDocid = apSegment[0]->iDocid;

      fts3SegReaderNextDocid(apSegment[0], &pList, &nList);
      j = 1;
      while( j<nMerge
        && apSegment[j]->pOffsetList
        && apSegment[j]->iDocid==iDocid
      ){
        fts3SegReaderNextDocid(apSegment[j], 0, 0);
      }

      if( pMsr->iColFilter>=0 ){
        fts3ColumnFilter(pMsr->iColFilter, &pList, &nList);
      }

      if( nList>0 ){
        *piDocid = iDocid;
        *paPoslist = pList;
        *pnPoslist = nList;
        break;
      }
    }
  }

  return rc;
}

int sqlite3Fts3SegReaderStart(
  Fts3Table *p,                   /* Virtual table handle */
  Fts3MultiSegReader *pCsr,       /* Cursor object */
  Fts3SegFilter *pFilter          /* Restrictions on range of iteration */
){
  int i;

  /* Initialize the cursor object */
  pCsr->pFilter = pFilter;

      pCsr->apSegment, pCsr->nSegment, pCsr->nSegment, fts3SegReaderCmp);

  return SQLITE_OK;
}

int sqlite3Fts3SegReaderStep(
  Fts3Table *p,                   /* Virtual table handle */
  Fts3MultiSegReader *pCsr        /* Cursor object */
){
  int rc = SQLITE_OK;

  int isIgnoreEmpty =  (pCsr->pFilter->flags & FTS3_SEGMENT_IGNORE_EMPTY);
  int isRequirePos =   (pCsr->pFilter->flags & FTS3_SEGMENT_REQUIRE_POS);
  int isColFilter =    (pCsr->pFilter->flags & FTS3_SEGMENT_COLUMN_FILTER);
  int isPrefix =       (pCsr->pFilter->flags & FTS3_SEGMENT_PREFIX);

      }
    }
    pCsr->nAdvance = nMerge;
  }while( rc==SQLITE_OK );

  return rc;
}


void sqlite3Fts3SegReaderFinish(
  Fts3MultiSegReader *pCsr       /* Cursor object */
){
  if( pCsr ){
    int i;
    for(i=0; i<pCsr->nSegment; i++){
      sqlite3Fts3SegReaderFree(pCsr->apSegment[i]);
    }
    sqlite3_free(pCsr->apSegment);

*/
static int fts3SegmentMerge(Fts3Table *p, int iIndex, int iLevel){
  int rc;                         /* Return code */
  int iIdx = 0;                   /* Index of new segment */
  int iNewLevel = 0;              /* Level/index to create new segment at */
  SegmentWriter *pWriter = 0;     /* Used to write the new, merged, segment */
  Fts3SegFilter filter;           /* Segment term filter condition */
  Fts3MultiSegReader csr;        /* Cursor to iterate through level(s) */
  int bIgnoreEmpty = 0;           /* True to ignore empty segments */

  assert( iLevel==FTS3_SEGCURSOR_ALL
       || iLevel==FTS3_SEGCURSOR_PENDING
       || iLevel>=0
  );
  assert( iLevel<FTS3_SEGDIR_MAXLEVEL );

        rc = fts3PendingListAppendVarint(&pDef->pList, 0);
      }
    }
  }

  return rc;
}

int sqlite3Fts3DeferredTokenList(
  Fts3DeferredToken *p, 
  char **ppData, 
  int *pnData
){
  char *pRet;
  int nSkip;
  sqlite3_int64 dummy;

  *ppData = 0;
  *pnData = 0;

  if( p->pList==0 ){
    return SQLITE_OK;
  }

  pRet = (char *)sqlite3_malloc(p->pList->nData);
  if( !pRet ) return SQLITE_NOMEM;

  nSkip = sqlite3Fts3GetVarint(p->pList->aData, &dummy);
  *pnData = p->pList->nData - nSkip;
  *ppData = pRet;
  
  memcpy(pRet, &p->pList->aData[nSkip], *pnData);
  return SQLITE_OK;
}

/*
** Add an entry for token pToken to the pCsr->pDeferred list.
*/
int sqlite3Fts3DeferToken(
  Fts3Cursor *pCsr,               /* Fts3 table cursor */
  Fts3PhraseToken *pToken,        /* Token to defer */

ifcapable !fts3 {
  finish_test
  return
}

set sqlite_fts3_enable_parentheses 1

set fts3_simple_deferred_tokens_only 1

set ::testprefix fts3defer

#--------------------------------------------------------------------------
# Test cases fts3defer-1.* are the "warm body" cases. The database contains
# one row with 15000 instances of the token "a". This makes the doclist for
# "a" so large that FTS3 will avoid loading it in most cases.
#

  do_select_test 1.1 {
    SELECT rowid FROM t1 WHERE t1 MATCH 'jk xnxhf'
  } {13 29 40 47 48 52 63 92}
  do_select_test 1.2 {
    SELECT rowid FROM t1 WHERE t1 MATCH 'jk eh'
  } {100}

  do_select_test 1.3 {
    SELECT rowid FROM t1 WHERE t1 MATCH 'jk ubwrfqnbjf'
  } {7 70 98}
  do_select_test 1.4 {
    SELECT rowid FROM t1 WHERE t1 MATCH 'duszemmzl jk'
  } {3 5 8 10 13 18 20 23 32 37 41 43 55 60 65 67 72 74 76 81 94 96 97}
  do_select_test 1.5 {

  } {68 100}
  do_select_test 1.9 {
    SELECT rowid FROM t1 WHERE t1 MATCH 'zm ubwrfqnbjf'
  } {7 70 98}
  do_select_test 1.10 {
    SELECT rowid FROM t1 WHERE t1 MATCH 'z* vgsld'
  } {10 13 17 31 35 51 58 88 89 90 93 100}

  if { $fts3_simple_deferred_tokens_only==0 } {
    do_select_test 1.11 {
      SELECT rowid FROM t1 
      WHERE t1 MATCH '(
        zdu OR zexh OR zf OR zhbrzadb OR zidhxhbtv OR 
        zk OR zkhdvkw OR zm OR zsmhnf
      ) vgsld'
    } {10 13 17 31 35 51 58 88 89 90 93 100}
  }

  do_select_test 2.1 {
    SELECT rowid FROM t1 WHERE t1 MATCH '"zm agmckuiu"'
  } {3 24 52 53}
  do_select_test 2.2 {
    SELECT rowid FROM t1 WHERE t1 MATCH '"zm zf"'
  } {33 53 75 88 101}

  # The following block of tests runs normally with FTS3 or FTS4 without the
  # long doclists zeroed. And with OOM-injection for FTS4 with long doclists
  # zeroed. Change this by messing with the [set dmt_modes] commands above.
  #
  foreach DO_MALLOC_TEST $dmt_modes {
    
    # Phrase search.
    #
    do_select_test 5.$DO_MALLOC_TEST.1 {
      SELECT rowid FROM t1 WHERE t1 MATCH '"jk mjpavjuhw"'
    } {8 15 36 64 67 72}

    # Multiple tokens search.
    do_select_test 5.$DO_MALLOC_TEST.2 {
      SELECT rowid FROM t1 WHERE t1 MATCH 'duszemmzl zm'

  } {10}
  do_select_test 6.2.1 {
    SELECT rowid FROM t1 WHERE t1 MATCH '"jk xduvfhk"'
  } {8}
  do_select_test 6.2.2 {
    SELECT rowid FROM t1 WHERE t1 MATCH '"zm azavwm"'
  } {15 26 92 96}
  if {$fts3_simple_deferred_tokens_only==0} {
    do_select_test 6.2.3 {
      SELECT rowid FROM t1 WHERE t1 MATCH '"jk xduvfhk" OR "zm azavwm"'
    } {8 15 26 92 96}
  }
}

set testprefix fts3defer

do_execsql_test 3.1 {
  CREATE VIRTUAL TABLE x1 USING fts4(a, b);
  INSERT INTO x1 VALUES('a b c', 'd e f');

} -files {
  fts3aa.test fts3ab.test fts3ac.test fts3ad.test fts3ae.test
  fts3af.test fts3ag.test fts3ah.test fts3ai.test fts3aj.test
  fts3ak.test fts3al.test fts3am.test fts3an.test fts3ao.test
  fts3atoken.test fts3b.test fts3c.test fts3cov.test fts3d.test
  fts3defer.test fts3defer2.test fts3e.test fts3expr.test fts3expr2.test 
  fts3near.test fts3query.test fts3shared.test fts3snippet.test 
  fts3sort.test

  fts3fault.test fts3malloc.test fts3matchinfo.test

  fts3aux1.test fts3comp1.test
}