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Overview
Comment:Fix a performance problem in queries that use "ORDER BY rowid DESC" and one or more FTS auxiliary functions.
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SHA1: 95e09b20e9aad28f829c8950f3632debe473070a
User & Date: dan 2011-05-04 15:41:18
Context
2011-05-04
16:30
Fix a couple of compiler warnings in the FTS code. Closed-Leaf check-in: 1a113359 user: dan tags: vtab-conflict
15:41
Fix a performance problem in queries that use "ORDER BY rowid DESC" and one or more FTS auxiliary functions. check-in: 95e09b20 user: dan tags: vtab-conflict
12:52
Optimize "ORDER BY rowid/docid DESC/ASC" clauses on FTS tables. check-in: 13395121 user: dan tags: vtab-conflict
Changes
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Changes to ext/fts3/fts3.c.

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  assert( pCsr->eEvalmode==FTS3_EVAL_NEXT );
  assert( pExpr->eType==FTSQUERY_PHRASE && pExpr->pPhrase );
  pCsr->eEvalmode = FTS3_EVAL_MATCHINFO;
  rc = fts3EvalExpr(pCsr, pExpr, paDoclist, pnDoclist, 1);
  pCsr->eEvalmode = FTS3_EVAL_NEXT;
  return rc;
}




















/*
** After ExprLoadDoclist() (see above) has been called, this function is
** used to iterate/search through the position lists that make up the doclist
** stored in pExpr->aDoclist.
*/
char *sqlite3Fts3FindPositions(
................................................................................
  int iCol                        /* Column of requested pos-list */
){
  assert( pExpr->isLoaded );
  if( pExpr->aDoclist ){
    char *pEnd = &pExpr->aDoclist[pExpr->nDoclist];
    char *pCsr;

    if( pExpr->pCurrent==0 || pCursor->desc ){

      pExpr->pCurrent = pExpr->aDoclist;
      pExpr->iCurrent = 0;
      pExpr->pCurrent += sqlite3Fts3GetVarint(pExpr->pCurrent,&pExpr->iCurrent);










    }
    pCsr = pExpr->pCurrent;
    assert( pCsr );

    while( pCsr<pEnd ){


      if( pExpr->iCurrent<iDocid ){
        fts3PoslistCopy(0, &pCsr);
        if( pCsr<pEnd ){
          fts3GetDeltaVarint(&pCsr, &pExpr->iCurrent);
        }




        pExpr->pCurrent = pCsr;
      }else{
        if( pExpr->iCurrent==iDocid ){
          int iThis = 0;
          if( iCol<0 ){
            /* If iCol is negative, return a pointer to the start of the
            ** position-list (instead of a pointer to the start of a list







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  assert( pCsr->eEvalmode==FTS3_EVAL_NEXT );
  assert( pExpr->eType==FTSQUERY_PHRASE && pExpr->pPhrase );
  pCsr->eEvalmode = FTS3_EVAL_MATCHINFO;
  rc = fts3EvalExpr(pCsr, pExpr, paDoclist, pnDoclist, 1);
  pCsr->eEvalmode = FTS3_EVAL_NEXT;
  return rc;
}


/*
** When called, *ppPoslist must point to the byte immediately following the
** end of a position-list. i.e. ( (*ppPoslist)[-1]==POS_END ). This function
** moves *ppPoslist so that it instead points to the first byte of the
** position list.
*/
static void fts3ReversePoslist(char *pStart, char **ppPoslist){
  char *p = &(*ppPoslist)[-3];
  char c = p[1];
  while( p>=pStart && (*p & 0x80) | c ){ 
    c = *p--; 
  }
  if( p>pStart ){ p = &p[2]; }
  while( *p++&0x80 );
  *ppPoslist = p;
}


/*
** After ExprLoadDoclist() (see above) has been called, this function is
** used to iterate/search through the position lists that make up the doclist
** stored in pExpr->aDoclist.
*/
char *sqlite3Fts3FindPositions(
................................................................................
  int iCol                        /* Column of requested pos-list */
){
  assert( pExpr->isLoaded );
  if( pExpr->aDoclist ){
    char *pEnd = &pExpr->aDoclist[pExpr->nDoclist];
    char *pCsr;

    if( pExpr->pCurrent==0 ){
      if( pCursor->desc==0 ){
        pExpr->pCurrent = pExpr->aDoclist;
        pExpr->iCurrent = 0;

        fts3GetDeltaVarint(&pExpr->pCurrent, &pExpr->iCurrent);
      }else{
        pCsr = pExpr->aDoclist;
        while( pCsr<pEnd ){
          fts3GetDeltaVarint(&pCsr, &pExpr->iCurrent);
          fts3PoslistCopy(0, &pCsr);
        }
        fts3ReversePoslist(pExpr->aDoclist, &pCsr);
        pExpr->pCurrent = pCsr;
      }
    }
    pCsr = pExpr->pCurrent;
    assert( pCsr );

    while( (pCursor->desc==0 && pCsr<pEnd) 
        || (pCursor->desc && pCsr>pExpr->aDoclist) 
    ){
      if( pCursor->desc==0 && pExpr->iCurrent<iDocid ){
        fts3PoslistCopy(0, &pCsr);
        if( pCsr<pEnd ){
          fts3GetDeltaVarint(&pCsr, &pExpr->iCurrent);
        }
        pExpr->pCurrent = pCsr;
      }else if( pCursor->desc && pExpr->iCurrent>iDocid ){
        fts3GetReverseDeltaVarint(&pCsr, pExpr->aDoclist, &pExpr->iCurrent);
        fts3ReversePoslist(pExpr->aDoclist, &pCsr);
        pExpr->pCurrent = pCsr;
      }else{
        if( pExpr->iCurrent==iDocid ){
          int iThis = 0;
          if( iCol<0 ){
            /* If iCol is negative, return a pointer to the start of the
            ** position-list (instead of a pointer to the start of a list

Changes to test/fts3sort.test.

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  3   "SELECT docid, * FROM t1 WHERE t1 MATCH 'a*'"
  4   "SELECT docid, quote(matchinfo(t1)) FROM t1 WHERE t1 MATCH 'a*'"
  5   "SELECT docid, quote(matchinfo(t1,'pcnxals')) FROM t1 WHERE t1 MATCH 'b*'"
  6   "SELECT docid, * FROM t1 WHERE t1 MATCH 'a* b* c*'"
  7   "SELECT docid, * FROM t1 WHERE t1 MATCH 'aa OR da'"
  8   "SELECT docid, * FROM t1 WHERE t1 MATCH 'nosuchtoken'"
  9   "SELECT docid, snippet(t1) FROM t1 WHERE t1 MATCH 'aa OR da'"

} {

  unset -nocomplain A B C D
  set A_list [list]
  set B_list [list]
  set C_list [list]
  set D_list [list]







>







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  3   "SELECT docid, * FROM t1 WHERE t1 MATCH 'a*'"
  4   "SELECT docid, quote(matchinfo(t1)) FROM t1 WHERE t1 MATCH 'a*'"
  5   "SELECT docid, quote(matchinfo(t1,'pcnxals')) FROM t1 WHERE t1 MATCH 'b*'"
  6   "SELECT docid, * FROM t1 WHERE t1 MATCH 'a* b* c*'"
  7   "SELECT docid, * FROM t1 WHERE t1 MATCH 'aa OR da'"
  8   "SELECT docid, * FROM t1 WHERE t1 MATCH 'nosuchtoken'"
  9   "SELECT docid, snippet(t1) FROM t1 WHERE t1 MATCH 'aa OR da'"
  10  "SELECT docid, snippet(t1) FROM t1 WHERE t1 MATCH 'aa OR nosuchtoken'"
} {

  unset -nocomplain A B C D
  set A_list [list]
  set B_list [list]
  set C_list [list]
  set D_list [list]