Re: Disk wait problem... - Mailing list pgsql-general

From Ken Marshall
Subject Re: Disk wait problem...
Date
Msg-id ZTbS7H0czxr7rSlg@aart.rice.edu
Whole thread Raw
In response to Re: Disk wait problem...  (Adrian Klaver <adrian.klaver@aklaver.com>)
Responses Re: Disk wait problem...
List pgsql-general
> Hi,
> 
> I have a 1.6TB database with over 330 tables on a 4TB NVMe SSD. All
> tables are static (no updates); most in 8M and 33M row sizes. Queries have
> been great, until recently.

> Also attached is the relevant system journal entries for one query that
> took 2 seconds and two more that took 62 and 52 seconds... Unlike the
> above, these had 3 processes in disk-wait -- see attached screenshot...
> 
> I just stopped PG, updated the full backup which was done overnight (so
> the update took about a second), restarted PG and the problem persists...
> 
> Any suggestions where to look next?
> 
> Thanks,
> Pierre

Hi Pierre,

I have seen this type of behavior when parallel queries were enabled and
PostgreSQL decided that a parallel sequential scan query was the fastest
option. Try disabling them and see if that helps.

Regards,
Ken



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