| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Josh Berkus <josh(at)agliodbs(dot)com> |
| Cc: | Andrew Dunstan <andrew(at)dunslane(dot)net>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila(at)huawei(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Performance bug in prepared statement binding in 9.2? |
| Date: | 2013-09-11 21:12:53 |
| Message-ID: | 20130911211253.GF1138556@alap2.anarazel.de |
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| Thread: | |
| Lists: | pgsql-performance |
On 2013-09-11 11:35:45 -0700, Josh Berkus wrote:
> All,
>
> We've confirmed that this issue is caused by having long-running idle
> transactions on the server. When we disabled their queueing system
> (which prodiced hour-long idle txns), the progressive slowness went away.
>
> Why that should affect 9.X far more strongly than 8.4, I'm not sure
> about. Does that mean that 8.4 was unsafe, or that this is something
> which *could* be fixed in later versions?
The explanation is in
http://archives.postgresql.org/message-id/20130910132133.GJ1024477%40alap2.anarazel.de
The referenced commit introduced a planner feature. Funnily you seem to
have been the trigger for it's introduction ;)
> I'm also confused as to why this would affect BIND time rather than
> EXECUTE time.
Because we're doing the histogram checks during planning and not during
execution.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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