Re: One query run twice in parallel results in huge performance decrease - Mailing list pgsql-performance

From Scott Marlowe
Subject Re: One query run twice in parallel results in huge performance decrease
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Msg-id CAOR=d=3H5LZhVVx+2eC+DTTpCC8ksM5GCTaoA22eJ62eNwEqaA@mail.gmail.com
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In response to One query run twice in parallel results in huge performance decrease  (Jan Michel <Jan@mueschelsoft.de>)
List pgsql-performance
On Fri, Nov 29, 2013 at 3:07 PM, Jan Michel <Jan@mueschelsoft.de> wrote:
> Dear all,
> I have a quite strange problem running an extensive query on geo data
> checking for crossing ways. I don't know if this is a postgres or postgis
> problem, but I hope you can help. Running one thread is no problem, it
> finishes within 10-15 minutes. Run two of those queries in parallel and
> they will not finish within 24 hours. It is definitely not a caching or I/O
> problem.

What does your IO subsystem look like when you're running the query
both once and twice?

iostat, vmstat, iotop etc area ll useful here.


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