BUG #9430: Strange error during pg_dump with concurrent alter table working

The following bug has been logged on the website:

Bug reference: 9430
Logged by: Maxim Boguk
Email address: maxim(dot)boguk(at)gmail(dot)com
PostgreSQL version: 9.2.7
Operating system: Linux
Description:

Hi,

Today during performing database schema migration, I got strange error from
concurrently working
pg_dump -F p -s:

pg_dump: [archiver (db)] query failed: ERROR: cache lookup failed for
constraint 18543
pg_dump: [archiver (db)] query was: SELECT tableoid, oid, conname,
pg_catalog.pg_get_constraintdef(oid) AS consrc, conislocal, convalidated
FROM pg_catalog.pg_constraint WHERE conrelid = '26756'::pg_catalog.oid
AND contype = 'c' ORDER BY conname

This constraint was defined as:
[local]:5432 postgres(at)sports=# SELECT tableoid, oid, conname,
pg_catalog.pg_get_constraintdef(oid) AS consrc, conislocal, convalidated
FROM pg_catalog.pg_constraint WHERE conrelid = '26756'::pg_catalog.oid
AND contype = 'c' ORDER BY conname;
-[ RECORD 1
]+--------------------------------------------------------------
tableoid | 2606
oid | 97238286
conname | fb_rate_account_sport_user_id_cookie_check
consrc | CHECK (((sport_user_id IS NOT NULL) OR (cookie IS NOT
NULL)))
conislocal | t
convalidated | t

Concurrent ALTER command:
/*65851105*/alter table stat.fb_rate_account alter column sport_user_id type
int8;

I will try create self-containing test case in few hours.

Kind Regards,
Maksym