Re: add_path optimization

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Robert Haas" <robertmhaas(at)gmail(dot)com>
Cc: "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: add_path optimization
Date: 2009-02-03 14:47:50
Message-ID: 498804B6.EE98.0025.0@wicourts.gov
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>>> Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> FYI, I retested my queries on REL8_3_STABLE and the results were not
> all that different from CVS HEAD. So the problem is apparently
> specific to something your query is doing that mine isn't., rather
> than a general slowdown in planning (or else one of us goofed up the
> testing).

I know you said size doesn't matter, but just for the record, the ten
tables I loaded for this test put the database at 56G. I'm pulling
information together to share on this, but I was wondering: is there
any possibility that the tendency to use index scans in nested loops
(given the table sizes and the availability of useful indexes)
contributes to the difference?

Other possible factors:

Most keys are multi-column and include varchar-based data types.

Most columns are defined via domains.

(More info to follow.)

-Kevin

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