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Add the TK_IF_NULL_ROW opcode to deal with non-NULL result columns in the

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result set of a view or subquery on the RHS of a LEFT JOIN that gets flattened.

FossilOrigin-Name: 3a5860d86fadcf924316707918bf283d26c53b1473e5e67f5cff59d18c2a7742
This commit is contained in:
drh
2017-04-14 19:03:10 +00:00
parent 399c7e21e4
commit 31d6fd5507
9 changed files with 83 additions and 47 deletions
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31
src/select.c
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@@ -3154,7 +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, or -1 */
int iNewTable; /* New table number */
int isLeftJoin; /* Add TK_IF_NULL_ROW opcodes on each replacement */
ExprList *pEList; /* Replacement expressions */
} SubstContext;
@@ -3189,12 +3190,20 @@ static Expr *substExpr(
}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;
@@ -3288,14 +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
** or (3b) the subquery is not a join and (3c) does not contain any
** result-set columns that could be non-NULL even if columns of the
** subquery table are NULL.
** to be more restrictive - disallowing subquery if it was the
** right operand of a left join. See tickets #306 and #3300. Relaxed
** to allow simple subqueries as the right operand of a left join
** on 2017-04-14.)
** (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.
**
@@ -3307,7 +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.
**
@@ -3491,15 +3494,13 @@ static int flattenSubquery(
**
** which is not at all the same thing.
**
** See also tickets #306 and #3300.
** See also tickets #306, #350, and #3300.
*/
if( (pSubitem->fg.jointype & JT_OUTER)!=0 ){
isLeftJoin = 1;
if( pSubSrc->nSrc>1 ){
return 0; /* Restriction (3b) */
return 0; /* Restriction (3) */
}
/* TBD: Deal with the case of result-set expressions that are non-NULL even
** when the RHS table of a LEFT JOIN is NULL. */
}
/* Restriction 17: If the sub-query is a compound SELECT, then it must
@@ -3774,6 +3775,7 @@ static int flattenSubquery(
x.pParse = pParse;
x.iTable = iParent;
x.iNewTable = iNewParent;
x.isLeftJoin = isLeftJoin;
x.pEList = pSub->pEList;
substSelect(&x, pParent, 0);
}
@@ -3883,6 +3885,7 @@ static int pushDownWhereTerms(
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);