From: | Josh Berkus <josh(at)agliodbs(dot)com> |
---|---|
To: | Shridhar Daithankar <shridhar_daithankar(at)myrealbox(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: More detail on settings for pgavd? |
Date: | 2003-11-20 18:00:34 |
Message-ID: | 200311201000.34694.josh@agliodbs.com |
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Lists: | pgsql-hackers pgsql-performance |
Shridhar,
> I would say -V 0.2-0.4 could be great as well. Fact to emphasize is that
> thresholds less than 1 should be used.
Yes, but not thresholds, scale factors of less than 1.0. Thresholds should
still be in the range of 100 to 1000.
> I will submit a patch that would account deletes in analyze threshold.
> Since you want to delay the analyze, I would calculate analyze count as
>
> n=updates + inserts *-* deletes
I'm not clear on how this is a benefit. Deletes affect the statistics, too.
> What does statistics gather BTW? Just number of rows or something else as
> well? I think I would put that on Hackers separately.
Number of tuples, degree of uniqueness, some sample values, and high/low
values. Just query your pg_statistics view for an example.
> I am still wary of inverting vacuum analyze frequency. You think it is
> better to set inverted default rather than documenting it?
See my post to Matthew.
--
Josh Berkus
Aglio Database Solutions
San Francisco
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