> 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?
The statistics is same on master and slave. Plans are made on master
and slave independently.
> 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?
If you have different postgresql.conf settings on slave, you could get
different plans on slave.
Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp
> On Sun, Nov 9, 2014 at 8:50 PM, Tatsuo Ishii <ishii@postgresql.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
>>
