Re: ERROR: cache lookup failed for relation X

raghavendra t <raagavendra(dot)rao(at)gmail(dot)com> writes:
> I am facing the error "cache lookup failed for relation X" in Postgres-8.4.2
> [ when dropping the same table concurrently in two sessions ]
> Could plese tell me, why this is generated and what is the cause.

From the perspective of session B, the table disappeared after it had
already found the table in the catalogs and obtained a lock on it.
This is not readily distinguishable from a serious problem such as
catalog corruption. While we could play dumb and just issue a
"table does not exist" message as though we'd never found it in the
catalog at all, that behavior could mask real problems, so it seems
better to not try to hide that something unusual happened.

In general I would say that an application that is trying to do this
has got its own problems anyway --- how do you know which version of
the table you're dropping, and that that's the right thing?

regards, tom lane