Tom Lane írta:
Andrew Dunstan <[EMAIL PROTECTED]> writes:
Tom Lane wrote:
So I think attaching a precedence to the GENERATED keyword is dangerous.


Especially when we have a good workaround which would just require use of () around certain postfix-operator expressions.

Yeah, I'm leaning to the idea that removing postfix operators from
b_expr is the least bad solution.

One thing that would have to be looked at is the rules in ruleutils.c
for suppressing "unnecessary" parentheses when reverse-listing
parsetrees.  It might be safest to just never suppress them around a
postfix operator.

                        regards, tom lane

You mean something like this?

-----------------------------------------------------
***************
*** 4138,4157 ****
       Oid                     opno = expr->opno;
       List       *args = expr->args;

-       if (!PRETTY_PAREN(context))
-               appendStringInfoChar(buf, '(');
       if (list_length(args) == 2)
       {
               /* binary operator */
               Node       *arg1 = (Node *) linitial(args);
               Node       *arg2 = (Node *) lsecond(args);

               get_rule_expr_paren(arg1, context, true, (Node *) expr);
               appendStringInfo(buf, " %s ",
generate_operator_name(opno, exprType(arg1), exprType(arg2)));
               get_rule_expr_paren(arg2, context, true, (Node *) expr);
       }
       else
       {
--- 4095,4118 ----
       Oid                     opno = expr->opno;
       List       *args = expr->args;

       if (list_length(args) == 2)
       {
               /* binary operator */
               Node       *arg1 = (Node *) linitial(args);
               Node       *arg2 = (Node *) lsecond(args);

+               if (!PRETTY_PAREN(context))
+                       appendStringInfoChar(buf, '(');
+
               get_rule_expr_paren(arg1, context, true, (Node *) expr);
               appendStringInfo(buf, " %s ",
generate_operator_name(opno, exprType(arg1), exprType(arg2)));
               get_rule_expr_paren(arg2, context, true, (Node *) expr);
+
+               if (!PRETTY_PAREN(context))
+                       appendStringInfoChar(buf, ')');
       }
       else
       {
***************
*** 4169,4194 ****
               switch (optup->oprkind)
               {
                       case 'l':
                               appendStringInfo(buf, "%s ",
generate_operator_name(opno, InvalidOid, exprType(arg))); get_rule_expr_paren(arg, context, true, (Node *) expr);
                               break;
                       case 'r':
get_rule_expr_paren(arg, context, true, (Node *) expr);
                               appendStringInfo(buf, " %s",
generate_operator_name(opno, exprType(arg), InvalidOid));
                               break;
                       default:
elog(ERROR, "bogus oprkind: %d", optup->oprkind);
               }
               ReleaseSysCache(tp);
       }
-       if (!PRETTY_PAREN(context))
-               appendStringInfoChar(buf, ')');
 }

 /*
--- 4130,4159 ----
               switch (optup->oprkind)
               {
                       case 'l':
+                               if (!PRETTY_PAREN(context))
+                                       appendStringInfoChar(buf, '(');
                               appendStringInfo(buf, "%s ",
generate_operator_name(opno, InvalidOid, exprType(arg))); get_rule_expr_paren(arg, context, true, (Node *) expr);
+                               if (!PRETTY_PAREN(context))
+                                       appendStringInfoChar(buf, ')');
                               break;
                       case 'r':
+                               appendStringInfoChar(buf, '(');
get_rule_expr_paren(arg, context, true, (Node *) expr);
                               appendStringInfo(buf, " %s",
generate_operator_name(opno, exprType(arg), InvalidOid));
+                               appendStringInfoChar(buf, ')');
                               break;
                       default:
elog(ERROR, "bogus oprkind: %d", optup->oprkind);
               }
               ReleaseSysCache(tp);
       }
 }

 /*
-----------------------------------------------------

It seems to work:

-----------------------------------------------------
$ psql
Welcome to psql 8.3devel, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
      \h for help with SQL commands
      \? for help with psql commands
      \g or terminate with semicolon to execute query
      \q to quit

zozo=# create table t1 (i integer default 5! generated always as identity primary key, t text not null unique);
ERROR:  syntax error at or near "always"
LINE 1: create table t1 (i integer default 5! generated always as id...
                                                       ^
zozo=# create table t1 (i integer default (5!) generated always as identity primary key, t text not null unique); NOTICE: CREATE TABLE will create implicit sequence "t1_i_seq" for serial column "t1.i"
ERROR:  multiple default values specified for column "i" of table "t1"
zozo=# create table t1 (i integer default (5!) primary key, t text not null unique); NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey" for table "t1" NOTICE: CREATE TABLE / UNIQUE will create implicit index "t1_t_key" for table "t1"
CREATE TABLE
zozo=# \d t1
                 Table "public.t1"
Column | Type | Modifiers --------+---------+----------------------------------
i      | integer | not null default ((5)::bigint !)
t      | text    | not null
Indexes:
   "t1_pkey" PRIMARY KEY, btree (i)
   "t1_t_key" UNIQUE, btree (t)

zozo=# \q
$ pg_dump
...
--
-- Name: t1; Type: TABLE; Schema: public; Owner: zozo; Tablespace:
--

CREATE TABLE t1 (
   i integer DEFAULT ((5)::bigint !) NOT NULL,
   t text NOT NULL
);

...

--
-- PostgreSQL database dump complete
--
-----------------------------------------------------

So, if I send the patch again (POSTFIXOP deleted from b_expr)
with the above added, will it get accepted?

Best regards,
Zoltán Böszörményi

--
----------------------------------
Zoltán Böszörményi
Cybertec Geschwinde & Schönig GmbH
http://www.postgresql.at/


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