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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Steven Flatt <steven.flatt@gmail.com>
Cc: Mark Kirkwood <markir@paradise.net.nz>
Cc: Gregory Stark <stark@enterprisedb.com>
Cc: Bill Moran <wmoran@collaborativefusion.com>
Cc: Vivek Khera <vivek@khera.org>
Cc: Pgsql performance <pgsql-performance@postgresql.org>
Subject: Re: When/if to Reindex
Date: Fri, 24 Aug 2007 12:15:25 -0400
Message-ID: <1759.1187972125@sss.pgh.pa.us> (raw)
In-Reply-To: <357fa7590708240722m204d678eid02b7ce3470eba1a@mail.gmail.com>
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	<20070808152757.9eb9bbcc.wmoran@collaborativefusion.com>
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	<357fa7590708090651p71b9bc47n66739f8dbbb4ff57@mail.gmail.com>
	<357fa7590708220955h441cd75ap4c0f0342a1c30a14@mail.gmail.com>
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	<17370.1187927942@sss.pgh.pa.us>
	<46CE6883.10104@paradise.net.nz>
	<357fa7590708240722m204d678eid02b7ce3470eba1a@mail.gmail.com>

"Steven Flatt" <steven.flatt@gmail.com> writes:
>> The fly in the ointment is that after collecting the pg_index definition
>> of the index, plancat.c also wants to know how big it is --- it calls
>> RelationGetNumberOfBlocks.

> Why do we even need to consider calling RelationGetNumberOfBlocks or looking
> at the pg_class.relpages entry?  My understanding of the expected behaviour
> is that while a reindex is happening, all queries run against the parent
> table are planned as though the index isn't there (i.e. it's unusable).

Where in the world did you get that idea?

If we had a REINDEX CONCURRENTLY it might work that way.  A normal
REINDEX cannot "mark" anything because it runs within a single
transaction; there is no way that it can emit any catalog changes
that will be visible before it's over.

			regards, tom lane



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