Re: Please provide examples of rows from

I wrote:
> Yeah, this error message needs some help.  With a function having
> multiple OUT parameters, the prorettype is indeed "record", but
> the specific record type is implied by the OUT parameters so you
> do not need to (and can't) specify it in the query.
> The point of the AS feature is to allow specifying the concrete
> record type for record-returning functions that don't have a
> predefined result record type, like dblink().
> I think this error text was written before we had multiple OUT
> parameters, so it was okay at the time; but now it needs to be
> more precise.

Concretely, perhaps like the attached.  I was unsurprised to find
that this error condition isn't exercised in our regression tests.
I added some coverage, but maybe that's overkill?

            regards, tom lane

diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index b875a50646..a56bd86181 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -1737,16 +1737,46 @@ addRangeTableEntryForFunction(ParseState *pstate,

         /*
          * A coldeflist is required if the function returns RECORD and hasn't
-         * got a predetermined record type, and is prohibited otherwise.
+         * got a predetermined record type, and is prohibited otherwise.  This
+         * can be a bit confusing, so we expend some effort on delivering a
+         * relevant error message.
          */
         if (coldeflist != NIL)
         {
-            if (functypclass != TYPEFUNC_RECORD)
-                ereport(ERROR,
-                        (errcode(ERRCODE_SYNTAX_ERROR),
-                         errmsg("a column definition list is only allowed for functions returning \"record\""),
-                         parser_errposition(pstate,
-                                            exprLocation((Node *) coldeflist))));
+            switch (functypclass)
+            {
+                case TYPEFUNC_RECORD:
+                    /* ok */
+                    break;
+                case TYPEFUNC_COMPOSITE:
+                case TYPEFUNC_COMPOSITE_DOMAIN:
+
+                    /*
+                     * If the function's raw result type is RECORD, we must
+                     * have resolved it using its OUT parameters.  Otherwise,
+                     * it must have a named composite type.
+                     */
+                    if (exprType(funcexpr) == RECORDOID)
+                        ereport(ERROR,
+                                (errcode(ERRCODE_SYNTAX_ERROR),
+                                 errmsg("a column definition list is redundant for a function with OUT parameters"),
+                                 parser_errposition(pstate,
+                                                    exprLocation((Node *) coldeflist))));
+                    else
+                        ereport(ERROR,
+                                (errcode(ERRCODE_SYNTAX_ERROR),
+                                 errmsg("a column definition list is redundant for a function returning a named
compositetype"), 
+                                 parser_errposition(pstate,
+                                                    exprLocation((Node *) coldeflist))));
+                    break;
+                default:
+                    ereport(ERROR,
+                            (errcode(ERRCODE_SYNTAX_ERROR),
+                             errmsg("a column definition list is only allowed for functions returning \"record\""),
+                             parser_errposition(pstate,
+                                                exprLocation((Node *) coldeflist))));
+                    break;
+            }
         }
         else
         {
diff --git a/src/test/regress/expected/rangefuncs.out b/src/test/regress/expected/rangefuncs.out
index 7eced28452..e618aec2eb 100644
--- a/src/test/regress/expected/rangefuncs.out
+++ b/src/test/regress/expected/rangefuncs.out
@@ -2109,6 +2109,19 @@ select * from testrngfunc();
  7.136178 | 7.14
 (1 row)

+-- Check a couple of error cases while we're here
+select * from testrngfunc() as t(f1 int8,f2 int8);  -- fail, composite result
+ERROR:  a column definition list is redundant for a function returning a named composite type
+LINE 1: select * from testrngfunc() as t(f1 int8,f2 int8);
+                                         ^
+select * from pg_get_keywords() as t(f1 int8,f2 int8);  -- fail, OUT params
+ERROR:  a column definition list is redundant for a function with OUT parameters
+LINE 1: select * from pg_get_keywords() as t(f1 int8,f2 int8);
+                                             ^
+select * from sin(3) as t(f1 int8,f2 int8);  -- fail, scalar result type
+ERROR:  a column definition list is only allowed for functions returning "record"
+LINE 1: select * from sin(3) as t(f1 int8,f2 int8);
+                                  ^
 drop type rngfunc_type cascade;
 NOTICE:  drop cascades to function testrngfunc()
 --
diff --git a/src/test/regress/sql/rangefuncs.sql b/src/test/regress/sql/rangefuncs.sql
index ae3119a959..5f41cb2d8d 100644
--- a/src/test/regress/sql/rangefuncs.sql
+++ b/src/test/regress/sql/rangefuncs.sql
@@ -629,6 +629,11 @@ explain (verbose, costs off)
 select * from testrngfunc();
 select * from testrngfunc();

+-- Check a couple of error cases while we're here
+select * from testrngfunc() as t(f1 int8,f2 int8);  -- fail, composite result
+select * from pg_get_keywords() as t(f1 int8,f2 int8);  -- fail, OUT params
+select * from sin(3) as t(f1 int8,f2 int8);  -- fail, scalar result type
+
 drop type rngfunc_type cascade;

 --