/ Check-in [f538d759]
Login
SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:The query planner fix of check-in [33b1f584ef] should have been on the trunk.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: f538d759beda67e042b66181b65bd432488f7650
User & Date: drh 2010-04-15 13:29:38
Context
2010-04-15
23:24
Disable query flattening when the outer query is a compound SELECT and the inner query has a LIMIT clause. Ticket [02a8e81d44]. check-in: f96782b3 user: drh tags: trunk
13:29
The query planner fix of check-in [33b1f584ef] should have been on the trunk. check-in: f538d759 user: drh tags: trunk
01:04
Further refinements to table order selection on join query planning. check-in: defaf0d9 user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/where.c.

2733
2734
2735
2736
2737
2738
2739









2740
2741
2742

2743
2744


2745
2746
2747
2748
2749
2750
2751
2752

    /* 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.









    */
    if( nRow>2 && cost<=pCost->rCost ){
      int k;

      int nSkipEq = nEq;
      int nSkipRange = nBound;


      Bitmask 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 & notReady)!=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 */







>
>
>
>
>
>
>
>
>

|
<
>
|
|
>
>
|







2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750

2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763

    /* 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.
    **
    ** Do not reduce the output row count if pSrc is the only table that
    ** is notReady; if notReady is a power of two.  This will be the case
    ** when the main sqlite3WhereBegin() loop is scanning for a table with
    ** and "optimal" index, and on such a scan the output row count
    ** reduction is not valid because it does not update the "pCost->used"
    ** bitmap.  The notReady bitmap will also be a power of two when we
    ** are scanning for the last table in a 64-way join.  We are willing
    ** to bypass this optimization in that corner case.
    */
    if( nRow>2 && cost<=pCost->rCost && (notReady & (notReady-1))!=0 ){

      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 & notReady)!=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 */