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Overview
Comment:Improvements to likelihood processing so that commuting an unindexed term in the WHERE clause does not change the query plan.
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SHA1:6e6bded055cdbc902731687c86d92c39a3ba5904
User & Date: drh 2013-09-11 17:39:09
Context
2013-09-12
17:29
Merge in the Expr.flags expansion to 32-bits. Use an extra bit to help optimize the sqlite3ExprSkipCollate() routine. check-in: 4c84d1b4 user: drh tags: unlikely-func
2013-09-11
17:39
Improvements to likelihood processing so that commuting an unindexed term in the WHERE clause does not change the query plan. check-in: 6e6bded0 user: drh tags: unlikely-func
14:34
Additional unlikely() test cases. Logic tweaks to support test coverage. check-in: 5d00cce7 user: drh tags: unlikely-func
Changes
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Changes to src/where.c.

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    memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
    if( pOld!=pWC->aStatic ){
      sqlite3DbFree(db, pOld);
    }
    pWC->nSlot = sqlite3DbMallocSize(db, pWC->a)/sizeof(pWC->a[0]);
  }
  pTerm = &pWC->a[idx = pWC->nTerm++];
  if( wtFlags & TERM_VIRTUAL ){
    pTerm->truthProb = 0;
  }else if( ALWAYS(p) && ExprHasAnyProperty(p, EP_Hint) ){
    pTerm->truthProb = whereCost(p->iTable) - 99;
  }else{
    pTerm->truthProb = -1;
  }
  pTerm->pExpr = sqlite3ExprSkipCollate(p);
  pTerm->wtFlags = wtFlags;
  pTerm->pWC = pWC;
................................................................................
** index.
**
** In the current implementation, the first extra WHERE clause term reduces
** the number of output rows by a factor of 10 and each additional term
** reduces the number of output rows by sqrt(2).
*/
static void whereLoopOutputAdjust(WhereClause *pWC, WhereLoop *pLoop, int iCur){
  WhereTerm *pTerm;
  Bitmask notAllowed = ~(pLoop->prereq|pLoop->maskSelf);
  int x = 0;
  int i;

  if( !OptimizationEnabled(pWC->pWInfo->pParse->db, SQLITE_AdjustOutEst) ){
    return;
  }
  for(i=pWC->nTerm, pTerm=pWC->a; i>0; i--, pTerm++){
    if( (pTerm->wtFlags & TERM_VIRTUAL)!=0 ) continue;
    if( (pTerm->prereqAll & pLoop->maskSelf)==0 ) continue;
    if( (pTerm->prereqAll & notAllowed)!=0 ) continue;
    x += pTerm->truthProb;
  }
  for(i=pLoop->nLTerm-1; i>=0; i--){
    x -= pLoop->aLTerm[i]->truthProb;


  }
  if( x<0 ) pLoop->nOut += x;

}

/*
** We have so far matched pBuilder->pNew->u.btree.nEq terms of the index pIndex.
** Try to match one more.
**
** If pProbe->tnum==0, that means pIndex is a fake index used for the
................................................................................
                (pTo->rCost>=rCost && pTo->nRow>=nOut))
          ){
            testcase( jj==nTo-1 );
            break;
          }
        }
        if( jj>=nTo ){
          if( nTo>=mxChoice 
           && (rCost>mxCost || (rCost==mxCost && nOut>=mxOut))
          ){
#ifdef WHERETRACE_ENABLED
            if( sqlite3WhereTrace&0x4 ){
              sqlite3DebugPrintf("Skip   %s cost=%-3d,%3d order=%c\n",
                  wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
                  isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
            }
#endif







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    memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
    if( pOld!=pWC->aStatic ){
      sqlite3DbFree(db, pOld);
    }
    pWC->nSlot = sqlite3DbMallocSize(db, pWC->a)/sizeof(pWC->a[0]);
  }
  pTerm = &pWC->a[idx = pWC->nTerm++];


  if( p && ExprHasAnyProperty(p, EP_Hint) ){
    pTerm->truthProb = whereCost(p->iTable) - 99;
  }else{
    pTerm->truthProb = -1;
  }
  pTerm->pExpr = sqlite3ExprSkipCollate(p);
  pTerm->wtFlags = wtFlags;
  pTerm->pWC = pWC;
................................................................................
** index.
**
** In the current implementation, the first extra WHERE clause term reduces
** the number of output rows by a factor of 10 and each additional term
** reduces the number of output rows by sqrt(2).
*/
static void whereLoopOutputAdjust(WhereClause *pWC, WhereLoop *pLoop, int iCur){
  WhereTerm *pTerm, *pX;
  Bitmask notAllowed = ~(pLoop->prereq|pLoop->maskSelf);

  int i, j;

  if( !OptimizationEnabled(pWC->pWInfo->pParse->db, SQLITE_AdjustOutEst) ){
    return;
  }
  for(i=pWC->nTerm, pTerm=pWC->a; i>0; i--, pTerm++){
    if( (pTerm->wtFlags & TERM_VIRTUAL)!=0 ) break;
    if( (pTerm->prereqAll & pLoop->maskSelf)==0 ) continue;
    if( (pTerm->prereqAll & notAllowed)!=0 ) continue;


    for(j=pLoop->nLTerm-1; j>=0; j--){
      pX = pLoop->aLTerm[j];
      if( pX==pTerm ) break;
      if( pX->iParent>=0 && (&pWC->a[pX->iParent])==pTerm ) break;
    }
    if( j<0 ) pLoop->nOut += pTerm->truthProb;
  }
}

/*
** We have so far matched pBuilder->pNew->u.btree.nEq terms of the index pIndex.
** Try to match one more.
**
** If pProbe->tnum==0, that means pIndex is a fake index used for the
................................................................................
                (pTo->rCost>=rCost && pTo->nRow>=nOut))
          ){
            testcase( jj==nTo-1 );
            break;
          }
        }
        if( jj>=nTo ){
          if( nTo>=mxChoice && rCost>=mxCost ){


#ifdef WHERETRACE_ENABLED
            if( sqlite3WhereTrace&0x4 ){
              sqlite3DebugPrintf("Skip   %s cost=%-3d,%3d order=%c\n",
                  wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
                  isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
            }
#endif

Changes to test/whereG.test.

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    SELECT DISTINCT aname
      FROM album, composer, track
     WHERE likelihood(cname LIKE '%bach%', track.cid)
       AND composer.cid=track.cid
       AND album.aid=track.aid;
  }
} {1 {second argument to likelihood() must be a constant between 0.0 and 1.0}}





















finish_test








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    SELECT DISTINCT aname
      FROM album, composer, track
     WHERE likelihood(cname LIKE '%bach%', track.cid)
       AND composer.cid=track.cid
       AND album.aid=track.aid;
  }
} {1 {second argument to likelihood() must be a constant between 0.0 and 1.0}}

# Commuting a term of the WHERE clause should not change the query plan
#
do_execsql_test whereG-3.0 {
  CREATE TABLE a(a1 PRIMARY KEY, a2);
  CREATE TABLE b(b1 PRIMARY KEY, b2);
} {}
do_eqp_test whereG-3.1 {
  SELECT * FROM a, b WHERE b1=a1 AND a2=5;
} {/.*SCAN TABLE a.*SEARCH TABLE b USING INDEX .*b_1 .b1=..*/}
do_eqp_test whereG-3.2 {
  SELECT * FROM a, b WHERE a1=b1 AND a2=5;
} {/.*SCAN TABLE a.*SEARCH TABLE b USING INDEX .*b_1 .b1=..*/}
do_eqp_test whereG-3.3 {
  SELECT * FROM a, b WHERE a2=5 AND b1=a1;
} {/.*SCAN TABLE a.*SEARCH TABLE b USING INDEX .*b_1 .b1=..*/}
do_eqp_test whereG-3.4 {
  SELECT * FROM a, b WHERE a2=5 AND a1=b1;
} {/.*SCAN TABLE a.*SEARCH TABLE b USING INDEX .*b_1 .b1=..*/}


finish_test