Re: Query Plans on Slaves

We're still considering this architecture - so I don't have any plans.

My question is, does the ANALYZE command, which is only executed on the
master, mean that the statistics / plans that are used on the master are
ALSO used on the slaves? OR .... does the slave create it's own plan?

I would anticipate very different plans between the two machines, and
different postgresql.conf settings as well.

I would *want* different query plans between the two. Is that possible?

On Sun, Nov 9, 2014 at 8:50 PM, Tatsuo Ishii <ishii(at)postgresql(dot)org> wrote:

> > Hi all!
> >
> > We're working on our architecture for our next set of systems, and we
> > normally have a simple master/slave with wal shipping and hot_standby set
> > up, with pgpool sitting in front of both to do load balancing.
> >
> > However, one piece I'm very confused about is the query plans on the
> slave
> > server.
> >
> > Let's pretend we have a master server with:
> > (2) E5-2660 CPU's
> > (4) S3700 400GB SSD's
> > 256GB of RAM
> >
> > And multiple slave servers that looks like:
> > (1) E3-1290 CPU's
> > (2) Intel 520 SSD's
> > 32GB of RAM
> >
> > There's a significant difference between the master and slaves.
>
> Can you show us the explain analyze result on both master and slave?
>
> > Does the ANALYZE command run on each system, and work differently on each
> > system, or would the slave servers use the query plans from the master
> > machine?
>
> ANALYZE can only be executed on master. Slave creates its own
> plan. However since statistics should be same as master, I guess if
> you get different plan, then postgresql.conf maybe different among
> master and slave.
>
> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp
>