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Re: WIP: cross column correlation ...

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: WIP: cross column correlation ...
Date: 2011-02-26 06:57:54
Message-ID: 201102260657.p1Q6vtL01661@momjian.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Robert Haas wrote:
> > Actually, we *do* have some idea which tables are hot. ?Or at least, we
> > could. ? Currently, pg_stats for tables are "timeless"; they just
> > accumulate from the last reset, which has always been a problem in
> > general for monitoring. ?If we could make top-level table and index
> > stats time-based, even in some crude way, we would know which tables
> > were currently hot. ?That would also have the benefit of making server
> > performance analysis and autotuning easier.
> 
> I think there would be value in giving the DBA an easier way to see
> which tables are hot, but I am really leery about the idea of trying
> to feed that directly into the query planner.  I think this is one of
> those cases where we let people tune it manually for starters, and
> then wait for feedback.  Eventually someone will say "oh, I never tune
> that by hand any more, ever since I wrote this script which does the
> following computation... and I just run it out cron".  And then we
> will get out the party hats.  But we will never get the experience we
> need to say what that auto-tuning algorithm will be unless we first
> provide the knob for someone to fiddle with manually.

It is also possible we will implement a manual way and never get around
to automating it.   :-(

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +

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