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Provide tunable knob for x = NULL -> x IS NULL transformation, default to off.

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This commit is contained in:
Peter Eisentraut
2001-09-20 14:20:28 +00:00
parent fd5e95971e
commit a1ee06625c
7 changed files with 100 additions and 50 deletions
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29
src/backend/parser/gram.y
View File

@@ -11,7 +11,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.251 2001/09/18 01:59:06 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.252 2001/09/20 14:20:27 petere Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@@ -89,7 +89,6 @@ static void insertSelectOptions(SelectStmt *stmt,
List *sortClause, List *forUpdate,
Node *limitOffset, Node *limitCount);
static Node *makeSetOp(SetOperation op, bool all, Node *larg, Node *rarg);
static bool exprIsNullConstant(Node *arg);
static Node *doNegate(Node *n);
static void doNegateFloat(Value *v);
@@ -4465,29 +4464,7 @@ a_expr: c_expr
| a_expr '>' a_expr
{ $$ = makeA_Expr(OP, ">", $1, $3); }
| a_expr '=' a_expr
{
/*
* Special-case "foo = NULL" and "NULL = foo" for
* compatibility with standards-broken products
* (like Microsoft's). Turn these into IS NULL exprs.
*/
if (exprIsNullConstant($3))
{
NullTest *n = makeNode(NullTest);
n->arg = $1;
n->nulltesttype = IS_NULL;
$$ = (Node *)n;
}
else if (exprIsNullConstant($1))
{
NullTest *n = makeNode(NullTest);
n->arg = $3;
n->nulltesttype = IS_NULL;
$$ = (Node *)n;
}
else
$$ = makeA_Expr(OP, "=", $1, $3);
}
{ $$ = makeA_Expr(OP, "=", $1, $3); }
| a_expr Op a_expr
{ $$ = makeA_Expr(OP, $2, $1, $3); }
@@ -6137,7 +6114,7 @@ Oid param_type(int t)
/*
* Test whether an a_expr is a plain NULL constant or not.
*/
static bool
bool
exprIsNullConstant(Node *arg)
{
if (arg && IsA(arg, A_Const))

40
src/backend/parser/parse_expr.c
View File

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.99 2001/08/09 18:28:17 petere Exp $
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.100 2001/09/20 14:20:27 petere Exp $
*
*-------------------------------------------------------------------------
*/
@@ -34,9 +34,10 @@
int max_expr_depth = DEFAULT_MAX_EXPR_DEPTH;
static int expr_depth_counter = 0;
bool Transform_null_equals = false;
static Node *parser_typecast_constant(Value *expr, TypeName *typename);
static Node *parser_typecast_expression(ParseState *pstate,
Node *expr, TypeName *typename);
@@ -157,14 +158,35 @@ transformExpr(ParseState *pstate, Node *expr, int precedence)
{
case OP:
{
Node *lexpr = transformExpr(pstate,
a->lexpr,
precedence);
Node *rexpr = transformExpr(pstate,
a->rexpr,
precedence);
/*
* Special-case "foo = NULL" and "NULL = foo" for
* compatibility with standards-broken products
* (like Microsoft's). Turn these into IS NULL exprs.
*/
if (Transform_null_equals && strcmp(a->opname, "=")==0
&& (exprIsNullConstant(a->lexpr) || exprIsNullConstant(a->rexpr)))
{
NullTest *n = makeNode(NullTest);
n->nulltesttype = IS_NULL;
result = (Node *) make_op(a->opname, lexpr, rexpr);
if (exprIsNullConstant(a->lexpr))
n->arg = a->rexpr;
else
n->arg = a->lexpr;
result = transformExpr(pstate, n, precedence);
}
else
{
Node *lexpr = transformExpr(pstate,
a->lexpr,
precedence);
Node *rexpr = transformExpr(pstate,
a->rexpr,
precedence);
result = (Node *) make_op(a->opname, lexpr, rexpr);
}
}
break;
case AND: