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From: Kevin Grittner <Kevin.Grittner@wicourts.gov>
To: Alexy Khrabrov <deliverable@gmail.com>
To: Greg Smith <gsmith@gregsmith.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: two memory-consuming postgres processes
Date: Fri, 02 May 2008 16:43:58 -0500
Message-ID: <481B44AF.EE98.0025.0@wicourts.gov> (raw)
In-Reply-To: <1F7A4C3D-C8A3-44BC-A324-E9BA409BB479@gmail.com>
References: <A728C858-76CF-473F-917B-3C9EA4AA75CF@gmail.com>
	<dcc563d10805021230i5916561k3962a41e2afa894c@mail.gmail.com>
	<27A4D379-2553-496D-A96C-102F2A5E62C2@gmail.com>
	<dcc563d10805021253n1589baa7u559fdfc8053d23d3@mail.gmail.com>
	<21403.1209759217@sss.pgh.pa.us>
	<72E02D29-848B-467A-AE6B-401568010254@gmail.com>
	<dcc563d10805021340u274ff4fegcf8902f66118d7c1@mail.gmail.com>
	<481B8160.2090106@emolecules.com>
	<C25E5DBA-B649-4483-B1A2-2A881522B891@gmail.com>
	<Pine.GSO.4.64.0805021714580.2455@westnet.com>
	<1F7A4C3D-C8A3-44BC-A324-E9BA409BB479@gmail.com>

>>> Alexy Khrabrov wrote: 
 
> SInce I don't index on that  
> new column, I'd assume my old indices would do -- do they change  
> because of rows deletions/insertions, with the effective new rows  
> addresses?
 
Every update is a delete and insert.  The new version of the row must
be added to the index.  Every access through the index then has to
look at both versions of the row to see which one is "current" for its
transaction.  Vacuum will make the space used by the dead rows
available for reuse, as well as removing the old index entries and
making that space available for new index entries.
 
-Kevin
 

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