On Mon, 30 Aug 2010, Scott Marlowe wrote:
On Mon, Aug 30, 2010 at 12:20 AM, Gerhard Wiesinger <lists@xxxxxxxxxxxxx> 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?
What do you mean exactly? missing?
I did it not with psql but with a GUI program.
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?
I don't have a 8.3 version running anymore. But I'm havin an OLD version
of a nearly exactly query plan (The sort was missing due to performance
issues and it done now in a view, maybe also some more JOINS are added,
but all that doesn't have impacts on the basic principle of the query
plan):
http://www.wiesinger.com/tmp/pg_perf.txt
Tuning: Yes, on same machine with same parameters (manual diff on old
config and added manually the parameters again).
Thnx.
Ciao,
Gerhard
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http://www.wiesinger.com/
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