SQLite

      sqlite3_free(aPoslist);
    }
  }

  return SQLITE_OK;
}

/*
** Maximum number of tokens a phrase may have to be considered for the
** incremental doclists strategy.
*/
#define MAX_INCR_PHRASE_TOKENS 4

/*
** This function is called for each Fts3Phrase in a full-text query 
** expression to initialize the mechanism for returning rows. Once this
** function has been called successfully on an Fts3Phrase, it may be
** used with fts3EvalPhraseNext() to iterate through the matching docids.
**
** If parameter bOptOk is true, then the phrase may (or may not) use the
** incremental loading strategy. Otherwise, the entire doclist is loaded into
** memory within this call.
**
** SQLITE_OK is returned if no error occurs, otherwise an SQLite error code.
*/
static int fts3EvalPhraseStart(Fts3Cursor *pCsr, int bOptOk, Fts3Phrase *p){


  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
  int rc = SQLITE_OK;             /* Error code */
  int i;

  /* Determine if doclists may be loaded from disk incrementally. This is
  ** possible if the bOptOk argument is true, the FTS doclists will be
  ** scanned in forward order, and the phrase consists of 
  ** MAX_INCR_PHRASE_TOKENS or fewer tokens, none of which are are "^first"
  ** tokens or prefix tokens that cannot use a prefix-index.  */
  int bIncrOk = (bOptOk 
   && pCsr->bDesc==pTab->bDescIdx 

   && p->nToken<=MAX_INCR_PHRASE_TOKENS && p->nToken>0
  );
  for(i=0; bIncrOk==1 && i<p->nToken; i++){
    Fts3PhraseToken *pToken = &p->aToken[i];
    if( pToken->bFirst || !pToken->pSegcsr || !pToken->pSegcsr->bLookup ){
      bIncrOk = 0;
    }
  }

  if( bIncrOk ){
    /* Use the incremental approach. */
    int iCol = (p->iColumn >= pTab->nColumn ? -1 : p->iColumn);
    for(i=0; rc==SQLITE_OK && i<p->nToken; i++){
      Fts3PhraseToken *pTok = &p->aToken[i];
      rc = sqlite3Fts3MsrIncrStart(pTab, pTok->pSegcsr, iCol, pTok->z, pTok->n);


    }
  }else{
    /* Load the full doclist for the phrase into memory. */
    rc = fts3EvalPhraseLoad(pCsr, p);

  }
  p->bIncr = bIncrOk;

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

/*
** This function is used to iterate backwards (from the end to start) 

      p += sqlite3Fts3GetVarint(p, &iVar);
      *piDocid += ((bDescIdx ? -1 : 1) * iVar);
    }
  }

  *ppIter = p;
}

/*
** Helper type used by fts3EvalIncrPhraseNext() and incrPhraseTokenNext().
*/
typedef struct TokenDoclist TokenDoclist;
struct TokenDoclist {
  sqlite3_int64 iDocid;
  char *pList;
  int nList;
};

/*
** Token pToken is an incrementally loaded token that is part of a 
** multi-token phrase. Advance it to the next matching document in the
** database and populate output variable *p with the details of the new
** entry. Or, if the iterator has reached EOF, set *pbEof to true.
**
** If an error occurs, return an SQLite error code. Otherwise, return 
** SQLITE_OK.
*/
static int incrPhraseTokenNext(
  Fts3Table *pTab,                /* Virtual table handle */
  Fts3PhraseToken *pToken,        /* Advance the iterator for this token */
  TokenDoclist *p,                /* OUT: Docid and doclist for new entry */
  int *pbEof                      /* OUT: True if iterator is at EOF */
){
  int rc;
  assert( pToken->pDeferred==0 );
  rc = sqlite3Fts3MsrIncrNext(
      pTab, pToken->pSegcsr, &p->iDocid, &p->pList, &p->nList
  );
  if( p->pList==0 ) *pbEof = 1;
  return rc;
}


/*
** The phrase iterator passed as the second argument uses the incremental
** doclist strategy. Advance it to the next matching documnent in the
** database. 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 fts3EvalIncrPhraseNext(
  Fts3Cursor *pCsr,               /* FTS Cursor handle */
  Fts3Phrase *p,                  /* Phrase object to advance to next docid */
  u8 *pbEof                       /* OUT: Set to 1 if EOF */
){
  int rc = SQLITE_OK;
  Fts3Doclist *pDL = &p->doclist;
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
  int bEof = 0;

  assert( p->bIncr==1 );
  assert( pDL->pNextDocid==0 );

  if( p->nToken==1 ){
    rc = sqlite3Fts3MsrIncrNext(pTab, p->aToken[0].pSegcsr, 
        &pDL->iDocid, &pDL->pList, &pDL->nList
    );
    if( pDL->pList==0 ) bEof = 1;
  }else{
    int bDescDoclist = pCsr->bDesc;
    struct TokenDoclist a[MAX_INCR_PHRASE_TOKENS];

    assert( p->nToken<=MAX_INCR_PHRASE_TOKENS );

    while( bEof==0 ){
      sqlite3_int64 iMax;         /* Largest docid for all iterators */
      int i;                      /* Used to iterate through tokens */

      /* Advance the iterator for each token in the phrase once. */
      for(i=0; rc==SQLITE_OK && i<p->nToken; i++){
        rc = incrPhraseTokenNext(pTab, &p->aToken[i], &a[i], &bEof);
        if( i==0 || DOCID_CMP(iMax, a[i].iDocid)<0 ){
          iMax = a[i].iDocid;
        }
      }

      /* Keep advancing iterators until they all point to the same document */
      if( bEof==0 && rc==SQLITE_OK ){
        for(i=0; i<p->nToken; i++){
          while( DOCID_CMP(a[i].iDocid, iMax)<0 && rc==SQLITE_OK && bEof==0 ){
            rc = incrPhraseTokenNext(pTab, &p->aToken[i], &a[i], &bEof);
            if( DOCID_CMP(a[i].iDocid, iMax)>0 ){
              iMax = a[i].iDocid;
              i = 0;
            }
          }
        }
      }

      /* Check if the current entries really are a phrase match */
      if( bEof==0 ){
        int nByte = a[p->nToken-1].nList;
        char *aDoclist = sqlite3_malloc(nByte+1);
        if( !aDoclist ) return SQLITE_NOMEM;
        memcpy(aDoclist, a[p->nToken-1].pList, nByte+1);

        int nList;
        for(i=0; i<(p->nToken-1); i++){
          char *pLeft = a[i].pList;
          char *pRight = aDoclist;
          char *pOut = aDoclist;
          int nDist = p->nToken-1-i;
          int res = fts3PoslistPhraseMerge(&pOut, nDist, 0, 1, &pLeft, &pRight);
          if( res==0 ) break;
          nList = (pOut - aDoclist);
        }
        if( i==(p->nToken-1) ){
          pDL->iDocid = a[0].iDocid;
          pDL->pList = aDoclist;
          pDL->nList = nList;
          pDL->bFreeList = 1;
          break;
        }
        sqlite3_free(aDoclist);
      }
    }
  }

  *pbEof = bEof;
  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,               /* FTS Cursor handle */
  Fts3Phrase *p,                  /* Phrase object to advance to next docid */
  u8 *pbEof                       /* OUT: Set to 1 if EOF */
){
  int rc = SQLITE_OK;
  Fts3Doclist *pDL = &p->doclist;
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;

  if( p->bIncr ){






    rc = fts3EvalIncrPhraseNext(pCsr, p, pbEof);

  }else if( pCsr->bDesc!=pTab->bDescIdx && pDL->nAll ){
    sqlite3Fts3DoclistPrev(pTab->bDescIdx, pDL->aAll, pDL->nAll, 
        &pDL->pNextDocid, &pDL->iDocid, &pDL->nList, pbEof
    );
    pDL->pList = pDL->pNextDocid;
  }else{
    char *pIter;                            /* Used to iterate through aAll */

**
** If an error occurs within this function, *pRc is set to an SQLite error
** code before returning.
*/
static void fts3EvalStartReaders(
  Fts3Cursor *pCsr,               /* FTS Cursor handle */
  Fts3Expr *pExpr,                /* Expression to initialize phrases in */

  int *pRc                        /* IN/OUT: Error code */
){
  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, 1, pExpr->pPhrase);
    }else{
      fts3EvalStartReaders(pCsr, pExpr->pLeft, pRc);
      fts3EvalStartReaders(pCsr, pExpr->pRight, pRc);
      pExpr->bDeferred = (pExpr->pLeft->bDeferred && pExpr->pRight->bDeferred);
    }
  }
}

/*
** An array of the following structures is assembled as part of the process

      }

      sqlite3_free(aTC);
    }
  }
#endif

  fts3EvalStartReaders(pCsr, pCsr->pExpr, &rc);
  return rc;
}

/*
** Invalidate the current position list for phrase pPhrase.
*/
static void fts3EvalInvalidatePoslist(Fts3Phrase *pPhrase){

){
  if( pExpr && *pRc==SQLITE_OK ){
    Fts3Phrase *pPhrase = pExpr->pPhrase;

    if( pPhrase ){
      fts3EvalInvalidatePoslist(pPhrase);
      if( pPhrase->bIncr ){
        int i;
        for(i=0; i<pPhrase->nToken; i++){
          assert( pPhrase->aToken[i].pSegcsr );
          sqlite3Fts3MsrIncrRestart(pPhrase->aToken[i].pSegcsr);
        }
        *pRc = fts3EvalPhraseStart(pCsr, 0, pPhrase);
      }

      pPhrase->doclist.pNextDocid = 0;
      pPhrase->doclist.iDocid = 0;
    }

    pExpr->iDocid = 0;
    pExpr->bEof = 0;
    pExpr->bStart = 0;