diff options
Diffstat (limited to 'src/select.c')
| -rw-r--r-- | src/select.c | 62 |
1 files changed, 35 insertions, 27 deletions
diff --git a/src/select.c b/src/select.c index d7ba1f806..3def13618 100644 --- a/src/select.c +++ b/src/select.c @@ -3154,6 +3154,8 @@ static int multiSelectOrderBy( typedef struct SubstContext { Parse *pParse; /* The parsing context */ int iTable; /* Replace references to this table */ + int iNewTable; /* New table number */ + int isLeftJoin; /* Add TK_IF_NULL_ROW opcodes on each replacement */ ExprList *pEList; /* Replacement expressions */ } SubstContext; @@ -3179,18 +3181,29 @@ static Expr *substExpr( Expr *pExpr /* Expr in which substitution occurs */ ){ if( pExpr==0 ) return 0; + if( ExprHasProperty(pExpr, EP_FromJoin) && pExpr->iRightJoinTable==pSubst->iTable ){ + pExpr->iRightJoinTable = pSubst->iNewTable; + } if( pExpr->op==TK_COLUMN && pExpr->iTable==pSubst->iTable ){ if( pExpr->iColumn<0 ){ pExpr->op = TK_NULL; }else{ Expr *pNew; Expr *pCopy = pSubst->pEList->a[pExpr->iColumn].pExpr; + Expr ifNullRow; assert( pSubst->pEList!=0 && pExpr->iColumn<pSubst->pEList->nExpr ); assert( pExpr->pLeft==0 && pExpr->pRight==0 ); if( sqlite3ExprIsVector(pCopy) ){ sqlite3VectorErrorMsg(pSubst->pParse, pCopy); }else{ sqlite3 *db = pSubst->pParse->db; + if( pSubst->isLeftJoin && pCopy->op!=TK_COLUMN ){ + memset(&ifNullRow, 0, sizeof(ifNullRow)); + ifNullRow.op = TK_IF_NULL_ROW; + ifNullRow.pLeft = pCopy; + ifNullRow.iTable = pSubst->iNewTable; + pCopy = &ifNullRow; + } pNew = sqlite3ExprDup(db, pCopy, 0); if( pNew && (pExpr->flags & EP_FromJoin) ){ pNew->iRightJoinTable = pExpr->iRightJoinTable; @@ -3284,8 +3297,8 @@ static void substSelect( ** FROM-clause subquery that is a candidate for flattening. (2b is ** due to ticket [2f7170d73bf9abf80] from 2015-02-09.) ** -** (3) The subquery is not the right operand of a left outer join -** (Originally ticket #306. Strengthened by ticket #3300) +** (3) The subquery is not the right operand of a LEFT JOIN +** or the subquery is not itself a join. ** ** (4) The subquery is not DISTINCT. ** @@ -3297,7 +3310,7 @@ static void substSelect( ** DISTINCT. ** ** (7) The subquery has a FROM clause. TODO: For subqueries without -** A FROM clause, consider adding a FROM close with the special +** A FROM clause, consider adding a FROM clause with the special ** table sqlite_once that consists of a single row containing a ** single NULL. ** @@ -3403,6 +3416,8 @@ static int flattenSubquery( SrcList *pSubSrc; /* The FROM clause of the subquery */ ExprList *pList; /* The result set of the outer query */ int iParent; /* VDBE cursor number of the pSub result set temp table */ + int iNewParent = -1;/* Replacement table for iParent */ + int isLeftJoin = 0; /* True if pSub is the right side of a LEFT JOIN */ int i; /* Loop counter */ Expr *pWhere; /* The WHERE clause */ struct SrcList_item *pSubitem; /* The subquery */ @@ -3429,7 +3444,7 @@ static int flattenSubquery( return 0; /* Restriction (2b) */ } } - + pSubSrc = pSub->pSrc; assert( pSubSrc ); /* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants, @@ -3467,10 +3482,9 @@ static int flattenSubquery( return 0; /* Restriction (23) */ } - /* OBSOLETE COMMENT 1: - ** Restriction 3: If the subquery is a join, make sure the subquery is - ** not used as the right operand of an outer join. Examples of why this - ** is not allowed: + /* + ** If the subquery is the right operand of a LEFT JOIN, then the + ** subquery may not be a join itself. Example of why this is not allowed: ** ** t1 LEFT OUTER JOIN (t2 JOIN t3) ** @@ -3480,27 +3494,13 @@ static int flattenSubquery( ** ** which is not at all the same thing. ** - ** OBSOLETE COMMENT 2: - ** Restriction 12: If the subquery is the right operand of a left outer - ** join, make sure the subquery has no WHERE clause. - ** An examples of why this is not allowed: - ** - ** t1 LEFT OUTER JOIN (SELECT * FROM t2 WHERE t2.x>0) - ** - ** If we flatten the above, we would get - ** - ** (t1 LEFT OUTER JOIN t2) WHERE t2.x>0 - ** - ** But the t2.x>0 test will always fail on a NULL row of t2, which - ** effectively converts the OUTER JOIN into an INNER JOIN. - ** - ** THIS OVERRIDES OBSOLETE COMMENTS 1 AND 2 ABOVE: - ** Ticket #3300 shows that flattening the right term of a LEFT JOIN - ** is fraught with danger. Best to avoid the whole thing. If the - ** subquery is the right term of a LEFT JOIN, then do not flatten. + ** See also tickets #306, #350, and #3300. */ if( (pSubitem->fg.jointype & JT_OUTER)!=0 ){ - return 0; + isLeftJoin = 1; + if( pSubSrc->nSrc>1 ){ + return 0; /* Restriction (3) */ + } } /* Restriction 17: If the sub-query is a compound SELECT, then it must @@ -3709,6 +3709,7 @@ static int flattenSubquery( sqlite3IdListDelete(db, pSrc->a[i+iFrom].pUsing); assert( pSrc->a[i+iFrom].fg.isTabFunc==0 ); pSrc->a[i+iFrom] = pSubSrc->a[i]; + iNewParent = pSubSrc->a[i].iCursor; memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i])); } pSrc->a[iFrom].fg.jointype = jointype; @@ -3754,6 +3755,9 @@ static int flattenSubquery( pSub->pOrderBy = 0; } pWhere = sqlite3ExprDup(db, pSub->pWhere, 0); + if( isLeftJoin ){ + setJoinExpr(pWhere, iNewParent); + } if( subqueryIsAgg ){ assert( pParent->pHaving==0 ); pParent->pHaving = pParent->pWhere; @@ -3770,6 +3774,8 @@ static int flattenSubquery( SubstContext x; x.pParse = pParse; x.iTable = iParent; + x.iNewTable = iNewParent; + x.isLeftJoin = isLeftJoin; x.pEList = pSub->pEList; substSelect(&x, pParent, 0); } @@ -3878,6 +3884,8 @@ static int pushDownWhereTerms( pNew = sqlite3ExprDup(pParse->db, pWhere, 0); x.pParse = pParse; x.iTable = iCursor; + x.iNewTable = iCursor; + x.isLeftJoin = 0; x.pEList = pSubq->pEList; pNew = substExpr(&x, pNew); pSubq->pWhere = sqlite3ExprAnd(pParse->db, pSubq->pWhere, pNew); |