Re: Major performance problem after upgrade from 8.3 to 8.4

On Mon, Aug 30, 2010 at 12:20 AM, Gerhard Wiesinger <lists(at)wiesinger(dot)com> wrote:
> Hello,
>
> I just upgraded with pg_dump/restore from PostgreSQL 8.3.11 to 8.4.4 but I'm
> having major performance problems with a query with many left joins. Problem
> is that costs are now very, very, very high (was ok in 8.3). Analyze has
> been done. Indexes are of course there.
>
>  ->  Merge Left Join
> (cost=1750660.22..4273805884876845789194861338991916289697885665127154313046252183850255795798561612107149662486528.00
> rows=238233578115856634454073334945297075430094545596765511255148896328828230572227215727052643001958400
> width=16)
>        Merge Cond: (l.id = d2000903.fk_id)

Wow! Other than an incredibly high cost AND row estimate, was the
query plan the same on 8.3 or different?

> Details with execution plan can be found at:
> http://www.wiesinger.com/tmp/pg_perf_84.txt

What's up with the "(actual time=.. rows= loops=) " in the explain analyze?

> I know that the data model is key/value pairs but it worked well in 8.3. I
> need this flexibility.
>
> Any ideas?

Not really. I would like an explain analyze from both 8.3 and 8.4.
Are they tuned the same, things like work mem and default stats
target?