SQLite

#define TRACE_IDX_OUTPUTS(A)
#endif

/* 
** Required because bestIndex() is called by bestOrClauseIndex() 
*/
static void bestIndex(
    Parse*, WhereClause*, struct SrcList_item*,
    Bitmask, Bitmask, ExprList*, WhereCost*);

/*
** This routine attempts to find an scanning strategy that can be used 
** to optimize an 'OR' expression that is part of a WHERE clause. 
**
** The table associated with FROM clause term pSrc may be either a
** regular B-Tree table or a virtual table.
*/
static void bestOrClauseIndex(
  Parse *pParse,              /* The parsing context */
  WhereClause *pWC,           /* The WHERE clause */
  struct SrcList_item *pSrc,  /* The FROM clause term to search */
  Bitmask notReady,           /* Mask of cursors not available for indexing */
  Bitmask notValid,           /* Cursors not available for any purpose */
  ExprList *pOrderBy,         /* The ORDER BY clause */
  WhereCost *pCost            /* Lowest cost query plan */
){
#ifndef SQLITE_OMIT_OR_OPTIMIZATION
  const int iCur = pSrc->iCursor;   /* The cursor of the table to be accessed */
  const Bitmask maskSrc = getMask(pWC->pMaskSet, iCur);  /* Bitmask for pSrc */
  WhereTerm * const pWCEnd = &pWC->a[pWC->nTerm];        /* End of pWC->a[] */

      for(pOrTerm=pOrWC->a; pOrTerm<pOrWCEnd; pOrTerm++){
        WhereCost sTermCost;
        WHERETRACE(("... Multi-index OR testing for term %d of %d....\n", 
          (pOrTerm - pOrWC->a), (pTerm - pWC->a)
        ));
        if( pOrTerm->eOperator==WO_AND ){
          WhereClause *pAndWC = &pOrTerm->u.pAndInfo->wc;
          bestIndex(pParse, pAndWC, pSrc, notReady, notValid, 0, &sTermCost);
        }else if( pOrTerm->leftCursor==iCur ){
          WhereClause tempWC;
          tempWC.pParse = pWC->pParse;
          tempWC.pMaskSet = pWC->pMaskSet;
          tempWC.op = TK_AND;
          tempWC.a = pOrTerm;
          tempWC.nTerm = 1;
          bestIndex(pParse, &tempWC, pSrc, notReady, notValid, 0, &sTermCost);
        }else{
          continue;
        }
        rTotal += sTermCost.rCost;
        nRow += sTermCost.nRow;
        used |= sTermCost.used;
        if( rTotal>=pCost->rCost ) break;

** routine takes care of freeing the sqlite3_index_info structure after
** everybody has finished with it.
*/
static void bestVirtualIndex(
  Parse *pParse,                  /* The parsing context */
  WhereClause *pWC,               /* The WHERE clause */
  struct SrcList_item *pSrc,      /* The FROM clause term to search */
  Bitmask notReady,               /* Mask of cursors not available for index */
  Bitmask notValid,               /* Cursors not valid for any purpose */
  ExprList *pOrderBy,             /* The order by clause */
  WhereCost *pCost,               /* Lowest cost query plan */
  sqlite3_index_info **ppIdxInfo  /* Index information passed to xBestIndex */
){
  Table *pTab = pSrc->pTab;
  sqlite3_index_info *pIdxInfo;
  struct sqlite3_index_constraint *pIdxCons;

  }
  pCost->plan.nEq = 0;
  pIdxInfo->nOrderBy = nOrderBy;

  /* Try to find a more efficient access pattern by using multiple indexes
  ** to optimize an OR expression within the WHERE clause. 
  */
  bestOrClauseIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost);
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */

/*
** Argument pIdx is a pointer to an index structure that has an array of
** SQLITE_INDEX_SAMPLES evenly spaced samples of the first indexed column
** stored in Index.aSample. The domain of values stored in said column

** selected plan may still take advantage of the tables built-in rowid
** index.
*/
static void bestBtreeIndex(
  Parse *pParse,              /* The parsing context */
  WhereClause *pWC,           /* The WHERE clause */
  struct SrcList_item *pSrc,  /* The FROM clause term to search */
  Bitmask notReady,           /* Mask of cursors not available for indexing */
  Bitmask notValid,           /* Cursors not available for any purpose */
  ExprList *pOrderBy,         /* The ORDER BY clause */
  WhereCost *pCost            /* Lowest cost query plan */
){
  int iCur = pSrc->iCursor;   /* The cursor of the table to be accessed */
  Index *pProbe;              /* An index we are evaluating */
  Index *pIdx;                /* Copy of pProbe, or zero for IPK index */
  int eqTermMask;             /* Current mask of valid equality operators */

    /* If there are additional constraints on this table that cannot
    ** be used with the current index, but which might lower the number
    ** of output rows, adjust the nRow value accordingly.  This only 
    ** matters if the current index is the least costly, so do not bother
    ** with this step if we already know this index will not be chosen.
    ** Also, never reduce the output row count below 2 using this step.
    **
    ** It is critical that the notValid mask be used here instead of


    ** the notReady mask.  When computing an "optimal" index, the notReady

    ** mask will only have one bit set - the bit for the current table.
    ** The notValid mask, on the other hand, always has all bits set for
    ** tables that are not in outer loops.  If notReady is used here instead
    ** of notValid, then a optimal index that depends on inner joins loops
    ** might be selected even when there exists an optimal index that has
    ** no such dependency.
    */
    if( nRow>2 && cost<=pCost->rCost ){
      int k;                       /* Loop counter */
      int nSkipEq = nEq;           /* Number of == constraints to skip */
      int nSkipRange = nBound;     /* Number of < constraints to skip */
      Bitmask thisTab;             /* Bitmap for pSrc */

      thisTab = getMask(pWC->pMaskSet, iCur);
      for(pTerm=pWC->a, k=pWC->nTerm; nRow>2 && k; k--, pTerm++){
        if( pTerm->wtFlags & TERM_VIRTUAL ) continue;
        if( (pTerm->prereqAll & notValid)!=thisTab ) continue;
        if( pTerm->eOperator & (WO_EQ|WO_IN|WO_ISNULL) ){
          if( nSkipEq ){
            /* Ignore the first nEq equality matches since the index
            ** has already accounted for these */
            nSkipEq--;
          }else{
            /* Assume each additional equality match reduces the result

  );

  WHERETRACE(("best index is: %s\n", 
    ((pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)==0 ? "none" : 
         pCost->plan.u.pIdx ? pCost->plan.u.pIdx->zName : "ipk")
  ));
  
  bestOrClauseIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost);
  bestAutomaticIndex(pParse, pWC, pSrc, notReady, pCost);
  pCost->plan.wsFlags |= eqTermMask;
}

/*
** Find the query plan for accessing table pSrc->pTab. Write the
** best query plan and its cost into the WhereCost object supplied 
** as the last parameter. This function may calculate the cost of
** both real and virtual table scans.
*/
static void bestIndex(
  Parse *pParse,              /* The parsing context */
  WhereClause *pWC,           /* The WHERE clause */
  struct SrcList_item *pSrc,  /* The FROM clause term to search */
  Bitmask notReady,           /* Mask of cursors not available for indexing */
  Bitmask notValid,           /* Cursors not available for any purpose */
  ExprList *pOrderBy,         /* The ORDER BY clause */
  WhereCost *pCost            /* Lowest cost query plan */
){
#ifndef SQLITE_OMIT_VIRTUALTABLE
  if( IsVirtual(pSrc->pTab) ){
    sqlite3_index_info *p = 0;
    bestVirtualIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost,&p);
    if( p->needToFreeIdxStr ){
      sqlite3_free(p->idxStr);
    }
    sqlite3DbFree(pParse->db, p);
  }else
#endif
  {
    bestBtreeIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost);
  }
}

/*
** Disable a term in the WHERE clause.  Except, do not disable the term
** if it controls a LEFT OUTER JOIN and it did not originate in the ON
** or USING clause of that join.

    ** were used as the innermost nested loop.  In other words, a table
    ** is chosen such that the cost of running that table cannot be reduced
    ** by waiting for other tables to run first.  This "optimal" test works
    ** by first assuming that the FROM clause is on the inner loop and finding
    ** its query plan, then checking to see if that query plan uses any
    ** other FROM clause terms that are notReady.  If no notReady terms are
    ** used then the "optimal" query plan works.
    **
    ** Note that the WhereCost.nRow parameter for an optimal scan might
    ** not be as small as it would be if the table really were the innermost
    ** join.  The nRow value can be reduced by WHERE clause constraints
    ** that do not use indices.  But this nRow reduction only happens if the
    ** table really is the innermost join.  
    **
    ** The second loop iteration is only performed if no optimal scan
    ** strategies were found by the first iteration. This second iteration
    ** is used to search for the lowest cost scan overall.
    **
    ** Previous versions of SQLite performed only the second iteration -
    ** the next outermost loop was always that with the lowest overall
    ** cost. However, this meant that SQLite could select the wrong plan
    ** for scripts such as the following:
    **   
    **   CREATE TABLE t1(a, b); 
    **   CREATE TABLE t2(c, d);
    **   SELECT * FROM t2, t1 WHERE t2.rowid = t1.a;
    **
    ** The best strategy is to iterate through table t1 first. However it
    ** is not possible to determine this with a simple greedy algorithm.
    ** Since the cost of a linear scan through table t2 is the same 
    ** as the cost of a linear scan through table t1, a simple greedy 
    ** algorithm may choose to use t2 for the outer loop, which is a much
    ** costlier approach.
    */
    nUnconstrained = 0;
    notIndexed = 0;
    for(isOptimal=(iFrom<nTabList-1); isOptimal>=0 && bestJ<0; isOptimal--){
      Bitmask mask;             /* Mask of tables not yet ready */
      for(j=iFrom, pTabItem=&pTabList->a[j]; j<nTabList; j++, pTabItem++){
        int doNotReorder;    /* True if this table should not be reordered */
        WhereCost sCost;     /* Cost information from best[Virtual]Index() */
        ExprList *pOrderBy;  /* ORDER BY clause for index to optimize */
  
        doNotReorder =  (pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0;

        pOrderBy = ((i==0 && ppOrderBy )?*ppOrderBy:0);
        if( pTabItem->pIndex==0 ) nUnconstrained++;
  
        assert( pTabItem->pTab );
#ifndef SQLITE_OMIT_VIRTUALTABLE
        if( IsVirtual(pTabItem->pTab) ){
          sqlite3_index_info **pp = &pWInfo->a[j].pIdxInfo;
          bestVirtualIndex(pParse, pWC, pTabItem, mask, notReady, pOrderBy,
                           &sCost, pp);
        }else 
#endif
        {
          bestBtreeIndex(pParse, pWC, pTabItem, mask, notReady, pOrderBy,
                         &sCost);
        }
        assert( isOptimal || (sCost.used&notReady)==0 );

        /* If an INDEXED BY clause is present, then the plan must use that
        ** index if it uses any index at all */
        assert( pTabItem->pIndex==0 
                  || (sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)==0

} {0 1 {TABLE t401} 1 0 {TABLE t400} 2 2 {TABLE t402}}
do_test where3-4.2 {
  execsql {
    EXPLAIN QUERY PLAN
    SELECT * FROM t400, t401, t402 WHERE t400.c GLOB 'abc*';
  }
} {0 0 {TABLE t400} 1 1 {TABLE t401} 2 2 {TABLE t402}}

# Verify that a performance regression encountered by firefox
# has been fixed.
#
do_test where3-5.0 {
  execsql {
     CREATE TABLE aaa (id INTEGER PRIMARY KEY, type INTEGER,
                       fk INTEGER DEFAULT NULL, parent INTEGER,
                       position INTEGER, title LONGVARCHAR,
                       keyword_id INTEGER, folder_type TEXT,
                       dateAdded INTEGER, lastModified INTEGER);
     CREATE INDEX aaa_111 ON aaa (fk, type);
     CREATE INDEX aaa_222 ON aaa (parent, position);
     CREATE INDEX aaa_333 ON aaa (fk, lastModified);
     CREATE TABLE bbb (id INTEGER PRIMARY KEY, type INTEGER,
                       fk INTEGER DEFAULT NULL, parent INTEGER,
                       position INTEGER, title LONGVARCHAR,
                       keyword_id INTEGER, folder_type TEXT,
                       dateAdded INTEGER, lastModified INTEGER);
     CREATE INDEX bbb_111 ON bbb (fk, type);
     CREATE INDEX bbb_222 ON bbb (parent, position);
     CREATE INDEX bbb_333 ON bbb (fk, lastModified);
  }

  execsql {
    EXPLAIN QUERY PLAN
     SELECT bbb.title AS tag_title 
       FROM aaa JOIN bbb ON bbb.id = aaa.parent  
      WHERE aaa.fk = 'constant'
        AND LENGTH(bbb.title) > 0
        AND bbb.parent = 4
      ORDER BY bbb.title COLLATE NOCASE ASC;
  }
} {0 0 {TABLE aaa WITH INDEX aaa_333} 1 1 {TABLE bbb USING PRIMARY KEY}}
do_test where3-5.1 {
  execsql {
    EXPLAIN QUERY PLAN
     SELECT bbb.title AS tag_title 
       FROM aaa JOIN aaa AS bbb ON bbb.id = aaa.parent  
      WHERE aaa.fk = 'constant'
        AND LENGTH(bbb.title) > 0
        AND bbb.parent = 4
      ORDER BY bbb.title COLLATE NOCASE ASC;
  }
} {0 0 {TABLE aaa WITH INDEX aaa_333} 1 1 {TABLE aaa AS bbb USING PRIMARY KEY}}
do_test where3-5.2 {
  execsql {
    EXPLAIN QUERY PLAN
     SELECT bbb.title AS tag_title 
       FROM bbb JOIN aaa ON bbb.id = aaa.parent  
      WHERE aaa.fk = 'constant'
        AND LENGTH(bbb.title) > 0
        AND bbb.parent = 4
      ORDER BY bbb.title COLLATE NOCASE ASC;
  }
} {0 1 {TABLE aaa WITH INDEX aaa_333} 1 0 {TABLE bbb USING PRIMARY KEY}}
do_test where3-5.3 {
  execsql {
    EXPLAIN QUERY PLAN
     SELECT bbb.title AS tag_title 
       FROM aaa AS bbb JOIN aaa ON bbb.id = aaa.parent  
      WHERE aaa.fk = 'constant'
        AND LENGTH(bbb.title) > 0
        AND bbb.parent = 4
      ORDER BY bbb.title COLLATE NOCASE ASC;
  }
} {0 1 {TABLE aaa WITH INDEX aaa_333} 1 0 {TABLE aaa AS bbb USING PRIMARY KEY}}


finish_test