From: Tom Lane <tgl@sss.pgh.pa.us>
To: Josh Kupershmidt <schmiddy@gmail.com>
Cc: pgsql-docs <pgsql-docs@postgresql.org>
Subject: Re: docs update for count(*) and index-only scans
Date: Tue, 01 Nov 2011 18:51:02 -0400
Message-ID: <26833.1320187862@sss.pgh.pa.us> (raw)
In-Reply-To: <CAK3UJRGh3itWqYDPhogBav=334sEZcy2224eo1e4fwKc+cJhuQ@mail.gmail.com>
References: <CAK3UJRGh3itWqYDPhogBav=334sEZcy2224eo1e4fwKc+cJhuQ@mail.gmail.com>
Josh Kupershmidt <schmiddy@gmail.com> writes:
> func.sgml still claims that a sequential scan is the only way to
> execute a SELECT COUNT(*) query. I think this note should just be
> removed from the current docs, given the existence of index-only
> scans; patch attached.
Well, it might need adjustment, but I don't think we should remove it
outright. The people who complain that COUNT(*) is not O(1) are still
going to be complaining. On tables that are not read-mostly, there's
no reason to expect that index-only scans will even provide a material
speed boost, let alone be close to free.
regards, tom lane
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To: pgsql-docs@postgresql.org
Cc: tgl@sss.pgh.pa.us, schmiddy@gmail.com
Subject: Re: docs update for count(*) and index-only scans
In-Reply-To: <26833.1320187862@sss.pgh.pa.us>
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