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Overview
Comment:Add WHERETRACE debugging output to the whereLoopAdjustCost() routine.
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SHA1:ec1e942f08548695ff02645b3f3cd6bb2516bc9a
User & Date: drh 2014-10-21 16:01:40
Original Comment: Improvements to the WHERETRACE debugging logic.
Context
2014-10-21
18:16
Further tuning of the cost estimates for skip-scan loops, especially for cases when skip-scan loops are in competition with regular loops. check-in: a27861c2 user: drh tags: trunk
16:01
Add WHERETRACE debugging output to the whereLoopAdjustCost() routine. check-in: ec1e942f user: drh tags: trunk
01:05
If a skip-scan is a proper subset of some other scan, then adjust the cost of the skip-scan upward so that it is more costly than the other scan. Such a cost imbalance can arise under STAT4 because of difficulties in getting an accurate estimate for skip-scans. check-in: f4b22a26 user: drh tags: trunk
Changes
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Changes to src/where.c.

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  if( (pTemplate->wsFlags & WHERE_INDEXED)==0 ) return;
  for(; p; p=p->pNextLoop){
    if( p->iTab!=pTemplate->iTab ) continue;
    if( (p->wsFlags & WHERE_INDEXED)==0 ) continue;
    if( whereLoopCheaperProperSubset(p, pTemplate) ){
      /* Adjust pTemplate cost downward so that it is cheaper than its 
      ** subset p */


      pTemplate->rRun = p->rRun;
      pTemplate->nOut = p->nOut - 1;
    }else if( whereLoopCheaperProperSubset(pTemplate, p) ){
      /* Adjust pTemplate cost upward so that it is costlier than p since
      ** pTemplate is a proper subset of p */


      pTemplate->rRun = p->rRun;
      pTemplate->nOut = p->nOut + 1;
    }
  }
}

/*
................................................................................
            }
          }
        }
      }
    }

#ifdef WHERETRACE_ENABLED  /* >=2 */
    if( sqlite3WhereTrace>=2 ){
      sqlite3DebugPrintf("---- after round %d ----\n", iLoop);
      for(ii=0, pTo=aTo; ii<nTo; ii++, pTo++){
        sqlite3DebugPrintf(" %s cost=%-3d nrow=%-3d order=%c",
           wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
           pTo->isOrdered>=0 ? (pTo->isOrdered+'0') : '?');
        if( pTo->isOrdered>0 ){
          sqlite3DebugPrintf(" rev=0x%llx\n", pTo->revLoop);







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  if( (pTemplate->wsFlags & WHERE_INDEXED)==0 ) return;
  for(; p; p=p->pNextLoop){
    if( p->iTab!=pTemplate->iTab ) continue;
    if( (p->wsFlags & WHERE_INDEXED)==0 ) continue;
    if( whereLoopCheaperProperSubset(p, pTemplate) ){
      /* Adjust pTemplate cost downward so that it is cheaper than its 
      ** subset p */
      WHERETRACE(0x80,("subset cost adjustment %d,%d to %d,%d\n",
                       pTemplate->rRun, pTemplate->nOut, p->rRun, p->nOut-1));
      pTemplate->rRun = p->rRun;
      pTemplate->nOut = p->nOut - 1;
    }else if( whereLoopCheaperProperSubset(pTemplate, p) ){
      /* Adjust pTemplate cost upward so that it is costlier than p since
      ** pTemplate is a proper subset of p */
      WHERETRACE(0x80,("subset cost adjustment %d,%d to %d,%d\n",
                       pTemplate->rRun, pTemplate->nOut, p->rRun, p->nOut+1));
      pTemplate->rRun = p->rRun;
      pTemplate->nOut = p->nOut + 1;
    }
  }
}

/*
................................................................................
            }
          }
        }
      }
    }

#ifdef WHERETRACE_ENABLED  /* >=2 */
    if( sqlite3WhereTrace & 0x02 ){
      sqlite3DebugPrintf("---- after round %d ----\n", iLoop);
      for(ii=0, pTo=aTo; ii<nTo; ii++, pTo++){
        sqlite3DebugPrintf(" %s cost=%-3d nrow=%-3d order=%c",
           wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
           pTo->isOrdered>=0 ? (pTo->isOrdered+'0') : '?');
        if( pTo->isOrdered>0 ){
          sqlite3DebugPrintf(" rev=0x%llx\n", pTo->revLoop);