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Postgres FD Implementation
Commit 117fa25a authored by Tom Lane's avatar Tom Lane
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Clean up grammar's handling of NULL in expressions: a_expr_or_null is 

gone, replaced by plain a_expr.  The few places where we needed to
distinguish NULL from a_expr are now handled by tests inside the actions
rather than by separate productions.  This allows us to accept queries
like 'SELECT 1 + NULL' without requiring parentheses around the NULL.
parent e8be8ffa
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Showing with 66 additions and 61 deletions
src/backend/parser/gram.y
View file @ 117fa25a
......@@ -11,7 +11,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.153 2000/03/01 05:18:19 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.154 2000/03/12 00:39:52 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
......@@ -77,6 +77,7 @@ static Node *makeTypeCast(Node *arg, TypeName *typename);
static Node *makeRowExpr(char *opr, List *largs, List *rargs);
static void mapTargetColumns(List *source, List *target);
static void param_type_init(Oid *typev, int nargs);
static bool exprIsNullConstant(Node *arg);
static Node *doNegate(Node *n);
static void doNegateFloat(Value *v);
......@@ -229,7 +230,7 @@ static void doNegateFloat(Value *v);
%type <node> columnDef
%type <defelt> def_elem
%type <node> def_arg, columnElem, where_clause,
a_expr, a_expr_or_null, b_expr, c_expr, AexprConst,
a_expr, b_expr, c_expr, AexprConst,
in_expr, having_clause
%type <list> row_descriptor, row_list, in_expr_nodes
%type <node> row_expr
......@@ -873,8 +874,14 @@ AlterTableStmt:
;
alter_column_action:
SET DEFAULT a_expr { $$ = $3; }
| SET DEFAULT NULL_P { $$ = NULL; }
SET DEFAULT a_expr
{
/* Treat SET DEFAULT NULL the same as DROP DEFAULT */
if (exprIsNullConstant($3))
$$ = NULL;
else
$$ = $3;
}
| DROP DEFAULT { $$ = NULL; }
;
......@@ -1155,22 +1162,20 @@ ColConstraintElem:
n->keys = NULL;
$$ = (Node *)n;
}
| DEFAULT NULL_P
{
Constraint *n = makeNode(Constraint);
n->contype = CONSTR_DEFAULT;
n->name = NULL;
n->raw_expr = NULL;
n->cooked_expr = NULL;
n->keys = NULL;
$$ = (Node *)n;
}
| DEFAULT b_expr
{
Constraint *n = makeNode(Constraint);
n->contype = CONSTR_DEFAULT;
n->name = NULL;
n->raw_expr = $2;
if (exprIsNullConstant($2))
{
/* DEFAULT NULL should be reported as empty expr */
n->raw_expr = NULL;
}
else
{
n->raw_expr = $2;
}
n->cooked_expr = NULL;
n->keys = NULL;
$$ = (Node *)n;
......@@ -4017,16 +4022,6 @@ opt_interval: datetime { $$ = lcons($1, NIL); }
*
*****************************************************************************/
a_expr_or_null: a_expr
{ $$ = $1; }
| NULL_P
{
A_Const *n = makeNode(A_Const);
n->val.type = T_Null;
$$ = (Node *)n;
}
;
/* Expressions using row descriptors
* Define row_descriptor to allow yacc to break the reduce/reduce conflict
* with singleton expressions.
......@@ -4137,17 +4132,6 @@ a_expr: c_expr
{ $$ = $1; }
| a_expr TYPECAST Typename
{ $$ = makeTypeCast($1, $3); }
/*
* Can't collapse this into prior rule by using a_expr_or_null;
* that creates reduce/reduce conflicts. Grumble.
*/
| NULL_P TYPECAST Typename
{
A_Const *n = makeNode(A_Const);
n->val.type = T_Null;
n->typename = $3;
$$ = (Node *)n;
}
/*
* These operators must be called out explicitly in order to make use
* of yacc/bison's automatic operator-precedence handling. All other
......@@ -4193,15 +4177,20 @@ a_expr: c_expr
{ $$ = makeA_Expr(OP, "<", $1, $3); }
| a_expr '>' a_expr
{ $$ = makeA_Expr(OP, ">", $1, $3); }
| a_expr '=' NULL_P
{ $$ = makeA_Expr(ISNULL, NULL, $1, NULL); }
/* We allow this for standards-broken SQL products, like MS stuff */
| NULL_P '=' a_expr
{ $$ = makeA_Expr(ISNULL, NULL, $3, NULL); }
| a_expr '=' a_expr
{ $$ = makeA_Expr(OP, "=", $1, $3); }
{
/*
* Special-case "foo = NULL" and "NULL = foo" for
* compatibility with standards-broken products
* (like Microsoft's). Turn these into IS NULL exprs.
*/
if (exprIsNullConstant($3))
$$ = makeA_Expr(ISNULL, NULL, $1, NULL);
else if (exprIsNullConstant($1))
$$ = makeA_Expr(ISNULL, NULL, $3, NULL);
else
$$ = makeA_Expr(OP, "=", $1, $3);
}
| a_expr Op a_expr
{ $$ = makeA_Expr(OP, $2, $1, $3); }
......@@ -4360,7 +4349,7 @@ a_expr: c_expr
*
* b_expr is a subset of the complete expression syntax defined by a_expr.
*
* Presently, AND, NOT, IS, IN, and NULL are the a_expr keywords that would
* Presently, AND, NOT, IS, and IN are the a_expr keywords that would
* cause trouble in the places where b_expr is used. For simplicity, we
* just eliminate all the boolean-keyword-operator productions from b_expr.
*/
......@@ -4368,13 +4357,6 @@ b_expr: c_expr
{ $$ = $1; }
| b_expr TYPECAST Typename
{ $$ = makeTypeCast($1, $3); }
| NULL_P TYPECAST Typename
{
A_Const *n = makeNode(A_Const);
n->val.type = T_Null;
n->typename = $3;
$$ = (Node *)n;
}
| '-' b_expr %prec UMINUS
{ $$ = doNegate($2); }
| '%' b_expr
......@@ -4442,9 +4424,9 @@ c_expr: attr
}
| AexprConst
{ $$ = $1; }
| '(' a_expr_or_null ')'
| '(' a_expr ')'
{ $$ = $2; }
| CAST '(' a_expr_or_null AS Typename ')'
| CAST '(' a_expr AS Typename ')'
{ $$ = makeTypeCast($3, $5); }
| case_expr
{ $$ = $1; }
......@@ -4788,9 +4770,9 @@ opt_indirection: '[' a_expr ']' opt_indirection
{ $$ = NIL; }
;
expr_list: a_expr_or_null
expr_list: a_expr
{ $$ = lcons($1, NIL); }
| expr_list ',' a_expr_or_null
| expr_list ',' a_expr
{ $$ = lappend($1, $3); }
| expr_list USING a_expr
{ $$ = lappend($1, $3); }
......@@ -4928,7 +4910,7 @@ when_clause_list: when_clause_list when_clause
{ $$ = lcons($1, NIL); }
;
when_clause: WHEN a_expr THEN a_expr_or_null
when_clause: WHEN a_expr THEN a_expr
{
CaseWhen *w = makeNode(CaseWhen);
w->expr = $2;
......@@ -4937,7 +4919,7 @@ when_clause: WHEN a_expr THEN a_expr_or_null
}
;
case_default: ELSE a_expr_or_null { $$ = $2; }
case_default: ELSE a_expr { $$ = $2; }
| /*EMPTY*/ { $$ = NULL; }
;
......@@ -4989,14 +4971,14 @@ target_list: target_list ',' target_el
;
/* AS is not optional because shift/red conflict with unary ops */
target_el: a_expr_or_null AS ColLabel
target_el: a_expr AS ColLabel
{
$$ = makeNode(ResTarget);
$$->name = $3;
$$->indirection = NULL;
$$->val = (Node *)$1;
}
| a_expr_or_null
| a_expr
{
$$ = makeNode(ResTarget);
$$->name = NULL;
......@@ -5037,7 +5019,7 @@ update_target_list: update_target_list ',' update_target_el
{ $$ = lcons($1, NIL); }
;
update_target_el: ColId opt_indirection '=' a_expr_or_null
update_target_el: ColId opt_indirection '=' a_expr
{
$$ = makeNode(ResTarget);
$$->name = $1;
......@@ -5142,6 +5124,12 @@ AexprConst: Iconst
n->typename->typmod = -1;
$$ = (Node *)n;
}
| NULL_P
{
A_Const *n = makeNode(A_Const);
n->val.type = T_Null;
$$ = (Node *)n;
}
;
ParamNo: PARAM opt_indirection
......@@ -5532,6 +5520,23 @@ Oid param_type(int t)
return param_type_info[t - 1];
}
/*
* Test whether an a_expr is a plain NULL constant or not.
*/
static bool
exprIsNullConstant(Node *arg)
{
if (arg && IsA(arg, A_Const))
{
A_Const *con = (A_Const *) arg;
if (con->val.type == T_Null &&
con->typename == NULL)
return true;
}
return false;
}
/*
* doNegate --- handle negation of a numeric constant.
*
......
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