** database. TODO: For xConnect(), it could verify that said tables exist.
  */
  if( isCreate ){
    rc = fts3CreateTables(p);
  }

  /* Figure out the page-size for the database. This is required in order to
  ** estimate the cost of loading large doclists from the database (see 
  ** function sqlite3Fts3SegReaderCost() for details).
  */
  fts3DatabasePageSize(&rc, p);
  p->nNodeSize = p->nPgsz-35;

  /* Declare the table schema to SQLite. */
  fts3DeclareVtab(&rc, p);

fts3_init_out:
................................................................................
  *pbFirst = 1;
}

#define COMPARE_DOCID(i1, i2) ((bDescIdx?-1:1) * (i1-i2))

static int fts3DoclistOrMerge(
  int bDescIdx,                   /* True if arguments are desc */
  u8 *a1, int n1,                 /* First doclist */
  u8 *a2, int n2,                 /* Second doclist */
  u8 **paOut, int *pnOut          /* OUT: Malloc'd doclist */
){
  sqlite3_int64 i1 = 0;
  sqlite3_int64 i2 = 0;
  sqlite3_int64 iPrev = 0;
  char *pEnd1 = &a1[n1];
  char *pEnd2 = &a2[n2];
  char *p1 = a1;
  char *p2 = a2;
  char *p;
  int nOut;
  char *aOut;
  int bFirstOut = 0;

  *paOut = 0;
  *pnOut = 0;
  aOut = sqlite3_malloc(n1+n2);
  if( !aOut ) return SQLITE_NOMEM;
................................................................................
  *pnOut = (p-aOut);
  return SQLITE_OK;
}

static void fts3DoclistPhraseMerge(
  int bDescIdx,                   /* True if arguments are desc */
  int nDist,                      /* Distance from left to right (1=adjacent) */
  u8 *aLeft, int nLeft,           /* Left doclist */
  u8 *aRight, int *pnRight        /* IN/OUT: Right/output doclist */
){
  sqlite3_int64 i1 = 0;
  sqlite3_int64 i2 = 0;
  sqlite3_int64 iPrev = 0;
  char *pEnd1 = &aLeft[nLeft];
  char *pEnd2 = &aRight[*pnRight];
  char *p1 = aLeft;
................................................................................
      fts3PoslistCopy(0, &p2);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescIdx, &i2);
    }
  }

  *pnRight = p - aOut;
}

/*
** This function merges two doclists according to the requirements of a
** NEAR operator.
*/
static int fts3DoclistNearMerge(
  int bDescIdx,
  int nNear,                      /* Parameter to NEAR operator */
  int nTokenLeft,                 /* Number of tokens in LHS phrase arg */
  char *aLeft,                    /* Doclist for LHS (incl. positions) */
  int nLeft,                      /* Size of LHS doclist in bytes */
  int nTokenRight,                /* As nTokenLeft */
  char *aRight,                   /* As aLeft */
  int nRight,                     /* As nRight */
  char **paOut,                   /* OUT: Results of merge (malloced) */
  int *pnOut                      /* OUT: Sized of output buffer */
){
  char *aOut;                     /* Buffer to write output doclist to */
  char *aTmp;                     /* Temp buffer used by PoslistNearMerge() */

  sqlite3_int64 i1 = 0;
  sqlite3_int64 i2 = 0;
  sqlite3_int64 iPrev = 0;
  int bFirstOut = 0;

  char *pEnd1 = &aLeft[nLeft];
  char *pEnd2 = &aRight[nRight];
  char *p1 = aLeft;
  char *p2 = aRight;
  char *p;

  int nParam1 = nNear+nTokenRight;
  int nParam2 = nNear+nTokenLeft;

  p = aOut = sqlite3_malloc(nLeft+nRight+1);
  aTmp = sqlite3_malloc(2*(nLeft+nRight+1));
  if( !aOut || !aTmp ){
    sqlite3_free(aOut);
    sqlite3_free(aTmp);
    *paOut = 0;
    *pnOut = 0;
    return SQLITE_NOMEM;
  }

  fts3GetDeltaVarint3(&p1, pEnd1, 0, &i1);
  fts3GetDeltaVarint3(&p2, pEnd2, 0, &i2);

  while( p1 && p2 ){
    sqlite3_int64 iDiff = COMPARE_DOCID(i1, i2);
    if( iDiff==0 ){
      char *pSave = p;
      sqlite3_int64 iPrevSave = iPrev;
      int bFirstOutSave = bFirstOut;
      fts3PutDeltaVarint3(&p, bDescIdx, &iPrev, &bFirstOut, i1);
      if( !fts3PoslistNearMerge(&p, aTmp, nParam1, nParam2, &p1, &p2) ){
        p = pSave;
        iPrev = iPrevSave;
        bFirstOut = bFirstOutSave;
      }

      fts3GetDeltaVarint3(&p1, pEnd1, bDescIdx, &i1);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescIdx, &i2);
    }else if( iDiff<0 ){
      fts3PoslistCopy(0, &p1);
      fts3GetDeltaVarint3(&p1, pEnd1, bDescIdx, &i1);
    }else{
      fts3PoslistCopy(0, &p2);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescIdx, &i2);
    }
  }

  sqlite3_free(aTmp);
  *paOut = aOut;
  *pnOut = p - aOut;
  return SQLITE_OK;
}



/*
** Merge all doclists in the TermSelect.aaOutput[] array into a single
** doclist stored in TermSelect.aaOutput[0]. If successful, delete all
** other doclists (except the aaOutput[0] one) and return SQLITE_OK.
**
................................................................................
    if( pTS->aaOutput[i] ){
      if( !aOut ){
        aOut = pTS->aaOutput[i];
        nOut = pTS->anOutput[i];
        pTS->aaOutput[i] = 0;
      }else{
        int nNew;
        u8 *aNew;

        int rc = fts3DoclistOrMerge(p->bDescIdx, 
            pTS->aaOutput[i], pTS->anOutput[i], aOut, nOut, &aNew, &nNew
        );
        if( rc!=SQLITE_OK ){
          sqlite3_free(aOut);
          return rc;
................................................................................
    for(iOut=0; iOut<SizeofArray(pTS->aaOutput); iOut++){
      if( pTS->aaOutput[iOut]==0 ){
        assert( iOut>0 );
        pTS->aaOutput[iOut] = aMerge;
        pTS->anOutput[iOut] = nMerge;
        break;
      }else{
        u8 *aNew;
        int nNew;

        int rc = fts3DoclistOrMerge(p->bDescIdx, aMerge, nMerge, 
            pTS->aaOutput[iOut], pTS->anOutput[iOut], &aNew, &nNew
        );
        if( rc!=SQLITE_OK ){
          if( aMerge!=aDoclist ) sqlite3_free(aMerge);
................................................................................
){
  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;
................................................................................

    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){
................................................................................
    "ALTER TABLE %Q.'%q_segdir'   RENAME TO '%q_segdir';",
    p->zDb, p->zName, zName
  );
  return rc;
}

static int fts3SavepointMethod(sqlite3_vtab *pVtab, int iSavepoint){
  Fts3Table *p = (Fts3Table*)pVtab;
  UNUSED_PARAMETER(iSavepoint);
  assert( p->inTransaction );
  assert( p->mxSavepoint < iSavepoint );
  TESTONLY( p->mxSavepoint = iSavepoint );
  return fts3SyncMethod(pVtab);
}
static int fts3ReleaseMethod(sqlite3_vtab *pVtab, int iSavepoint){
  TESTONLY( Fts3Table *p = (Fts3Table*)pVtab );
  UNUSED_PARAMETER(iSavepoint);
  UNUSED_PARAMETER(pVtab);
  assert( p->inTransaction );
................................................................................
  }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;
................................................................................
** 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.
*/
static int fts3EvalPhraseStart(Fts3Cursor *pCsr, int bOptOk, Fts3Phrase *p){
  int rc;
  Fts3Doclist *pList = &p->doclist;
  Fts3PhraseToken *pFirst = &p->aToken[0];
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;

  assert( pList->aAll==0 );

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

    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{
      sqlite3_int64 iDelta;
      pIter += sqlite3Fts3GetVarint(pIter, &iDelta);
      if( pTab->bDescIdx==0 || pDL->pNextDocid==0 ){
        pDL->iDocid += iDelta;
      }else{
        pDL->iDocid -= iDelta;
      }
      pDL->pList = pIter;
      fts3PoslistCopy(0, &pIter);
      pDL->nList = (pIter - pDL->pList);









      pDL->pNextDocid = pIter;

      *pbEof = 0;
    }
  }

  return rc;
}

................................................................................
      fts3EvalStartReaders(pCsr, pExpr->pLeft, bOptOk, pRc);
      fts3EvalStartReaders(pCsr, pExpr->pRight, bOptOk, pRc);
      pExpr->bDeferred = (pExpr->pLeft->bDeferred && pExpr->pRight->bDeferred);
    }
  }
}

static void fts3EvalNearMerge(
  int bDescIdx,
  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 = fts3DoclistNearMerge(bDescIdx, 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{
        Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;
        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(p->bDescIdx, aPhrase[i], aPhrase[i+1], nNear, pRc);
        }
        for(i=nPhrase-2; i>=0; i--){
          int nNear = aPhrase[i+1]->pParent->nNear;
          fts3EvalNearMerge(p->bDescIdx, 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;
  Fts3Expr *pRoot;
  int nOvfl;
  int iCol;
................................................................................
      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;
................................................................................
    );
    apOr = (Fts3Expr **)&aTC[nToken];

    if( !aTC ){
      rc = SQLITE_NOMEM;
    }else{
      int ii;
      int nDocSize;
      Fts3TokenAndCost *pTC = aTC;
      Fts3Expr **ppOr = apOr;

      fts3EvalTokenCosts(pCsr, 0, pExpr, &pTC, &ppOr, &rc);
      nToken = pTC-aTC;
      nOr = ppOr-apOr;


      rc = fts3EvalSelectDeferred(pCsr, 0, aTC, nToken);
      for(ii=0; rc==SQLITE_OK && ii<nOr; ii++){
        rc = fts3EvalSelectDeferred(pCsr, apOr[ii], aTC, nToken);
      }

#if 0
      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;
      }
#endif

      sqlite3_free(aTC);
    }
  }

  fts3EvalStartReaders(pCsr, pExpr, bOptOk, &rc);
  return rc;
................................................................................
  char *aTmp,                     /* Temporary space to use */
  char **paPoslist,               /* IN/OUT: Position list */
  int *pnToken,                   /* IN/OUT: Tokens in phrase of *paPoslist */
  Fts3Phrase *pPhrase             /* The phrase object to trim the doclist of */
){
  int nParam1 = nNear + pPhrase->nToken;
  int nParam2 = nNear + *pnToken;

  char *p2; 
  char *pOut; 
  int res;

  p2 = pOut = pPhrase->doclist.pList;
  res = fts3PoslistNearMerge(
    &pOut, aTmp, nParam1, nParam2, paPoslist, &p2
  );

  pPhrase->doclist.nList = pOut - pPhrase->doclist.pList;




  *paPoslist = pPhrase->doclist.pList;
  *pnToken = pPhrase->nToken;


  return res;
}

static int fts3EvalNearTest(Fts3Expr *pExpr, int *pRc){
  int res = 1;

................................................................................
      pCsr->isMatchinfoNeeded = 1;
      pCsr->iPrevId = pExpr->iDocid;
    }while( pCsr->isEof==0 && fts3EvalLoadDeferred(pCsr, &rc) );
  }
  return rc;
}













































































































































/*
** Return a pointer to the entire doclist, including positions, associated 
** with the phrase passed as the second argument. It is illegal to call
** this function if the phrase consists entirely of deferred tokens.


**
** TODO: This function is only used by the code for the matchinfo('x')
** auxiliary function - to obtain the following two values:


**
**   1. The total number of times the phrase appears in each column in all 
**      rows in the FTS table.


**
**   2. For each column, the total number of rows in the FTS table for which
**      the phrase appears at least once in the column.


**
** It would be better if there was an sqlite3Fts3EvalXXX() function 
** specifically to retrieve these values. If that were done, the concept
** of which tokens are deferred or incremental would be entirely encapsulated
** within the sqlite3Fts3EvalXXX()/fts3EvalXXX() functions in this file.
















*/
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;


  /* It is illegal to call this function if the phrase is entirely deferred
  ** (it may contain some deferred tokens, but must also contain at least
  ** one token for which the doclist may be read from the full-text index). 
  */
  assert( !pExpr->bDeferred );





  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->bStart==0 || pExpr->iDocid!=iDocid) ){

        fts3EvalNext(pCsr, pExpr, &rc);

        assert( !pExpr->bEof );



      }
    }
  }

  if( rc==SQLITE_OK 
   && pExpr->pParent 
   && pExpr->pParent->eType==FTSQUERY_NEAR 
  ){

  }

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

/*
** The expression pExpr passed as the second argument to this function
** must be of type FTSQUERY_PHRASE. 
**

  ** database. TODO: For xConnect(), it could verify that said tables exist.
  */
  if( isCreate ){
    rc = fts3CreateTables(p);
  }

  /* Figure out the page-size for the database. This is required in order to
  ** estimate the cost of loading large doclists from the database.  */


  fts3DatabasePageSize(&rc, p);
  p->nNodeSize = p->nPgsz-35;

  /* Declare the table schema to SQLite. */
  fts3DeclareVtab(&rc, p);

fts3_init_out:
................................................................................
  *pbFirst = 1;
}

#define COMPARE_DOCID(i1, i2) ((bDescIdx?-1:1) * (i1-i2))

static int fts3DoclistOrMerge(
  int bDescIdx,                   /* True if arguments are desc */
  char *a1, int n1,               /* First doclist */
  char *a2, int n2,               /* Second doclist */
  char **paOut, int *pnOut        /* OUT: Malloc'd doclist */
){
  sqlite3_int64 i1 = 0;
  sqlite3_int64 i2 = 0;
  sqlite3_int64 iPrev = 0;
  char *pEnd1 = &a1[n1];
  char *pEnd2 = &a2[n2];
  char *p1 = a1;
  char *p2 = a2;
  char *p;

  char *aOut;
  int bFirstOut = 0;

  *paOut = 0;
  *pnOut = 0;
  aOut = sqlite3_malloc(n1+n2);
  if( !aOut ) return SQLITE_NOMEM;
................................................................................
  *pnOut = (p-aOut);
  return SQLITE_OK;
}

static void fts3DoclistPhraseMerge(
  int bDescIdx,                   /* True if arguments are desc */
  int nDist,                      /* Distance from left to right (1=adjacent) */
  char *aLeft, int nLeft,         /* Left doclist */
  char *aRight, int *pnRight      /* IN/OUT: Right/output doclist */
){
  sqlite3_int64 i1 = 0;
  sqlite3_int64 i2 = 0;
  sqlite3_int64 iPrev = 0;
  char *pEnd1 = &aLeft[nLeft];
  char *pEnd2 = &aRight[*pnRight];
  char *p1 = aLeft;
................................................................................
      fts3PoslistCopy(0, &p2);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescIdx, &i2);
    }
  }

  *pnRight = p - aOut;
}















































































/*
** Merge all doclists in the TermSelect.aaOutput[] array into a single
** doclist stored in TermSelect.aaOutput[0]. If successful, delete all
** other doclists (except the aaOutput[0] one) and return SQLITE_OK.
**
................................................................................
    if( pTS->aaOutput[i] ){
      if( !aOut ){
        aOut = pTS->aaOutput[i];
        nOut = pTS->anOutput[i];
        pTS->aaOutput[i] = 0;
      }else{
        int nNew;
        char *aNew;

        int rc = fts3DoclistOrMerge(p->bDescIdx, 
            pTS->aaOutput[i], pTS->anOutput[i], aOut, nOut, &aNew, &nNew
        );
        if( rc!=SQLITE_OK ){
          sqlite3_free(aOut);
          return rc;
................................................................................
    for(iOut=0; iOut<SizeofArray(pTS->aaOutput); iOut++){
      if( pTS->aaOutput[iOut]==0 ){
        assert( iOut>0 );
        pTS->aaOutput[iOut] = aMerge;
        pTS->anOutput[iOut] = nMerge;
        break;
      }else{
        char *aNew;
        int nNew;

        int rc = fts3DoclistOrMerge(p->bDescIdx, aMerge, nMerge, 
            pTS->aaOutput[iOut], pTS->anOutput[iOut], &aNew, &nNew
        );
        if( rc!=SQLITE_OK ){
          if( aMerge!=aDoclist ) sqlite3_free(aMerge);
................................................................................
){
  Fts3MultiSegReader *pSegcsr;   /* Object to allocate and return */
  int rc = SQLITE_NOMEM;          /* Return code */

  pSegcsr = sqlite3_malloc(sizeof(Fts3MultiSegReader));
  if( pSegcsr ){
    int i;

    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;
................................................................................

    if( bFound==0 ){
      rc = sqlite3Fts3SegReaderCursor(
          p, 0, FTS3_SEGCURSOR_ALL, zTerm, nTerm, isPrefix, 0, pSegcsr
      );
      pSegcsr->bLookup = !isPrefix;
    }




  }

  *ppSegcsr = pSegcsr;
  return rc;
}

static void fts3SegReaderCursorFree(Fts3MultiSegReader *pSegcsr){
................................................................................
    "ALTER TABLE %Q.'%q_segdir'   RENAME TO '%q_segdir';",
    p->zDb, p->zName, zName
  );
  return rc;
}

static int fts3SavepointMethod(sqlite3_vtab *pVtab, int iSavepoint){

  UNUSED_PARAMETER(iSavepoint);
  assert( ((Fts3Table *)pVtab)->inTransaction );
  assert( ((Fts3Table *)pVtab)->mxSavepoint < iSavepoint );
  TESTONLY( ((Fts3Table *)pVtab)->mxSavepoint = iSavepoint );
  return fts3SyncMethod(pVtab);
}
static int fts3ReleaseMethod(sqlite3_vtab *pVtab, int iSavepoint){
  TESTONLY( Fts3Table *p = (Fts3Table*)pVtab );
  UNUSED_PARAMETER(iSavepoint);
  UNUSED_PARAMETER(pVtab);
  assert( p->inTransaction );
................................................................................
  }else{
    sqlite3_free(aDoclist);
  }
  return rc;
}

static int fts3EvalDeferredPhrase(Fts3Cursor *pCsr, Fts3Phrase *pPhrase){

  int iToken;
  int rc = SQLITE_OK;

  int nMaxUndeferred = -1;
  char *aPoslist = 0;
  int nPoslist = 0;
  int iPrev = -1;
................................................................................
** 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.
*/
static int fts3EvalPhraseStart(Fts3Cursor *pCsr, int bOptOk, Fts3Phrase *p){
  int rc;

  Fts3PhraseToken *pFirst = &p->aToken[0];
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;

  assert( p->doclist.aAll==0 );

  if( pCsr->bDesc==pTab->bDescIdx && bOptOk==1 && p->nToken==1 
   && pFirst->pSegcsr && pFirst->pSegcsr->bLookup 
  ){
    /* Use the incremental approach. */
    int iCol = (p->iColumn >= pTab->nColumn ? -1 : p->iColumn);
    rc = sqlite3Fts3MsrIncrStart(
        pTab, pFirst->pSegcsr, iCol, pFirst->z, pFirst->n);
................................................................................
    }
  }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 */
    char *pEnd = &pDL->aAll[pDL->nAll];     /* 1 byte past end of aAll */
    if( pDL->pNextDocid ){
      pIter = pDL->pNextDocid;
    }else{
      pIter = pDL->aAll;
    }

    if( pIter>=pEnd ){
      /* We have already reached the end of this doclist. EOF. */
      *pbEof = 1;
    }else{
      sqlite3_int64 iDelta;
      pIter += sqlite3Fts3GetVarint(pIter, &iDelta);
      if( pTab->bDescIdx==0 || pDL->pNextDocid==0 ){
        pDL->iDocid += iDelta;
      }else{
        pDL->iDocid -= iDelta;
      }
      pDL->pList = pIter;
      fts3PoslistCopy(0, &pIter);
      pDL->nList = (pIter - pDL->pList);

      /* pIter now points just past the 0x00 that terminates the position-
      ** list for document pDL->iDocid. However, if this position-list was
      ** edited in place by fts3EvalNearTrim2(), then pIter may not actually
      ** point to the start of the next docid value. The following line deals
      ** with this case by advancing pIter past the zero-padding added by
      ** fts3EvalNearTrim2().  */
      while( pIter<pEnd && *pIter==0 ) pIter++;

      pDL->pNextDocid = pIter;
      assert( *pIter || pIter>=&pDL->aAll[pDL->nAll] );
      *pbEof = 0;
    }
  }

  return rc;
}

................................................................................
      fts3EvalStartReaders(pCsr, pExpr->pLeft, bOptOk, pRc);
      fts3EvalStartReaders(pCsr, pExpr->pRight, bOptOk, pRc);
      pExpr->bDeferred = (pExpr->pLeft->bDeferred && pExpr->pRight->bDeferred);
    }
  }
}






















































































typedef struct Fts3TokenAndCost Fts3TokenAndCost;
struct Fts3TokenAndCost {
  Fts3PhraseToken *pToken;
  Fts3Expr *pRoot;
  int nOvfl;
  int iCol;
................................................................................
      a += sqlite3Fts3GetVarint(a, &nByte);
    }
    if( nDoc==0 || nByte==0 ){
      sqlite3_reset(pStmt);
      return SQLITE_CORRUPT_VTAB;
    }

    pCsr->nDoc = nDoc;
    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;
................................................................................
    );
    apOr = (Fts3Expr **)&aTC[nToken];

    if( !aTC ){
      rc = SQLITE_NOMEM;
    }else{
      int ii;

      Fts3TokenAndCost *pTC = aTC;
      Fts3Expr **ppOr = apOr;

      fts3EvalTokenCosts(pCsr, 0, pExpr, &pTC, &ppOr, &rc);
      nToken = pTC-aTC;
      nOr = ppOr-apOr;

      if( rc==SQLITE_OK ){
        rc = fts3EvalSelectDeferred(pCsr, 0, aTC, nToken);
        for(ii=0; rc==SQLITE_OK && ii<nOr; ii++){
          rc = fts3EvalSelectDeferred(pCsr, apOr[ii], aTC, nToken);
        }
      }













































      sqlite3_free(aTC);
    }
  }

  fts3EvalStartReaders(pCsr, pExpr, bOptOk, &rc);
  return rc;
................................................................................
  char *aTmp,                     /* Temporary space to use */
  char **paPoslist,               /* IN/OUT: Position list */
  int *pnToken,                   /* IN/OUT: Tokens in phrase of *paPoslist */
  Fts3Phrase *pPhrase             /* The phrase object to trim the doclist of */
){
  int nParam1 = nNear + pPhrase->nToken;
  int nParam2 = nNear + *pnToken;
  int nNew;
  char *p2; 
  char *pOut; 
  int res;

  p2 = pOut = pPhrase->doclist.pList;
  res = fts3PoslistNearMerge(
    &pOut, aTmp, nParam1, nParam2, paPoslist, &p2
  );
  if( res ){
    nNew = (pOut - pPhrase->doclist.pList) - 1;
    assert( pPhrase->doclist.pList[nNew]=='\0' );
    assert( nNew<=pPhrase->doclist.nList && nNew>0 );
    memset(&pPhrase->doclist.pList[nNew], 0, pPhrase->doclist.nList - nNew);
    pPhrase->doclist.nList = nNew;
    *paPoslist = pPhrase->doclist.pList;
    *pnToken = pPhrase->nToken;
  }

  return res;
}

static int fts3EvalNearTest(Fts3Expr *pExpr, int *pRc){
  int res = 1;

................................................................................
      pCsr->isMatchinfoNeeded = 1;
      pCsr->iPrevId = pExpr->iDocid;
    }while( pCsr->isEof==0 && fts3EvalLoadDeferred(pCsr, &rc) );
  }
  return rc;
}

static void fts3EvalRestart(
  Fts3Cursor *pCsr,
  Fts3Expr *pExpr,
  int *pRc
){
  if( pExpr && *pRc==SQLITE_OK ){
    Fts3Phrase *pPhrase = pExpr->pPhrase;

    if( pPhrase ){
      fts3EvalFreeDeferredDoclist(pPhrase);
      if( pPhrase->bIncr ){
        sqlite3Fts3EvalPhraseCleanup(pPhrase);
        memset(&pPhrase->doclist, 0, sizeof(Fts3Doclist));
        *pRc = sqlite3Fts3EvalStart(pCsr, pExpr, 0);
      }else{
        pPhrase->doclist.pNextDocid = 0;
        pPhrase->doclist.iDocid = 0;
      }
    }

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

    fts3EvalRestart(pCsr, pExpr->pLeft, pRc);
    fts3EvalRestart(pCsr, pExpr->pRight, pRc);
  }
}

static void fts3EvalUpdateCounts(
  Fts3Cursor *pCsr,
  Fts3Expr *pExpr,
  int *pRc
){
  if( pExpr && *pRc==SQLITE_OK ){
    Fts3Phrase *pPhrase = pExpr->pPhrase;
    if( pPhrase && pPhrase->doclist.pList ){
      int iCol = 0;
      char *p = pPhrase->doclist.pList;

      assert( *p );
      while( 1 ){
        u8 c = 0;
        int iCnt = 0;
        while( 0xFE & (*p | c) ){
          if( (c&0x80)==0 ) iCnt++;
          c = *p++ & 0x80;
        }

        /* aMI[iCol*3 + 1] = Number of occurrences
        ** aMI[iCol*3 + 2] = Number of rows containing at least one instance
        */
        pExpr->aMI[iCol*3 + 1] += iCnt;
        pExpr->aMI[iCol*3 + 2] += (iCnt>0);
        if( *p==0x00 ) break;
        p++;
        p += sqlite3Fts3GetVarint32(p, &iCol);
      }
    }

    fts3EvalUpdateCounts(pCsr, pExpr->pLeft, pRc);
    fts3EvalUpdateCounts(pCsr, pExpr->pRight, pRc);
  }
}

static int fts3EvalNearStats(
  Fts3Cursor *pCsr,
  Fts3Expr *pExpr
){
  int rc = SQLITE_OK;             /* Return code */

  assert( pExpr->eType==FTSQUERY_PHRASE );
  if( pExpr->aMI==0 ){
    Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
    Fts3Expr *pRoot;                /* Root of NEAR expression */
    Fts3Expr *p;                    /* Iterator used for several purposes */

    sqlite3_int64 iPrevId = pCsr->iPrevId;
    sqlite3_int64 iDocid;
    u8 bEof;

    /* Find the root of the NEAR expression */
    pRoot = pExpr;
    while( pRoot->pParent && pRoot->pParent->eType==FTSQUERY_NEAR ){
      pRoot = pRoot->pParent;
    }
    iDocid = pRoot->iDocid;
    bEof = pRoot->bEof;

    /* Allocate space for the aMSI[] array of each FTSQUERY_PHRASE node */
    for(p=pRoot; p; p=p->pLeft){
      Fts3Expr *pE = (p->eType==FTSQUERY_PHRASE?p:p->pRight);
      assert( pE->aMI==0 );
      pE->aMI = (u32 *)sqlite3_malloc(pTab->nColumn * 3 * sizeof(u32));
      if( !pE->aMI ) return SQLITE_NOMEM;
      memset(pE->aMI, 0, pTab->nColumn * 3 * sizeof(u32));
    }

    fts3EvalRestart(pCsr, pRoot, &rc);

    while( pCsr->isEof==0 && rc==SQLITE_OK ){

      do {
        /* Ensure the %_content statement is reset. */
        if( pCsr->isRequireSeek==0 ) sqlite3_reset(pCsr->pStmt);
        assert( sqlite3_data_count(pCsr->pStmt)==0 );

        /* Advance to the next document */
        fts3EvalNext(pCsr, pRoot, &rc);
        pCsr->isEof = pRoot->bEof;
        pCsr->isRequireSeek = 1;
        pCsr->isMatchinfoNeeded = 1;
        pCsr->iPrevId = pRoot->iDocid;
      }while( pCsr->isEof==0 
           && pRoot->eType==FTSQUERY_NEAR 
           && fts3EvalLoadDeferred(pCsr, &rc) 
      );

      if( pCsr->isEof==0 ){
        fts3EvalUpdateCounts(pCsr, pRoot, &rc);
      }
    }

    pCsr->isEof = 0;
    pCsr->iPrevId = iPrevId;

    if( bEof ){
      pRoot->bEof = bEof;
    }else{
      fts3EvalRestart(pCsr, pRoot, &rc);
      while( pRoot->iDocid<iDocid && rc==SQLITE_OK ){
        fts3EvalNext(pCsr, pRoot, &rc);
        assert( pRoot->bEof==0 );
      }
      fts3EvalLoadDeferred(pCsr, &rc);
    }
  }
  return rc;
}

/*



** This function is used by the matchinfo() module to query a phrase 
** expression node for the following information:
**


**   1. The total number of occurrences of the phrase in each column of 
**      the FTS table (considering all rows), and
**


**   2. For each column, the number of rows in the table for which the
**      column contains at least one instance of the phrase.
**


** If no error occurs, SQLITE_OK is returned and the values for each column
** written into the array aiOut as follows:
**




**   aiOut[iCol*3 + 1] = Number of occurrences
**   aiOut[iCol*3 + 2] = Number of rows containing at least one instance
**
** Caveats:
**
**   * If a phrase consists entirely of deferred tokens, then all output 
**     values are set to the number of documents in the table. In other
**     words we assume that very common tokens occur exactly once in each 
**     column of each row of the table.
**
**   * If a phrase contains some deferred tokens (and some non-deferred 
**     tokens), count the potential occurrence identified by considering
**     the non-deferred tokens instead of actual phrase occurrences.
**
**   * If the phrase is part of a NEAR expression, then only phrase instances
**     that meet the NEAR constraint are included in the counts.
*/
int sqlite3Fts3EvalPhraseStats(
  Fts3Cursor *pCsr,               /* FTS cursor handle */
  Fts3Expr *pExpr,                /* Phrase expression */


  u32 *aiOut                      /* Array to write results into (see above) */
){
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
  int rc = SQLITE_OK;

  int iCol;





  if( pExpr->bDeferred ){
    assert( pCsr->nDoc>0 );
    for(iCol=0; iCol<pTab->nColumn; iCol++){
      aiOut[iCol*3 + 1] = pCsr->nDoc;
      aiOut[iCol*3 + 2] = pCsr->nDoc;
    }




















  }else{
    rc = fts3EvalNearStats(pCsr, pExpr);
    if( rc==SQLITE_OK ){
      assert( pExpr->aMI );
      for(iCol=0; iCol<pTab->nColumn; iCol++){
        aiOut[iCol*3 + 1] = pExpr->aMI[iCol*3 + 1];
        aiOut[iCol*3 + 2] = pExpr->aMI[iCol*3 + 2];
      }
    }
  }










  return rc;
}

/*
** The expression pExpr passed as the second argument to this function
** must be of type FTSQUERY_PHRASE. 
**

  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 */
  u8 bDesc;                       /* True to sort in descending order */
  int eEvalmode;                  /* An FTS3_EVAL_XX constant */
  int nRowAvg;                    /* Average size of database rows, in pages */


  int isMatchinfoNeeded;          /* True when aMatchinfo[] needs filling in */
  u32 *aMatchinfo;                /* Information about most recent match */
  int nMatchinfo;                 /* Number of elements in aMatchinfo[] */
  char *zMatchinfo;               /* Matchinfo specification */
};

................................................................................
**
** If Fts3Expr.eType is FTSQUERY_PHRASE and isLoaded is true, then aDoclist 
** points to a malloced buffer, size nDoclist bytes, containing the results 
** of this phrase query in FTS3 doclist format. As usual, the initial 
** "Length" field found in doclists stored on disk is omitted from this 
** buffer.
**
** Variable pCurrent always points to the start of a docid field within
** aDoclist. Since the doclist is usually scanned in docid order, this can
** be used to accelerate seeking to the required docid within the doclist.








*/
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:
**
................................................................................
void sqlite3Fts3PendingTermsClear(Fts3Table *);
int sqlite3Fts3Optimize(Fts3Table *);
int sqlite3Fts3SegReaderNew(int, sqlite3_int64,
  sqlite3_int64, sqlite3_int64, const char *, int, Fts3SegReader**);
int sqlite3Fts3SegReaderPending(
  Fts3Table*,int,const char*,int,int,Fts3SegReader**);
void sqlite3Fts3SegReaderFree(Fts3SegReader *);
int sqlite3Fts3SegReaderCost(Fts3Cursor *, Fts3SegReader *, int *);
int sqlite3Fts3AllSegdirs(Fts3Table*, int, int, sqlite3_stmt **);
int sqlite3Fts3ReadLock(Fts3Table *);
int sqlite3Fts3ReadBlock(Fts3Table*, sqlite3_int64, char **, int*, int*);

int sqlite3Fts3SelectDoctotal(Fts3Table *, sqlite3_stmt **);
int sqlite3Fts3SelectDocsize(Fts3Table *, sqlite3_int64, sqlite3_stmt **);

void sqlite3Fts3FreeDeferredTokens(Fts3Cursor *);
int sqlite3Fts3DeferToken(Fts3Cursor *, Fts3PhraseToken *, int);
int sqlite3Fts3CacheDeferredDoclists(Fts3Cursor *);
void sqlite3Fts3FreeDeferredDoclists(Fts3Cursor *);
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 sqlite3Fts3PutVarint(char *, sqlite3_int64);
int sqlite3Fts3GetVarint(const char *, sqlite_int64 *);
int sqlite3Fts3GetVarint32(const char *, int *);
int sqlite3Fts3VarintLen(sqlite3_uint64);
void sqlite3Fts3Dequote(char *);
void sqlite3Fts3DoclistPrev(int,char*,int,char**,sqlite3_int64*,int*,u8*);

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

/* fts3_tokenizer.c */
const char *sqlite3Fts3NextToken(const char *, int *);
int sqlite3Fts3InitHashTable(sqlite3 *, Fts3Hash *, const char *);
int sqlite3Fts3InitTokenizer(Fts3Hash *pHash, const char *, 
    sqlite3_tokenizer **, char **
);
................................................................................
  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);

int sqlite3Fts3MsrIncrStart(
    Fts3Table*, Fts3MultiSegReader*, int, const char*, int);

  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 */
  u8 bDesc;                       /* True to sort in descending order */
  int eEvalmode;                  /* An FTS3_EVAL_XX constant */
  int nRowAvg;                    /* Average size of database rows, in pages */
  int nDoc;                       /* Documents in table */

  int isMatchinfoNeeded;          /* True when aMatchinfo[] needs filling in */
  u32 *aMatchinfo;                /* Information about most recent match */
  int nMatchinfo;                 /* Number of elements in aMatchinfo[] */
  char *zMatchinfo;               /* Matchinfo specification */
};

................................................................................
**
** If Fts3Expr.eType is FTSQUERY_PHRASE and isLoaded is true, then aDoclist 
** points to a malloced buffer, size nDoclist bytes, containing the results 
** of this phrase query in FTS3 doclist format. As usual, the initial 
** "Length" field found in doclists stored on disk is omitted from this 
** buffer.
**
** Variable aMI is used only for FTSQUERY_NEAR nodes to store the global
** matchinfo data. If it is not NULL, it points to an array of size nCol*3,
** where nCol is the number of columns in the queried FTS table. The array
** is populated as follows:
**
**   aMI[iCol*3 + 0] = Undefined
**   aMI[iCol*3 + 1] = Number of occurrences
**   aMI[iCol*3 + 2] = Number of rows containing at least one instance
**
** The aMI array is allocated using sqlite3_malloc(). It should be freed 
** when the expression node is.
*/
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 */

  u32 *aMI;
};

/*
** 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:
**
................................................................................
void sqlite3Fts3PendingTermsClear(Fts3Table *);
int sqlite3Fts3Optimize(Fts3Table *);
int sqlite3Fts3SegReaderNew(int, sqlite3_int64,
  sqlite3_int64, sqlite3_int64, const char *, int, Fts3SegReader**);
int sqlite3Fts3SegReaderPending(
  Fts3Table*,int,const char*,int,int,Fts3SegReader**);
void sqlite3Fts3SegReaderFree(Fts3SegReader *);

int sqlite3Fts3AllSegdirs(Fts3Table*, int, int, sqlite3_stmt **);
int sqlite3Fts3ReadLock(Fts3Table *);
int sqlite3Fts3ReadBlock(Fts3Table*, sqlite3_int64, char **, int*, int*);

int sqlite3Fts3SelectDoctotal(Fts3Table *, sqlite3_stmt **);
int sqlite3Fts3SelectDocsize(Fts3Table *, sqlite3_int64, sqlite3_stmt **);

void sqlite3Fts3FreeDeferredTokens(Fts3Cursor *);
int sqlite3Fts3DeferToken(Fts3Cursor *, Fts3PhraseToken *, int);
int sqlite3Fts3CacheDeferredDoclists(Fts3Cursor *);
void sqlite3Fts3FreeDeferredDoclists(Fts3Cursor *);

void sqlite3Fts3SegmentsClose(Fts3Table *);

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

int sqlite3Fts3SegReaderStart(Fts3Table*, Fts3MultiSegReader*, Fts3SegFilter*);
................................................................................
int sqlite3Fts3PutVarint(char *, sqlite3_int64);
int sqlite3Fts3GetVarint(const char *, sqlite_int64 *);
int sqlite3Fts3GetVarint32(const char *, int *);
int sqlite3Fts3VarintLen(sqlite3_uint64);
void sqlite3Fts3Dequote(char *);
void sqlite3Fts3DoclistPrev(int,char*,int,char**,sqlite3_int64*,int*,u8*);

int sqlite3Fts3EvalPhraseStats(Fts3Cursor *, Fts3Expr *, u32 *);


/* fts3_tokenizer.c */
const char *sqlite3Fts3NextToken(const char *, int *);
int sqlite3Fts3InitHashTable(sqlite3 *, Fts3Hash *, const char *);
int sqlite3Fts3InitTokenizer(Fts3Hash *pHash, const char *, 
    sqlite3_tokenizer **, char **
);
................................................................................
  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 */
);




void sqlite3Fts3EvalPhraseCleanup(Fts3Phrase *);

int sqlite3Fts3EvalStart(Fts3Cursor *, Fts3Expr *, int);
int sqlite3Fts3EvalNext(Fts3Cursor *pCsr);

int sqlite3Fts3MsrIncrStart(
    Fts3Table*, Fts3MultiSegReader*, int, const char*, int);

*/
void sqlite3Fts3ExprFree(Fts3Expr *p){
  if( p ){
    assert( p->eType==FTSQUERY_PHRASE || p->pPhrase==0 );
    sqlite3Fts3ExprFree(p->pLeft);
    sqlite3Fts3ExprFree(p->pRight);
    sqlite3Fts3EvalPhraseCleanup(p->pPhrase);

    sqlite3_free(p);
  }
}

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

*/
void sqlite3Fts3ExprFree(Fts3Expr *p){
  if( p ){
    assert( p->eType==FTSQUERY_PHRASE || p->pPhrase==0 );
    sqlite3Fts3ExprFree(p->pLeft);
    sqlite3Fts3ExprFree(p->pRight);
    sqlite3Fts3EvalPhraseCleanup(p->pPhrase);
    sqlite3_free(p->aMI);
    sqlite3_free(p);
  }
}

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

    if( !c ) nEntry++;
  }

  *ppCollist = pEnd;
  return nEntry;
}

static void fts3LoadColumnlistCounts(char **pp, u32 *aOut, int isGlobal){
  char *pCsr = *pp;
  while( *pCsr ){
    int nHit;
    sqlite3_int64 iCol = 0;
    if( *pCsr==0x01 ){
      pCsr++;
      pCsr += sqlite3Fts3GetVarint(pCsr, &iCol);
    }
    nHit = fts3ColumnlistCount(&pCsr);
    assert( nHit>0 );
    if( isGlobal ){
      aOut[iCol*3+1]++;
    }
    aOut[iCol*3] += nHit;
  }
  pCsr++;
  *pp = pCsr;
}

/*
** fts3ExprIterate() callback used to collect the "global" matchinfo stats
** for a single query. 
**
** fts3ExprIterate() callback to load the 'global' elements of a
** FTS3_MATCHINFO_HITS matchinfo array. The global stats are those elements 
** of the matchinfo array that are constant for all rows returned by the 
................................................................................
*/
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.
*/

    if( !c ) nEntry++;
  }

  *ppCollist = pEnd;
  return nEntry;
}





















/*
** fts3ExprIterate() callback used to collect the "global" matchinfo stats
** for a single query. 
**
** fts3ExprIterate() callback to load the 'global' elements of a
** FTS3_MATCHINFO_HITS matchinfo array. The global stats are those elements 
** of the matchinfo array that are constant for all rows returned by the 
................................................................................
*/
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;












  return sqlite3Fts3EvalPhraseStats(
      p->pCursor, pExpr, &p->aMatchinfo[3*iPhrase*p->nCol]
  );











}

/*
** 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.
*/

** a contiguous set of segment b-tree leaf nodes. Although the details of
** this structure are only manipulated by code in this file, opaque handles
** of type Fts3SegReader* are also used by code in fts3.c to iterate through
** terms when querying the full-text index. See functions:
**
**   sqlite3Fts3SegReaderNew()
**   sqlite3Fts3SegReaderFree()
**   sqlite3Fts3SegReaderCost()
**   sqlite3Fts3SegReaderIterate()
**
** Methods used to manipulate Fts3SegReader structures:
**
**   fts3SegReaderNext()
**   fts3SegReaderFirstDocid()
**   fts3SegReaderNextDocid()
................................................................................
      }
    }
  }

  return SQLITE_OK;
}

/*
** This function is called to estimate the amount of data that will be 
** loaded from the disk If SegReaderIterate() is called on this seg-reader,
** in units of average document size.
** 
** This can be used as follows: If the caller has a small doclist that 
** contains references to N documents, and is considering merging it with
** a large doclist (size X "average documents"), it may opt not to load
** the large doclist if X>N.
*/
int sqlite3Fts3SegReaderCost(
  Fts3Cursor *pCsr,               /* FTS3 cursor handle */
  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) 
   && !fts3SegReaderIsRootOnly(pReader) 
  ){
    int nBlob = 0;
    sqlite3_int64 iBlock;

    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.
      */
      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) + pgsz) / pgsz);
      assert( pCsr->nRowAvg>0 ); 
      rc = sqlite3_reset(pStmt);
      if( rc!=SQLITE_OK ) return rc;
    }

    /* Assume that a blob flows over onto overflow pages if it is larger
    ** than (pgsz-35) bytes in size (the file-format documentation
    ** confirms this).
    */
    for(iBlock=pReader->iStartBlock; iBlock<=pReader->iLeafEndBlock; iBlock++){
      rc = sqlite3Fts3ReadBlock(p, iBlock, 0, &nBlob, 0);
      if( rc!=SQLITE_OK ) break;
      if( (nBlob+35)>pgsz ){
        int nOvfl = (nBlob + 34)/pgsz;
        nCost += ((nOvfl + pCsr->nRowAvg - 1)/pCsr->nRowAvg);
      }
    }
  }

  *pnCost += nCost;
  return rc;
}

int sqlite3Fts3MsrOvfl(
  Fts3Cursor *pCsr, 
  Fts3MultiSegReader *pMsr,
  int *pnOvfl
){
  Fts3Table *p = (Fts3Table*)pCsr->base.pVtab;
................................................................................

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

  while( 1 ){
    int nSort;
    Fts3SegReader *pSeg;
    pSeg = pMsr->apSegment[0];

    if( pSeg->pOffsetList==0 ){
      *paPoslist = 0;
      break;
    }else{
................................................................................
  }else{
    rc = SQLITE_ERROR;
  }

  return rc;
}

/*
** Return the deferred doclist associated with deferred token pDeferred.
** This function assumes that sqlite3Fts3CacheDeferredDoclists() has already
** been called to allocate and populate the doclist.
*/
char *sqlite3Fts3DeferredDoclist(Fts3DeferredToken *pDeferred, int *pnByte){
  if( pDeferred->pList ){
    *pnByte = pDeferred->pList->nData;
    return pDeferred->pList->aData;
  }
  *pnByte = 0;
  return 0;
}

/*
** Delete all cached deferred doclists. Deferred doclists are cached
** (allocated) by the sqlite3Fts3CacheDeferredDoclists() function.
*/
void sqlite3Fts3FreeDeferredDoclists(Fts3Cursor *pCsr){
  Fts3DeferredToken *pDef;
  for(pDef=pCsr->pDeferred; pDef; pDef=pDef->pNext){

** a contiguous set of segment b-tree leaf nodes. Although the details of
** this structure are only manipulated by code in this file, opaque handles
** of type Fts3SegReader* are also used by code in fts3.c to iterate through
** terms when querying the full-text index. See functions:
**
**   sqlite3Fts3SegReaderNew()
**   sqlite3Fts3SegReaderFree()

**   sqlite3Fts3SegReaderIterate()
**
** Methods used to manipulate Fts3SegReader structures:
**
**   fts3SegReaderNext()
**   fts3SegReaderFirstDocid()
**   fts3SegReaderNextDocid()
................................................................................
      }
    }
  }

  return SQLITE_OK;
}



























































































int sqlite3Fts3MsrOvfl(
  Fts3Cursor *pCsr, 
  Fts3MultiSegReader *pMsr,
  int *pnOvfl
){
  Fts3Table *p = (Fts3Table*)pCsr->base.pVtab;
................................................................................

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

  while( 1 ){

    Fts3SegReader *pSeg;
    pSeg = pMsr->apSegment[0];

    if( pSeg->pOffsetList==0 ){
      *paPoslist = 0;
      break;
    }else{
................................................................................
  }else{
    rc = SQLITE_ERROR;
  }

  return rc;
}















/*
** Delete all cached deferred doclists. Deferred doclists are cached
** (allocated) by the sqlite3Fts3CacheDeferredDoclists() function.
*/
void sqlite3Fts3FreeDeferredDoclists(Fts3Cursor *pCsr){
  Fts3DeferredToken *pDef;
  for(pDef=pCsr->pDeferred; pDef; pDef=pDef->pNext){

do_matchinfo_test 4.2.3 t5 {t5 MATCH 'a b a'}       { s {3} }
do_matchinfo_test 4.2.4 t5 {t5 MATCH 'a a a'}       { s {3 1} }
do_matchinfo_test 4.2.5 t5 {t5 MATCH '"a b" "a b"'} { s {2} }
do_matchinfo_test 4.2.6 t5 {t5 MATCH 'a OR b'}      { s {1 2 1} }

do_execsql_test 4.3.0 "INSERT INTO t5 VALUES('x y [string repeat {b } 50000]')";




do_matchinfo_test 4.3.1 t5 {t5 MATCH 'a a'} { 
  x {{5 8 2   5 5 5} {3 8 2   3 5 5}}
  s {2 1} 

}

do_matchinfo_test 4.3.2 t5 {t5 MATCH 'a b'}         { s {2} }
do_matchinfo_test 4.3.3 t5 {t5 MATCH 'a b a'}       { s {3} }
do_matchinfo_test 4.3.4 t5 {t5 MATCH 'a a a'}       { s {3 1} }
do_matchinfo_test 4.3.5 t5 {t5 MATCH '"a b" "a b"'} { s {2} }
do_matchinfo_test 4.3.6 t5 {t5 MATCH 'a OR b'}      { s {1 2 1 1} }

do_matchinfo_test 4.2.3 t5 {t5 MATCH 'a b a'}       { s {3} }
do_matchinfo_test 4.2.4 t5 {t5 MATCH 'a a a'}       { s {3 1} }
do_matchinfo_test 4.2.5 t5 {t5 MATCH '"a b" "a b"'} { s {2} }
do_matchinfo_test 4.2.6 t5 {t5 MATCH 'a OR b'}      { s {1 2 1} }

do_execsql_test 4.3.0 "INSERT INTO t5 VALUES('x y [string repeat {b } 50000]')";

# It used to be that the second 'a' token would be deferred. That doesn't
# work any longer.
if 0 {
  do_matchinfo_test 4.3.1 t5 {t5 MATCH 'a a'} { 
    x {{5 8 2   5 5 5} {3 8 2   3 5 5}}
    s {2 1} 
  }
}

do_matchinfo_test 4.3.2 t5 {t5 MATCH 'a b'}         { s {2} }
do_matchinfo_test 4.3.3 t5 {t5 MATCH 'a b a'}       { s {3} }
do_matchinfo_test 4.3.4 t5 {t5 MATCH 'a a a'}       { s {3 1} }
do_matchinfo_test 4.3.5 t5 {t5 MATCH '"a b" "a b"'} { s {2} }
do_matchinfo_test 4.3.6 t5 {t5 MATCH 'a OR b'}      { s {1 2 1 1} }