BUG #2750: information_schema broken with primary and foreign key on the same column

The following bug has been logged online:

Bug reference: 2750
Logged by: Stephen haberman
Email address: stephen(at)exigencecorp(dot)com
PostgreSQL version: 8.2 beta 3
Operating system: win32
Description: information_schema broken with primary and foreign key
on the same column
Details:

Just tried postgresql 8.2 beta 3 and it is missing a patch I had sent to
pgsql-patches after trying 8.2 beta 2 a few weeks ago.

The information_schema `position_in_unique_constraint` is broken when a
column has both a primary key and a foreign key. Both constraints match in
the `SELECT a FROM generate_series` and caused a "subquery returns multiple
results for an expression" error.

(Or something like that--I don't have the exact error message handy.)

This patch fixes it:

--- information_schema-original.sql Tue Oct 24 11:10:16 2006
+++ information_schema.sql Fri Oct 27 02:24:52 2006
@@ -928,6 +928,7 @@
(SELECT a FROM generate_series(1, array_upper(ss.confkey,1))
a) AS foo
WHERE conrelid = ss.confrelid
AND conkey[foo.a] = ss.confkey[(ss.x).n]
+ AND contype = 'f'
) AS position_in_unique_constraint
FROM pg_attribute a,
(SELECT r.oid, r.relname, nc.nspname AS nc_nspname,