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Re: docs update for count(*) and index-only scans

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Josh Kupershmidt <schmiddy(at)gmail(dot)com>, pgsql-docs <pgsql-docs(at)postgresql(dot)org>
Subject: Re: docs update for count(*) and index-only scans
Date: 2011-11-04 20:10:57
Message-ID: CA+TgmoatWSLoiTOJTXoR9SiB7EkBTHm1+MEo8z8axKS4fKQtjQ@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-docs
On Tue, Nov 1, 2011 at 8:07 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> It's the "lobotomized engines" that are the problem, IMO --- people
> coming from databases like mysql tend to think count(*) just means
> reading a table size counter that the engine has anyway.

This is probably a much less common misconception than formerly, due
to the rise of InnoDB and the falling-out-of-favor experienced by
MyISAM.

I think some pessimism removal is probably warranted.  Yeah, somebody
else might be faster than us on this test, but that's probably true of
many tests.  And on others we will be faster than them.

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

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Next:From: Scott MarloweDate: 2011-11-04 21:30:54
Subject: Re: docs update for count(*) and index-only scans
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Subject: Re: PGDATA confusion

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