From: Andreas Pflug <Andreas.Pflug@web.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-performance@postgresql.org
Subject: Re: [SQL] Yet Another (Simple) Case of Index not used
Date: Sun, 20 Apr 2003 17:37:57 +0200
Message-ID: <3EA2BED5.9010707@web.de> (raw)
In-Reply-To: <27004.1050852329@sss.pgh.pa.us>
References: <EKEBJNAJDPKJBDFGJNIJAENMDBAA.denis@next2me.com>
<200304090918.45275.josh@agliodbs.com>
<20030419130146.GI1847@filer>
<21955.1050767928@sss.pgh.pa.us>
<20030420011336.GJ1847@filer>
<24735.1050809664@sss.pgh.pa.us>
<20030420062852.GK1847@filer>
<3EA27179.6010307@web.de>
<27004.1050852329@sss.pgh.pa.us>
Tom Lane wrote:
>It would be counting the wrong thing. auto-vacuum needs to know how
>many dead tuples are in a table, not how many live ones. Example:
>UPDATE doesn't change the live-tuple count (without this property,
>I don't think the sort of count maintenance Kevin is proposing could
>possibly be efficient enough to be interesting). But it does create
>a dead tuple that vacuum wants to know about.
>
>
>
I understand your point, but is this about VACUUM only or VACUUM ANALYZE
too? People wouldn't bother about big databases if it's still fast
(until the disk is full :-)
Do dead tuples affect query planning? I thought the plan only cares
about existing rows and their data patterns.
So count(*), pg_stat_all_tables.n_tup_ins, .n_tup_upd and .n_tup_del all
together can make a VACUUM ANALYZE necessary, right?
Regards,
Andreas
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To: pgsql-sql@postgresql.org
Cc: Andreas.Pflug@web.de, tgl@sss.pgh.pa.us, pgsql-performance@postgresql.org
Subject: Re: [SQL] Yet Another (Simple) Case of Index not used
In-Reply-To: <3EA2BED5.9010707@web.de>
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