Re: Worse perfomance on 8.2.0 than on 7.4.14 - Mailing list pgsql-performance

From Dennis Bjorklund
Subject Re: Worse perfomance on 8.2.0 than on 7.4.14
Date
Msg-id 4597D6D0.8010902@zigo.dhs.org
Whole thread Raw
In response to Worse perfomance on 8.2.0 than on 7.4.14  (Rolf Østvik <rolfostvik@yahoo.no>)
Responses Re: Worse perfomance on 8.2.0 than on 7.4.14  (Rolf Østvik <rolfostvik@yahoo.no>)
List pgsql-performance
Rolf Østvik skrev:

> I have a simple query which uses 32ms on 7.4.14 and 1015ms on 8.2.0.
> I guess 7.4.14 creates a better execution plan than 8.2.0 for this query but


Try to turn off planner options in 8.2 to make it generate the same plan
as 7.4. Then run EXPLAIN ANALYZE on that query that generate the same
plan as in 7.4 and we can compare the costs and maybe understand what go
wrong.

For example, try

set enable_hashjoin to false;
set enable_bitmapscan to false;

but you might need to turn off more things to get it to generate the 7.4
plan.

/Dennis

pgsql-performance by date:

Previous
From: Dave Cramer
Date:
Subject: Re: Worse perfomance on 8.2.0 than on 7.4.14
Next
From: Tom Lane
Date:
Subject: Re: Worse perfomance on 8.2.0 than on 7.4.14