Re: cache estimates, cache access cost

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com>
Cc: Greg Smith <greg(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: cache estimates, cache access cost
Date: 2011-05-19 12:15:04
Message-ID: BANLkTi=v3CeRhJPzAz0StfVHgyGRYX9W3g@mail.gmail.com
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On Tue, May 17, 2011 at 6:11 PM, Cédric Villemain
<cedric(dot)villemain(dot)debian(at)gmail(dot)com> wrote:
> The point is to get ratio in cache, not the distribution of the data
> in cache (pgfincore also allows you to see this information).
> I don't see how a stable (a server in production) system can have its
> ratio moving up and down so fast without known pattern.

Really? It doesn't seem that hard to me. For example, your nightly
reports might use a different set of tables than are active during the
day....

> PS: there is very good blocker for the pg_class changes : what happens
> in a standby ? Maybe it just opens the door on how to unlock that or
> find another option to get the information per table but distinct per
> server. (or we don't care, at least for a first implementation, like
> for other parameters)

That's a good point, too.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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