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Re: PostgreSQL 8.4 performance tuning questions

From: tv(at)fuzzy(dot)cz
To: "Rauan Maemirov" <rauan(at)maemirov(dot)com>
Cc: tv(at)fuzzy(dot)cz, pgsql-performance(at)postgresql(dot)org
Subject: Re: PostgreSQL 8.4 performance tuning questions
Date: 2009-07-30 14:24:38
Message-ID: 21043.62.40.76.70.1248963878.squirrel@sq.gransy.com (view raw or flat)
Thread:
Lists: pgsql-performance
> Unfortunately had to downgrade back to 8.3. Now having troubles with
> that and still solving them.
>
> For future upgrade, what is the basic steps?

1. create database
2. dump the data from the old database
3. load the data into the new database
4. analyze etc. (I prefer to do this manually at the beginning)
5. check that everything is working (that the correct execution plans are
used, etc.)

You may even run the (2) and (3) at once - use pipe instead of a file.

>
>>Was the database analyzed recently?
> Hm... there was smth like auto analyzer in serverlog when i started it
> first time, but i didn't mention that.
> Should I analyze whole db? How to do it?

Just execute 'ANALYZE' and the whole database will be analyzed, but when
the autovacuum daemon is running this should be performed automatically (I
guess - check the pg_stat_user_tables, there's information about last
manual/automatic vacuuming and/or analysis).

> And how should I change _cost variables?

I haven't noticed you've not modified those variables, so don't change them.

> I/O was very high. at first memory usage grew up and then began to full
> swap.

OK, this seems to be the cause. What were the original values of the
config variables? If you've lowered the work_mem and you need to sort a
lot of data, this may be a problem. What amounts of data are you working
with? If the data were not analyzed recently, the execution plans will be
inefficient and this may be the result.

regards
Tomas


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