From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Geoghegan <pg@heroku.com>
cc: =?UTF-8?B?5aSn5aGa5oay5Y+4?= <otsuka.kenji@nttcom.co.jp>,
        pgsql-docs@postgresql.org, Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] The number of bytes is stored in index_size of
 pgstatindex() ?
In-reply-to: 
 <CAM3SWZQtQ2WDGRqa2g_dbfHuu9CebfWvJ_XpXggFoFG1mUYzXw@mail.gmail.com>
References: <56C5B2C7.7010604@nttcom.co.jp> <31925.1455817248@sss.pgh.pa.us>
 <CAM3SWZQtQ2WDGRqa2g_dbfHuu9CebfWvJ_XpXggFoFG1mUYzXw@mail.gmail.com>
Comments: In-reply-to Peter Geoghegan <pg@heroku.com>
	message dated "Thu, 18 Feb 2016 09:50:20 -0800"
Date: Thu, 18 Feb 2016 13:01:10 -0500
Message-ID: <377.1455818470@sss.pgh.pa.us>
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Sender: pgsql-docs-owner@postgresql.org

Peter Geoghegan <pg@heroku.com> writes:
> On Thu, Feb 18, 2016 at 9:40 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I think this is a bug and we ought to fix the code to include the
>> metapage in the reported index_size.  Thoughts?

> I tend to agree, but I think you should note that specifically in the
> documentation. I'm in favor of tools like pgstattuple and pageinspect
> going into this kind of detail in their documentation generally.

Yeah ... the numbers already appear not to add up because the root page
is counted in index_size but not any other column, so there's already
something worthy of explanation there.  Maybe something like "The reported
index_size will normally correspond to two more pages than are accounted
for by internal_pages + leaf_pages + empty_pages + deleted_pages, because
it also includes the index's metapage and root page".

			regards, tom lane


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