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Overview
Comment:Make sure that the transitive constraint optimization does not cause WHERE clause terms to be disabled prematurely. We are unable to find a test case that fails because of this, but it seems prudent to make this preventative change nevertheless.
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SHA1: d6e361d7fb8013d616af91ef2c10038c97d1be5f
User & Date: drh 2013-09-09 19:37:46
Context
2013-09-10
01:41
Deterministically initialize the PRNG used as a tie-breaker in the ANALYZE command, so that the analysis is always the same given the same database. This simplifies testing. check-in: 48ed8b56 user: drh tags: trunk
2013-09-09
19:37
Make sure that the transitive constraint optimization does not cause WHERE clause terms to be disabled prematurely. We are unable to find a test case that fails because of this, but it seems prudent to make this preventative change nevertheless. check-in: d6e361d7 user: drh tags: trunk
2013-09-06
13:10
Combine the FuncDef.iPrefEnc and FuncDef.flags fields into a single new FuncDef.funcFlags field. check-in: 97b10e66 user: drh tags: trunk
Changes
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Changes to src/where.c.

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        int addrInTop;         /* Top of the IN loop */
        u8 eEndLoopOp;         /* IN Loop terminator. OP_Next or OP_Prev */
      } *aInLoop;           /* Information about each nested IN operator */
    } in;                 /* Used when pWLoop->wsFlags&WHERE_IN_ABLE */
    Index *pCovidx;       /* Possible covering index for WHERE_MULTI_OR */
  } u;
  struct WhereLoop *pWLoop;  /* The selected WhereLoop object */

};

/*
** Each instance of this object represents an algorithm for evaluating one
** term of a join.  Every term of the FROM clause will have at least
** one corresponding WhereLoop object (unless INDEXED BY constraints
** prevent a query solution - which is an error) and many terms of the
................................................................................
** as we can without disabling too much.  If we disabled in (1), we'd get
** the wrong answer.  See ticket #813.
*/
static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
  if( pTerm
      && (pTerm->wtFlags & TERM_CODED)==0
      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))

  ){
    pTerm->wtFlags |= TERM_CODED;
    if( pTerm->iParent>=0 ){
      WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
      if( (--pOther->nChild)==0 ){
        disableTerm(pLevel, pOther);
      }
................................................................................
  sqlite3 *db;                    /* Database connection */
  Vdbe *v;                        /* The prepared stmt under constructions */
  struct SrcList_item *pTabItem;  /* FROM clause term being coded */
  int addrBrk;                    /* Jump here to break out of the loop */
  int addrCont;                   /* Jump here to continue with next cycle */
  int iRowidReg = 0;        /* Rowid is stored in this register, if not zero */
  int iReleaseReg = 0;      /* Temp register to free before returning */
  Bitmask newNotReady;      /* Return value */

  pParse = pWInfo->pParse;
  v = pParse->pVdbe;
  pWC = &pWInfo->sWC;
  db = pParse->db;
  pLevel = &pWInfo->a[iLevel];
  pLoop = pLevel->pWLoop;
  pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
  iCur = pTabItem->iCursor;

  bRev = (pWInfo->revMask>>iLevel)&1;
  omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0 
           && (pWInfo->wctrlFlags & WHERE_FORCE_TABLE)==0;
  VdbeNoopComment((v, "Begin Join Loop %d", iLevel));

  /* Create labels for the "break" and "continue" instructions
  ** for the current loop.  Jump to addrBrk to break out of a loop.
................................................................................
    static const u8 aStart[] = { OP_Rewind, OP_Last };
    assert( bRev==0 || bRev==1 );
    pLevel->op = aStep[bRev];
    pLevel->p1 = iCur;
    pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
    pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
  }
  newNotReady = notReady & ~getMask(&pWInfo->sMaskSet, iCur);

  /* Insert code to test every subexpression that can be completely
  ** computed using the current set of tables.
  */
  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
    Expr *pE;
    testcase( pTerm->wtFlags & TERM_VIRTUAL );
    testcase( pTerm->wtFlags & TERM_CODED );
    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
    if( (pTerm->prereqAll & newNotReady)!=0 ){
      testcase( pWInfo->untestedTerms==0
               && (pWInfo->wctrlFlags & WHERE_ONETABLE_ONLY)!=0 );
      pWInfo->untestedTerms = 1;
      continue;
    }
    pE = pTerm->pExpr;
    assert( pE!=0 );
................................................................................
    WhereTerm *pAlt;
    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
    if( pTerm->eOperator!=(WO_EQUIV|WO_EQ) ) continue;
    if( pTerm->leftCursor!=iCur ) continue;
    if( pLevel->iLeftJoin ) continue;
    pE = pTerm->pExpr;
    assert( !ExprHasProperty(pE, EP_FromJoin) );
    assert( (pTerm->prereqRight & newNotReady)!=0 );
    pAlt = findTerm(pWC, iCur, pTerm->u.leftColumn, notReady, WO_EQ|WO_IN, 0);
    if( pAlt==0 ) continue;
    if( pAlt->wtFlags & (TERM_CODED) ) continue;
    testcase( pAlt->eOperator & WO_EQ );
    testcase( pAlt->eOperator & WO_IN );
    VdbeNoopComment((v, "begin transitive constraint"));
    pEAlt = sqlite3StackAllocRaw(db, sizeof(*pEAlt));
................................................................................
    sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
    VdbeComment((v, "record LEFT JOIN hit"));
    sqlite3ExprCacheClear(pParse);
    for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
      testcase( pTerm->wtFlags & TERM_VIRTUAL );
      testcase( pTerm->wtFlags & TERM_CODED );
      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
      if( (pTerm->prereqAll & newNotReady)!=0 ){
        assert( pWInfo->untestedTerms );
        continue;
      }
      assert( pTerm->pExpr );
      sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
      pTerm->wtFlags |= TERM_CODED;
    }
  }
  sqlite3ReleaseTempReg(pParse, iReleaseReg);

  return newNotReady;
}

#ifdef WHERETRACE_ENABLED
/*
** Print a WhereLoop object for debugging purposes
*/
static void whereLoopPrint(WhereLoop *p, SrcList *pTabList){







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        int addrInTop;         /* Top of the IN loop */
        u8 eEndLoopOp;         /* IN Loop terminator. OP_Next or OP_Prev */
      } *aInLoop;           /* Information about each nested IN operator */
    } in;                 /* Used when pWLoop->wsFlags&WHERE_IN_ABLE */
    Index *pCovidx;       /* Possible covering index for WHERE_MULTI_OR */
  } u;
  struct WhereLoop *pWLoop;  /* The selected WhereLoop object */
  Bitmask notReady;          /* FROM entries not usable at this level */
};

/*
** Each instance of this object represents an algorithm for evaluating one
** term of a join.  Every term of the FROM clause will have at least
** one corresponding WhereLoop object (unless INDEXED BY constraints
** prevent a query solution - which is an error) and many terms of the
................................................................................
** as we can without disabling too much.  If we disabled in (1), we'd get
** the wrong answer.  See ticket #813.
*/
static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
  if( pTerm
      && (pTerm->wtFlags & TERM_CODED)==0
      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
      && (pLevel->notReady & pTerm->prereqAll)==0
  ){
    pTerm->wtFlags |= TERM_CODED;
    if( pTerm->iParent>=0 ){
      WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
      if( (--pOther->nChild)==0 ){
        disableTerm(pLevel, pOther);
      }
................................................................................
  sqlite3 *db;                    /* Database connection */
  Vdbe *v;                        /* The prepared stmt under constructions */
  struct SrcList_item *pTabItem;  /* FROM clause term being coded */
  int addrBrk;                    /* Jump here to break out of the loop */
  int addrCont;                   /* Jump here to continue with next cycle */
  int iRowidReg = 0;        /* Rowid is stored in this register, if not zero */
  int iReleaseReg = 0;      /* Temp register to free before returning */


  pParse = pWInfo->pParse;
  v = pParse->pVdbe;
  pWC = &pWInfo->sWC;
  db = pParse->db;
  pLevel = &pWInfo->a[iLevel];
  pLoop = pLevel->pWLoop;
  pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
  iCur = pTabItem->iCursor;
  pLevel->notReady = notReady & ~getMask(&pWInfo->sMaskSet, iCur);
  bRev = (pWInfo->revMask>>iLevel)&1;
  omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0 
           && (pWInfo->wctrlFlags & WHERE_FORCE_TABLE)==0;
  VdbeNoopComment((v, "Begin Join Loop %d", iLevel));

  /* Create labels for the "break" and "continue" instructions
  ** for the current loop.  Jump to addrBrk to break out of a loop.
................................................................................
    static const u8 aStart[] = { OP_Rewind, OP_Last };
    assert( bRev==0 || bRev==1 );
    pLevel->op = aStep[bRev];
    pLevel->p1 = iCur;
    pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
    pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
  }


  /* Insert code to test every subexpression that can be completely
  ** computed using the current set of tables.
  */
  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
    Expr *pE;
    testcase( pTerm->wtFlags & TERM_VIRTUAL );
    testcase( pTerm->wtFlags & TERM_CODED );
    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
    if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
      testcase( pWInfo->untestedTerms==0
               && (pWInfo->wctrlFlags & WHERE_ONETABLE_ONLY)!=0 );
      pWInfo->untestedTerms = 1;
      continue;
    }
    pE = pTerm->pExpr;
    assert( pE!=0 );
................................................................................
    WhereTerm *pAlt;
    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
    if( pTerm->eOperator!=(WO_EQUIV|WO_EQ) ) continue;
    if( pTerm->leftCursor!=iCur ) continue;
    if( pLevel->iLeftJoin ) continue;
    pE = pTerm->pExpr;
    assert( !ExprHasProperty(pE, EP_FromJoin) );
    assert( (pTerm->prereqRight & pLevel->notReady)!=0 );
    pAlt = findTerm(pWC, iCur, pTerm->u.leftColumn, notReady, WO_EQ|WO_IN, 0);
    if( pAlt==0 ) continue;
    if( pAlt->wtFlags & (TERM_CODED) ) continue;
    testcase( pAlt->eOperator & WO_EQ );
    testcase( pAlt->eOperator & WO_IN );
    VdbeNoopComment((v, "begin transitive constraint"));
    pEAlt = sqlite3StackAllocRaw(db, sizeof(*pEAlt));
................................................................................
    sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
    VdbeComment((v, "record LEFT JOIN hit"));
    sqlite3ExprCacheClear(pParse);
    for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
      testcase( pTerm->wtFlags & TERM_VIRTUAL );
      testcase( pTerm->wtFlags & TERM_CODED );
      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
      if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
        assert( pWInfo->untestedTerms );
        continue;
      }
      assert( pTerm->pExpr );
      sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
      pTerm->wtFlags |= TERM_CODED;
    }
  }
  sqlite3ReleaseTempReg(pParse, iReleaseReg);

  return pLevel->notReady;
}

#ifdef WHERETRACE_ENABLED
/*
** Print a WhereLoop object for debugging purposes
*/
static void whereLoopPrint(WhereLoop *p, SrcList *pTabList){