From: Kevin Grittner <kgrittn@ymail.com>
To: Michael Kolomeitsev <mkolomeitsev@gmail.com>
To: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Pg makes nonoptimal choice between two multicolumn indexes with the same columns but in different order.
Date: Sat, 28 Dec 2013 13:03:28 -0800 (PST)
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Michael Kolomeitsev <mkolomeitsev@gmail.com> wrote:
> it is clear for me why t1_b_a_idx is better. The question is: Is
> postgresql able to see that?
For a number of reasons I never consider a bulk load complete until
I run VACUUM FREEZE ANALYZE on the table(s) involved. When I try
your test case without that, I get the bad index choice. When I
then run VACUUM FREEZE ANALYZE on the database I get the good index
choice.
There may be some lesser maintenance which sets up visibility
information and provides the planner with enough data to make a
good choice, I just noticed that you were not following what I
consider to be rote good practice, tried it, and it solved the
problem.
--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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To: pgsql-performance@postgresql.org
Cc: kgrittn@ymail.com, mkolomeitsev@gmail.com
Subject: Re: Pg makes nonoptimal choice between two multicolumn indexes with the same columns but in different order.
In-Reply-To: <1388264608.60549.YahooMailNeo@web122306.mail.ne1.yahoo.com>
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