Re: PostgreSQL 8.0.6 crash - Mailing list pgsql-hackers

From Mark Woodward
Subject Re: PostgreSQL 8.0.6 crash
Date
Msg-id 16528.24.91.171.78.1139509705.squirrel@mail.mohawksoft.com
Whole thread Raw
In response to Re: PostgreSQL 8.0.6 crash  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: PostgreSQL 8.0.6 crash  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
> "Mark Woodward" <pgsql@mohawksoft.com> writes:
>> I think it is still a bug. While it may manifest itself as a pg crash on
>> Linux because of a feature with which you have issue, the fact remains
>> that PG is exeeding its working memory limit.
>
> The problem is that *we have no way to know what that limit is* ---
> short of exceeding it and being summarily killed.  (BTW, the kernel
> doesn't know what the limit is either.)  There is simply not any way
> to operate robustly under the OOM-kill regime.

No, you misunderstand what I said, the "working memory" as defined in
postgresql.conf. I don't care about the OS debate.

>
> While I'll certainly acknowledge that it'd be nice if hashagg had
> spill-to-disk capability, that wouldn't alter the fundamental fact that
> if you want reliable behavior you MUST turn off OOM kill.  There is not
> anything we can do at the database level to work around that kernel-level
> misdesign.

Again, regardless of OS used, hashagg will exceed "working memory" as
defined in postgresql.conf.

At issue is would a lack of ANALYZE justify this behavior? If so, it
should be documented.



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