Re: Getting "cache lookup failed for aggregate" error

Patrick Krecker <patrick(at)judicata(dot)com> writes:
> Hello everyone -- We received a strange error today on our production write
> master. During a routine maintenance script, we got the following error:

> "ERROR: cache lookup failed for aggregate 5953992"

> I think I found the culprit. We have a cron script that (among other
> things) recreates the aggregate function array_cat_aggregate()once every
> minute.

Um. Why's it do that?

> My guess is that a) transactions do not guarantee a snapshot of
> custom functions and b) we got unlucky and the aggregate was deleted during
> the execution of the UPDATE.

Yeah, there's no guarantee that dropping the aggregate wouldn't leave a
window for this type of failure.

9.4 might be a little better about this because it doesn't use SnapshotNow
for catalog fetches anymore, but I think you'd still be at some risk.

> Here is the query that produced the error:

It'd be more interesting to see what the cron script was doing to the
aggregate definition.

regards, tom lane