Re: which work memory parameter is used for what?

On Tue, Nov 8, 2016 at 1:53 PM, Hector Yuen <hector(at)infer(dot)com> wrote:

> Hello,
>
> I am confused on which are the parameters for different queries. I am
> trying to run VACUUM on a big table, and it is easier for me to set the
> work memory for the specific session instead of tuning it in
> postgresql.conf.
>
> I noticed that if I do:
>
> set work_mem='1GB';
>
> it doesn't help VACUUM, I have to do:
>
> set maintenance_work_mem='1GB';
>
> to accelerate the operation. I could notice that by running VACUUM VERBOSE
> and see that the table was scanned less times an the operation finished a
> lot faster.
>
> My question is, for which operations does work_mem matter and for which
> ones does maintenance_work_mem do? I am specially interested in operations
> like ANALYZE and VACUUM, I believe ANALYZE depends on work_mem and VACUUM
> on maintenance_work_mem.
>
> Can you confirm my understanding?
>
> Thanks
>
> --
> -h
>

*>I believe ANALYZE depends on work_mem and VACUUM on maintenance_work_mem.*
*No, ANALYZE is part of VACUUM. They both use maintenance_work_mem.*

*https://www.postgresql.org/docs/9.4/static/runtime-config-resource.html#RUNTIME-CONFIG-RESOURCE-MEMORY
<https://www.postgresql.org/docs/9.4/static/runtime-config-resource.html#RUNTIME-CONFIG-RESOURCE-MEMORY>*
--
*Melvin Davidson*
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.