From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Satoshi Nagayasu <nagayasus(at)nttdata(dot)co(dot)jp> |
Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: stats_block_level |
Date: | 2007-07-27 04:30:55 |
Message-ID: | 7173.1185510655@sss.pgh.pa.us |
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Satoshi Nagayasu <nagayasus(at)nttdata(dot)co(dot)jp> writes:
> I think the stats stuff should be on by default even if it causes
> some performance penalty.
> Because when we have performance problems on the production system,
> it needs more performance penalty (about 5%~) to measure the stats
> by turning their params on.
> In real scenario, we always need the performance information,
> so we always need to turn. So I want the performance information
> can be taken by default.
I don't really agree with this argument. I've been reading
pgsql-performance for some years now, and I can't recall any incident
whatsoever in which we asked somebody for their stats_block_level
numbers. To be honest I think those numbers are just about useless.
However, in the current state of the system it seems to be nearly
free to collect them if we are collecting row-level stats, and since
that's happening by default as of 8.3, it's probably worth simplifying
the user-visible behavior by collecting both sets of stats if we collect
either.
regards, tom lane
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