targetlist functions part 1 (was [HACKERS] targetlist functions proposals)

Joe Conway wrote:
> =================================================================
> User interface proposal for multi-row function targetlist entries
> =================================================================
> 1. Only one targetlist entry may return a set.
> 2. Each targetlist item (other than the set returning one) is
> repeated for each item in the returned set.
>

Having gotten no objections (actually, no response at all), I can only assume
no one had heartburn with this change. The attached patch covers the first of
the two proposals, i.e. restricting the target list to only one set returning
function.

It compiles cleanly, and passes all regression tests. If there are no
objections, please apply.

Any suggestions on where this should be documented (other than maybe sql-select)?

Thanks,

Joe

p.s. Here's what the previous example now looks like:
CREATE TABLE bar(f1 int, f2 text, f3 int);
INSERT INTO bar VALUES(1, 'Hello', 42);
INSERT INTO bar VALUES(2, 'Happy', 45);

CREATE TABLE foo(a int, b text);
INSERT INTO foo VALUES(42, 'World');
INSERT INTO foo VALUES(42, 'Everyone');
INSERT INTO foo VALUES(45, 'Birthday');
INSERT INTO foo VALUES(45, 'New Year');

CREATE TABLE foo2(a int, b text);
INSERT INTO foo2 VALUES(42, '!!!!');
INSERT INTO foo2 VALUES(42, '????');
INSERT INTO foo2 VALUES(42, '####');
INSERT INTO foo2 VALUES(45, '$$$$');

CREATE OR REPLACE FUNCTION getfoo(int) RETURNS SETOF text AS '
SELECT b FROM foo WHERE a = $1
' language 'sql';

CREATE OR REPLACE FUNCTION getfoo2(int) RETURNS SETOF text AS '
SELECT b FROM foo2 WHERE a = $1
' language 'sql';

regression=# SELECT f1, f2, getfoo(f3) AS f4 FROM bar;
f1 | f2 | f4
----+-------+----------
1 | Hello | World
1 | Hello | Everyone
2 | Happy | Birthday
2 | Happy | New Year
(4 rows)

regression=# SELECT f1, f2, getfoo(f3) AS f4, getfoo2(f3) AS f5 FROM bar;
ERROR: Only one target list entry may return a set result