Message-ID: <488625E8.4070203@sigaev.ru>
Date: Tue, 22 Jul 2008 22:24:40 +0400
From: Teodor Sigaev <teodor@sigaev.ru>
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To: Tom Lane <tgl@sss.pgh.pa.us>
CC: Oleg Bartunov <oleg@sai.msu.su>,
	Pgsql Hackers <pgsql-hackers@postgresql.org>
Subject: Re: [PATCHES] GIN improvements
References: <483FD205.4090904@sigaev.ru> <486BC501.6060605@sigaev.ru>
	<27880.1215810535@sss.pgh.pa.us> <487A6E0C.3090600@sigaev.ru>
	<29437.1216742605@sss.pgh.pa.us> <48861758.4070507@sigaev.ru>
	<1636.1216749010@sss.pgh.pa.us>
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> Well, if that is required to be true then this whole design is pretty
> broken, because VACUUM doesn't hold any lock that would guarantee that
> no insert happens between the two calls.  If we fold the two AM calls
> into one call then it'd be okay for the index AM to take such a lock
> transiently during the single index-cleanup-plus-bulkdelete call.
Actually, lock doesn't needed. Just bulkdelete should not try to remove not yet 
"insertcleanuped" items pointer. That's easy because VacPageList is prepared 
before insertcleanup call.


> Maybe it'd be better if ambulkdelete *did* scan the pending list?

I don't like that idea because it requires to add a lot of code (concurrent 
deletion of pages in list), much simpler to call insertcleanup inside 
ginbulkdelete/ginvacuumcleanup.

> You'd still need at least page-level locking but perhaps not anything
> stronger.

That's close to trivial to revert this piece to add cleanup call to 
ginbulkdelete/ginvacuumcleanup. Early variants used this variant.
Reasons for new variant was:
  - defining needing of call of insertcleanup, and stats argument was used for
    it in both function. If it's a NULL then call cleanup.
  - I thought about statistic-based trigger for separate call of insertcleanup.
    Trigger should be fired on massive insert/update events very similar to
    trigger on massive delete for ambulkdelete. I'm very sorry but I didn't do it
    yet, and definitely I need some help here.

Do I revert that piece?

-- 
Teodor Sigaev                                   E-mail: teodor@sigaev.ru
                                                    WWW: http://www.sigaev.ru/