Re: Question about maintenance_work_mem and shared_buffer

[Rodrigo Barboza <rodrigombufrj@xxxxxxxxx>]

On Tue, May 21, 2013 at 1:03 PM, Amit Langote <amitlangote09@xxxxxxxxx> wrote:

On Wed, May 22, 2013 at 12:07 AM, Rodrigo Barboza
<rodrigombufrj@xxxxxxxxx> wrote:
> Hi, everyone.
> I have a doubt.
> I have a 32-bit postrgesql running with 2.5gb of shared_buffer.
> And I have maintenance_work_mem = 1gb and autovacuum_max_workers = 3.
> How maintenance_work_mem is related to shared_buffer?

They are independent settings.

> If the 3 workers uses 1gb, will the database crash?

Documentation does warn about not setting it (maintenance_work_mem) too high:

"Note that when autovacuum runs, up to autovacuum_max_workers times
this memory may be allocated, so be careful not to set the default
value too high."

http://www.postgresql.org/docs/9.3/static/runtime-config-resource.html

--
Amit Langote

So what would it be a reasonable value?

Because I saw some people suggesting to set it to total_mem / 8.

In my case I am running a 32 bit postgres with 64gb of total memory. My kernel is 64 bits (I know that is not ideal, but that's what I have now) to recognize and use the to total memory.