Re: Postmaster holding unlinked files for pg_largeobject table

Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Excerpts from Kevin Grittner's message of lun jun 06 11:58:51 -0400 2011:
>> Alvaro Herrera <alvherre(at)commandprompt(dot)com> wrote:
>>> What we found out after more careful investigation is that the
>>> file is kept open by a backend connected to a different database.
>>> I have a suspicion that what happened here is that this backend
>>> was forced to flush out a page from shared buffers to read some
>>> other page; and it was forced to do a fsync of this file. And
>>> then it forgets to close the file descriptor.

It doesn't "forget" to close the descriptor; it intentionally keeps it
for possible further use.

>> This sounds vaguely similar to what I found with WAL files being
>> held open for days after they were deleted by read-only backends:
>> http://archives.postgresql.org/message-id/15412.1259630304@sss.pgh.pa.us
>> I mention it only because there might be one place to fix both....

> Hmm interesting. I don't think the placement suggested by Tom would be
> useful, because the Zabbix backends are particularly busy all the time,
> so they wouldn't run ProcessCatchupEvent at all.

Yeah, I wasn't that thrilled with the suggestion either. But we can't
just have backends constantly closing every open FD they hold, or
performance will suffer. I don't see any very good place to do this...

regards, tom lane