SQLite

**
** If the docids in the input doclists are sorted in ascending order,
** parameter bDescDoclist should be false. If they are sorted in ascending 
** order, it should be passed a non-zero value.
**
** The right-hand input doclist is overwritten by this function.
*/
static int fts3DoclistPhraseMerge(
  int bDescDoclist,               /* True if arguments are desc */
  int nDist,                      /* Distance from left to right (1=adjacent) */
  char *aLeft, int nLeft,         /* Left doclist */
  char **paRight, int *pnRight    /* IN/OUT: Right/output doclist */
){
  sqlite3_int64 i1 = 0;
  sqlite3_int64 i2 = 0;
  sqlite3_int64 iPrev = 0;
  char *aRight = *paRight;
  char *pEnd1 = &aLeft[nLeft];
  char *pEnd2 = &aRight[*pnRight];
  char *p1 = aLeft;
  char *p2 = aRight;
  char *p;
  int bFirstOut = 0;
  char *aOut;

  assert( nDist>0 );
  if( bDescDoclist ){
    aOut = sqlite3_malloc(*pnRight + FTS3_VARINT_MAX);
    if( aOut==0 ) return SQLITE_NOMEM;
  }else{
    aOut = aRight;
  }
  p = aOut;

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

  while( p1 && p2 ){
    sqlite3_int64 iDiff = DOCID_CMP(i1, i2);
    if( iDiff==0 ){
      char *pSave = p;

    }else{
      fts3PoslistCopy(0, &p2);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescDoclist, &i2);
    }
  }

  *pnRight = (int)(p - aOut);
  if( bDescDoclist ){
    sqlite3_free(aRight);
    *paRight = aOut;
  }

  return SQLITE_OK;
}

/*
** Argument pList points to a position list nList bytes in size. This
** function checks to see if the position list contains any entries for
** a token in position 0 (of any column). If so, it writes argument iDelta
** to the output buffer pOut, followed by a position list consisting only

  Fts3Table *p,                   /* FTS table handle */
  TermSelect *pTS,                /* TermSelect object to merge into */
  char *aDoclist,                 /* Pointer to doclist */
  int nDoclist                    /* Size of aDoclist in bytes */
){
  if( pTS->aaOutput[0]==0 ){
    /* If this is the first term selected, copy the doclist to the output
    ** buffer using memcpy(). 
    **
    ** Add FTS3_VARINT_MAX bytes of unused space to the end of the 
    ** allocation. This is so as to ensure that the buffer is big enough
    ** to hold the current doclist AND'd with any other doclist. If the
    ** doclists are stored in order=ASC order, this padding would not be
    ** required (since the size of [doclistA AND doclistB] is always less
    ** than or equal to the size of [doclistA] in that case). But this is
    ** not true for order=DESC. For example, a doclist containing (1, -1) 
    ** may be smaller than (-1), as in the first example the -1 may be stored
    ** as a single-byte delta, whereas in the second it must be stored as a
    ** FTS3_VARINT_MAX byte varint.
    **
    ** Similar padding is added in the fts3DoclistOrMerge() function.
    */
    pTS->aaOutput[0] = sqlite3_malloc(nDoclist + FTS3_VARINT_MAX + 1);
    pTS->anOutput[0] = nDoclist;
    if( pTS->aaOutput[0] ){
      memcpy(pTS->aaOutput[0], aDoclist, nDoclist);
    }else{
      return SQLITE_NOMEM;
    }
  }else{

/*
** Arguments pList/nList contain the doclist for token iToken of phrase p.
** It is merged into the main doclist stored in p->doclist.aAll/nAll.
**
** This function assumes that pList points to a buffer allocated using
** sqlite3_malloc(). This function takes responsibility for eventually
** freeing the buffer.
**
** SQLITE_OK is returned if successful, or SQLITE_NOMEM if an error occurs.
*/
static int fts3EvalPhraseMergeToken(
  Fts3Table *pTab,                /* FTS Table pointer */
  Fts3Phrase *p,                  /* Phrase to merge pList/nList into */
  int iToken,                     /* Token pList/nList corresponds to */
  char *pList,                    /* Pointer to doclist */
  int nList                       /* Number of bytes in pList */
){
  int rc = SQLITE_OK;
  assert( iToken!=p->iDoclistToken );

  if( pList==0 ){
    sqlite3_free(p->doclist.aAll);
    p->doclist.aAll = 0;
    p->doclist.nAll = 0;
  }

      pRight = p->doclist.aAll;
      nRight = p->doclist.nAll;
      pLeft = pList;
      nLeft = nList;
      nDiff = p->iDoclistToken - iToken;
    }

    rc = fts3DoclistPhraseMerge(
        pTab->bDescIdx, nDiff, pLeft, nLeft, &pRight, &nRight
    );
    sqlite3_free(pLeft);
    p->doclist.aAll = pRight;
    p->doclist.nAll = nRight;
  }

  if( iToken>p->iDoclistToken ) p->iDoclistToken = iToken;
  return rc;
}

/*
** Load the doclist for phrase p into p->doclist.aAll/nAll. The loaded doclist
** does not take deferred tokens into account.
**
** SQLITE_OK is returned if no error occurs, otherwise an SQLite error code.

    assert( pToken->pDeferred==0 || pToken->pSegcsr==0 );

    if( pToken->pSegcsr ){
      int nThis = 0;
      char *pThis = 0;
      rc = fts3TermSelect(pTab, pToken, p->iColumn, &nThis, &pThis);
      if( rc==SQLITE_OK ){
        rc = fts3EvalPhraseMergeToken(pTab, p, iToken, pThis, nThis);
      }
    }
    assert( pToken->pSegcsr==0 );
  }

  return rc;
}

        ** part of a multi-token phrase. Either way, the entire doclist will
        ** (eventually) be loaded into memory. It may as well be now. */
        Fts3PhraseToken *pToken = pTC->pToken;
        int nList = 0;
        char *pList = 0;
        rc = fts3TermSelect(pTab, pToken, pTC->iCol, &nList, &pList);
        assert( rc==SQLITE_OK || pList==0 );
        if( rc==SQLITE_OK ){
          rc = fts3EvalPhraseMergeToken(
              pTab, pTC->pPhrase, pTC->iToken,pList,nList
          );
        }
        if( rc==SQLITE_OK ){
          int nCount;

          nCount = fts3DoclistCountDocids(
              pTC->pPhrase->doclist.aAll, pTC->pPhrase->doclist.nAll
          );
          if( ii==0 || nCount<nMinEst ) nMinEst = nCount;
        }
      }
    }

  CREATE VIRTUAL TABLE t2 USING fts4(prefix=);
  INSERT INTO t1 VALUES('He dressed himself in cycling clothes');
  INSERT INTO t2 VALUES('He dressed himself in cycling clothes');
} {}
do_execsql_test 6.5.2 {
  SELECT md5sum(quote(root)) FROM t1_segdir;
} [db eval {SELECT md5sum(quote(root)) FROM t2_segdir}]


do_execsql_test 7.0 {
  CREATE VIRTUAL TABLE t6 USING fts4(x,order=DESC);
  INSERT INTO t6(docid, x) VALUES(-1,'a b');
  INSERT INTO t6(docid, x) VALUES(1, 'b');
}
do_execsql_test 7.1 {
  SELECT docid FROM t6 WHERE t6 MATCH '"a* b"';
} {-1}
do_execsql_test 7.2 {
  SELECT docid FROM t6 WHERE t6 MATCH 'a*';
} {-1}
do_execsql_test 7.3 {
  SELECT docid FROM t6 WHERE t6 MATCH 'a* b';
} {-1}



finish_test