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Re: Question on REINDEX

From: Bruno Wolff III <bruno(at)wolff(dot)to>
To: Bill Chandler <billybobc1210(at)yahoo(dot)com>
Cc: pgsql-perform <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Question on REINDEX
Date: 2005-04-18 19:53:58
Message-ID: 20050418195358.GA4961@wolff.to (view raw or flat)
Thread:
Lists: pgsql-performance
On Mon, Apr 18, 2005 at 12:21:42 -0700,
  Bill Chandler <billybobc1210(at)yahoo(dot)com> wrote:
> 
> Running PostgreSQL 7.4.2 on Solaris.
> 
> 1) When is it necessary to run REINDEX or drop/create
> an index?  All I could really find in the docs is:
> 
> "In some situations it is worthwhile to rebuild
> indexes periodically with the REINDEX command. (There
> is also contrib/reindexdb which can reindex an entire
> database.) However, PostgreSQL 7.4 has substantially
> reduced the need for this activity compared to earlier
> releases."

In pathologic cases it is possible to have a lot of empty space on a lot
of your index pages. Reindexing would change that to a smaller number.
In earlier versions, I think it was possible to have completely empty
pages and this happened for patterns of use (new values monotonically
increasing, oldest values deleted first) that were actually seen in
practice.

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