Re: Partitions and work_mem?

On Wed, Oct 15, 2014 at 1:36 PM, Igor Neyman <ineyman(at)perceptron(dot)com> wrote:

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> *From:* Dave Johansen [mailto:davejohansen(at)gmail(dot)com]
> *Sent:* Wednesday, October 15, 2014 4:20 PM
> *To:* Igor Neyman
> *Cc:* Josh Berkus; pgsql-performance
> *Subject:* Re: [PERFORM] Partitions and work_mem?
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> On Wed, Oct 15, 2014 at 1:08 PM, Igor Neyman <ineyman(at)perceptron(dot)com>
> wrote:
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> *From:* pgsql-performance-owner(at)postgresql(dot)org [mailto:
> pgsql-performance-owner(at)postgresql(dot)org] *On Behalf Of *Dave Johansen
> *Sent:* Wednesday, October 15, 2014 4:05 PM
> *To:* Josh Berkus
> *Cc:* pgsql-performance
> *Subject:* Re: [PERFORM] Partitions and work_mem?
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> On Wed, Oct 15, 2014 at 10:10 AM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
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> On 10/14/2014 10:08 AM, Dave Johansen wrote:
> > I'm running Postgres 8.4 on RHEL 6 64-bit and I had a question about how
> > work_mem and partitions interact.
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> > https://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server#work_mem
> > The above wiki states that "if a query involves doing merge sorts of 8
> > tables, that requires 8 times work_mem." If I have a table that is
> > partitioned does each partition count as a "table" and get its on
> work_mem?
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> In theory, this could happen. In practice, based on tests I did at Sun
> with DBT3 and 8.3, no backend ever used more than 3X work_mem. This is
> partly because the level of parallelism in postgres is extremely
> limited, so we can't actually sort 8 partitions at the same time.
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> Thanks for the feedback. That's very helpful.
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> BTW, 8.4 is EOL. Maybe time to upgrade?
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> RHEL 6 isn't EOLed and we're working on moving to RHEL 7 but it's a slow
> process that will probably take quite a bit of time, if it ever happens.
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> Postgres 8.4 is EOL (RHEL).
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> Sorry I don't understand what you mean by that. My understanding is that
> RedHat maintains fixes for security and other major issues for packages
> that have been EOLed. Are you implying that that's not the case? Or
> something else?
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> I don’t think that RedHat can maintain Postgres version which was EOLed.
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> Postgres 8.4 is not supported by PostgreSQL community.
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This conversation has probably become a bit off topic, but my understanding
is that what you're paying RedHat for is a stable platform for a long
period of time. That means creating/backporting of fixes for security and
other critical issues for packages that have been EOLed.

Assuming the above is true, (which I beleve to be the case
https://access.redhat.com/support/policy/updates/errata ), I don't see what
would prevent RedHat from making a patch and applying it to the latest 8.4
release to resolve any newly discovered issues. Isn't that the whole point
of open source and RedHat being able to do with the code what it wishes as
long as it meets the requirements of the license? So are you claiming that
RedHat doesn't/won't do this? Is incapable of doing this? Or am I missing
something?