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Re: Single Index Tuple Chain (SITC) method

From: Hannu Krosing <hannu(at)skype(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Martijn van Oosterhout <kleptog(at)svana(dot)org>,Bruce Momjian <bruce(at)momjian(dot)us>,PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>,Greg Stark <gsstark(at)mit(dot)edu>, PFC <lists(at)peufeu(dot)com>
Subject: Re: Single Index Tuple Chain (SITC) method
Date: 2006-06-29 16:59:26
Message-ID: 1151600366.5092.3.camel@localhost.localdomain (view raw or flat)
Thread:
Lists: pgsql-hackers
Ühel kenal päeval, N, 2006-06-29 kell 12:35, kirjutas Tom Lane:
> Martijn van Oosterhout <kleptog(at)svana(dot)org> writes:
> >> Tom - what do you think of the other related idea, that of reusing dead
> >> index entries ?
> 
> Possibly workable for btree now that we do page-at-a-time index scans;
> however I'm pretty hesitant to build any large infrastructure atop that
> change until we've got more performance results.  We might yet end up
> reverting it.
> 
> Another issue is that this would replace a simple hint-bit setting with
> an index change that requires a WAL entry.  There'll be more WAL traffic
> altogether from backends retail-deleting index tuples than there would
> be from VACUUM cleaning the whole page at once --- and it won't cut the
> I/O demand from VACUUM any, either, since VACUUM still has to scan the
> index.  AFAICS this wouldn't make VACUUM either cheaper or less
> necessary, so I'm not sure I see the point.

How can it generate more traffic ? 

When you replace a dead index entry with a live one, you just reuse
space - you would have to WAL log the index in both cases (adding a new
entry or replacing dead entry)

Espacially in the case, where you replace an index entryu with the same
value.

-- 
----------------
Hannu Krosing
Database Architect
Skype Technologies OÜ
Akadeemia tee 21 F, Tallinn, 12618, Estonia

Skype me:  callto:hkrosing
Get Skype for free:  http://www.skype.com



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Subject: Longer startup delay (was Re: Single Index Tuple Chain (SITC) method)
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