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If a table is on the rhs of a LEFT JOIN, include only terms from the joins ON(...) clause in the cursor-hint passed via OP_CursorHint.

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FossilOrigin-Name: 2a2346b04235c6d0b7a8e64c92ee31018285c29f
This commit is contained in:
dan
2016-06-17 14:33:32 +00:00
parent 3480bfdae9
commit b324cf756e
4 changed files with 142 additions and 12 deletions
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35
src/wherecode.c
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@ -678,6 +678,7 @@ static int codeCursorHintFixExpr(Walker *pWalker, Expr *pExpr){
** Insert an OP_CursorHint instruction if it is appropriate to do so.
*/
static void codeCursorHint(
struct SrcList_item *pTabItem, /* FROM clause item */
WhereInfo *pWInfo, /* The where clause */
WhereLevel *pLevel, /* Which loop to provide hints for */
WhereTerm *pEndRange /* Hint this end-of-scan boundary term if not NULL */
@ -708,7 +709,31 @@ static void codeCursorHint(
pTerm = &pWC->a[i];
if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
if( pTerm->prereqAll & pLevel->notReady ) continue;
if( ExprHasProperty(pTerm->pExpr, EP_FromJoin) ) continue;
/* Any terms specified as part of the ON(...) clause for any LEFT
** JOIN for which the current table is not the rhs are omitted
** from the cursor-hint.
**
** If this table is the rhs of a LEFT JOIN, only terms that were
** specified as part of the ON(...) clause may be included in the
** hint. This is to address the following:
**
** SELECT ... t1 LEFT JOIN t2 ON (t1.a=t2.b) WHERE t2.c IS NULL;
**
** If the (t2.c IS NULL) constraint is pushed down to the cursor, it
** might filter out all rows that match (t1.a=t2.b), causing SQLite
** to add a row of NULL values to the output that should not be
** present (since the ON clause does actually match rows within t2).
*/
if( pTabItem->fg.jointype & JT_LEFT ){
if( !ExprHasProperty(pTerm->pExpr, EP_FromJoin)
|| pTerm->pExpr->iRightJoinTable!=pTabItem->iCursor
){
continue;
}
}else{
if( ExprHasProperty(pTerm->pExpr, EP_FromJoin) ) continue;
}
/* All terms in pWLoop->aLTerm[] except pEndRange are used to initialize
** the cursor. These terms are not needed as hints for a pure range
@ -742,7 +767,7 @@ static void codeCursorHint(
}
}
#else
# define codeCursorHint(A,B,C) /* No-op */
# define codeCursorHint(A,B,C,D) /* No-op */
#endif /* SQLITE_ENABLE_CURSOR_HINTS */
/*
@ -998,7 +1023,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
pStart = pEnd;
pEnd = pTerm;
}
codeCursorHint(pWInfo, pLevel, pEnd);
codeCursorHint(pTabItem, pWInfo, pLevel, pEnd);
if( pStart ){
Expr *pX; /* The expression that defines the start bound */
int r1, rTemp; /* Registers for holding the start boundary */
@ -1212,7 +1237,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
** and store the values of those terms in an array of registers
** starting at regBase.
*/
codeCursorHint(pWInfo, pLevel, pRangeEnd);
codeCursorHint(pTabItem, pWInfo, pLevel, pRangeEnd);
regBase = codeAllEqualityTerms(pParse,pLevel,bRev,nExtraReg,&zStartAff);
assert( zStartAff==0 || sqlite3Strlen30(zStartAff)>=nEq );
if( zStartAff ) cEndAff = zStartAff[nEq];
@ -1660,7 +1685,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
** a pseudo-cursor. No need to Rewind or Next such cursors. */
pLevel->op = OP_Noop;
}else{
codeCursorHint(pWInfo, pLevel, 0);
codeCursorHint(pTabItem, pWInfo, pLevel, 0);
pLevel->op = aStep[bRev];
pLevel->p1 = iCur;
pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);