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.boguk@gmail.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@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