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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.
This commit is contained in:
Tom Lane
parent
e8be8ffaf0
commit
117fa25ae1
@ -11,7 +11,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.153 2000/03/01 05:18:19 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.154 2000/03/12 00:39:52 tgl Exp $
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*
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* HISTORY
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* AUTHOR DATE MAJOR EVENT
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@ -77,6 +77,7 @@ static Node *makeTypeCast(Node *arg, TypeName *typename);
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static Node *makeRowExpr(char *opr, List *largs, List *rargs);
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static void mapTargetColumns(List *source, List *target);
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static void param_type_init(Oid *typev, int nargs);
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static bool exprIsNullConstant(Node *arg);
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static Node *doNegate(Node *n);
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static void doNegateFloat(Value *v);
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@ -229,7 +230,7 @@ static void doNegateFloat(Value *v);
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%type <node> columnDef
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%type <defelt> def_elem
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%type <node> def_arg, columnElem, where_clause,
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a_expr, a_expr_or_null, b_expr, c_expr, AexprConst,
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a_expr, b_expr, c_expr, AexprConst,
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in_expr, having_clause
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%type <list> row_descriptor, row_list, in_expr_nodes
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%type <node> row_expr
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@ -873,8 +874,14 @@ AlterTableStmt:
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;
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alter_column_action:
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SET DEFAULT a_expr { $$ = $3; }
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| SET DEFAULT NULL_P { $$ = NULL; }
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SET DEFAULT a_expr
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{
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/* Treat SET DEFAULT NULL the same as DROP DEFAULT */
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if (exprIsNullConstant($3))
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$$ = NULL;
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else
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$$ = $3;
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}
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| DROP DEFAULT { $$ = NULL; }
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;
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@ -1155,22 +1162,20 @@ ColConstraintElem:
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n->keys = NULL;
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$$ = (Node *)n;
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}
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| DEFAULT NULL_P
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{
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Constraint *n = makeNode(Constraint);
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n->contype = CONSTR_DEFAULT;
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n->name = NULL;
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n->raw_expr = NULL;
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n->cooked_expr = NULL;
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n->keys = NULL;
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$$ = (Node *)n;
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}
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| DEFAULT b_expr
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{
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Constraint *n = makeNode(Constraint);
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n->contype = CONSTR_DEFAULT;
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n->name = NULL;
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n->raw_expr = $2;
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if (exprIsNullConstant($2))
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{
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/* DEFAULT NULL should be reported as empty expr */
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n->raw_expr = NULL;
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}
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else
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{
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n->raw_expr = $2;
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}
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n->cooked_expr = NULL;
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n->keys = NULL;
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$$ = (Node *)n;
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@ -4017,16 +4022,6 @@ opt_interval: datetime { $$ = lcons($1, NIL); }
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*
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*****************************************************************************/
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a_expr_or_null: a_expr
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{ $$ = $1; }
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| NULL_P
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{
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A_Const *n = makeNode(A_Const);
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n->val.type = T_Null;
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$$ = (Node *)n;
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}
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;
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/* Expressions using row descriptors
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* Define row_descriptor to allow yacc to break the reduce/reduce conflict
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* with singleton expressions.
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@ -4137,17 +4132,6 @@ a_expr: c_expr
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{ $$ = $1; }
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| a_expr TYPECAST Typename
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{ $$ = makeTypeCast($1, $3); }
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/*
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* Can't collapse this into prior rule by using a_expr_or_null;
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* that creates reduce/reduce conflicts. Grumble.
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*/
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| NULL_P TYPECAST Typename
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{
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A_Const *n = makeNode(A_Const);
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n->val.type = T_Null;
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n->typename = $3;
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$$ = (Node *)n;
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}
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/*
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* These operators must be called out explicitly in order to make use
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* of yacc/bison's automatic operator-precedence handling. All other
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@ -4193,15 +4177,20 @@ a_expr: c_expr
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{ $$ = makeA_Expr(OP, "<", $1, $3); }
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| a_expr '>' a_expr
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{ $$ = makeA_Expr(OP, ">", $1, $3); }
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| a_expr '=' NULL_P
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{ $$ = makeA_Expr(ISNULL, NULL, $1, NULL); }
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/* We allow this for standards-broken SQL products, like MS stuff */
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| NULL_P '=' a_expr
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{ $$ = makeA_Expr(ISNULL, NULL, $3, NULL); }
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| a_expr '=' a_expr
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{ $$ = makeA_Expr(OP, "=", $1, $3); }
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{
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/*
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* Special-case "foo = NULL" and "NULL = foo" for
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* compatibility with standards-broken products
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* (like Microsoft's). Turn these into IS NULL exprs.
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*/
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if (exprIsNullConstant($3))
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$$ = makeA_Expr(ISNULL, NULL, $1, NULL);
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else if (exprIsNullConstant($1))
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$$ = makeA_Expr(ISNULL, NULL, $3, NULL);
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else
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$$ = makeA_Expr(OP, "=", $1, $3);
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}
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| a_expr Op a_expr
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{ $$ = makeA_Expr(OP, $2, $1, $3); }
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@ -4360,7 +4349,7 @@ a_expr: c_expr
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*
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* b_expr is a subset of the complete expression syntax defined by a_expr.
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*
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* Presently, AND, NOT, IS, IN, and NULL are the a_expr keywords that would
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* Presently, AND, NOT, IS, and IN are the a_expr keywords that would
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* cause trouble in the places where b_expr is used. For simplicity, we
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* just eliminate all the boolean-keyword-operator productions from b_expr.
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*/
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@ -4368,13 +4357,6 @@ b_expr: c_expr
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{ $$ = $1; }
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| b_expr TYPECAST Typename
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{ $$ = makeTypeCast($1, $3); }
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| NULL_P TYPECAST Typename
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{
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A_Const *n = makeNode(A_Const);
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n->val.type = T_Null;
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n->typename = $3;
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$$ = (Node *)n;
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}
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| '-' b_expr %prec UMINUS
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{ $$ = doNegate($2); }
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| '%' b_expr
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@ -4442,9 +4424,9 @@ c_expr: attr
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}
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| AexprConst
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{ $$ = $1; }
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| '(' a_expr_or_null ')'
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| '(' a_expr ')'
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{ $$ = $2; }
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| CAST '(' a_expr_or_null AS Typename ')'
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| CAST '(' a_expr AS Typename ')'
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{ $$ = makeTypeCast($3, $5); }
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| case_expr
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{ $$ = $1; }
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@ -4788,9 +4770,9 @@ opt_indirection: '[' a_expr ']' opt_indirection
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{ $$ = NIL; }
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;
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expr_list: a_expr_or_null
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expr_list: a_expr
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{ $$ = lcons($1, NIL); }
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| expr_list ',' a_expr_or_null
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| expr_list ',' a_expr
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{ $$ = lappend($1, $3); }
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| expr_list USING a_expr
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{ $$ = lappend($1, $3); }
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@ -4928,7 +4910,7 @@ when_clause_list: when_clause_list when_clause
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{ $$ = lcons($1, NIL); }
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;
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when_clause: WHEN a_expr THEN a_expr_or_null
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when_clause: WHEN a_expr THEN a_expr
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{
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CaseWhen *w = makeNode(CaseWhen);
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w->expr = $2;
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@ -4937,7 +4919,7 @@ when_clause: WHEN a_expr THEN a_expr_or_null
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}
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;
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case_default: ELSE a_expr_or_null { $$ = $2; }
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case_default: ELSE a_expr { $$ = $2; }
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| /*EMPTY*/ { $$ = NULL; }
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;
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@ -4989,14 +4971,14 @@ target_list: target_list ',' target_el
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;
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/* AS is not optional because shift/red conflict with unary ops */
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target_el: a_expr_or_null AS ColLabel
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target_el: a_expr AS ColLabel
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{
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$$ = makeNode(ResTarget);
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$$->name = $3;
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$$->indirection = NULL;
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$$->val = (Node *)$1;
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}
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| a_expr_or_null
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| a_expr
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{
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$$ = makeNode(ResTarget);
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$$->name = NULL;
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@ -5037,7 +5019,7 @@ update_target_list: update_target_list ',' update_target_el
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{ $$ = lcons($1, NIL); }
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;
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update_target_el: ColId opt_indirection '=' a_expr_or_null
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update_target_el: ColId opt_indirection '=' a_expr
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{
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$$ = makeNode(ResTarget);
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$$->name = $1;
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@ -5142,6 +5124,12 @@ AexprConst: Iconst
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n->typename->typmod = -1;
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$$ = (Node *)n;
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}
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| NULL_P
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{
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A_Const *n = makeNode(A_Const);
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n->val.type = T_Null;
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$$ = (Node *)n;
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}
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;
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ParamNo: PARAM opt_indirection
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@ -5532,6 +5520,23 @@ Oid param_type(int t)
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return param_type_info[t - 1];
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}
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/*
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* Test whether an a_expr is a plain NULL constant or not.
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*/
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static bool
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exprIsNullConstant(Node *arg)
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{
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if (arg && IsA(arg, A_Const))
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{
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A_Const *con = (A_Const *) arg;
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if (con->val.type == T_Null &&
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con->typename == NULL)
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return true;
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}
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return false;
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}
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/*
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* doNegate --- handle negation of a numeric constant.
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*
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