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Re: bitmap AM design

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Neil Conway <neilc(at)samurai(dot)com>
Cc: Pailloncy Jean-Gerard <jg(at)rilk(dot)com>, Hannu Krosing <hannu(at)tm(dot)ee>,pgsql(at)mohawksoft(dot)com, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>,"Victor Y(dot) Yegorov" <viy(at)mits(dot)lv>
Subject: Re: bitmap AM design
Date: 2005-03-04 14:59:54
Message-ID: 27279.1109948394@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Neil Conway <neilc(at)samurai(dot)com> writes:
> (BTW, is poor concurrency really the biggest issue with hash indexes? If 
> so, there is some low-hanging fruit that I noticed a few years ago, but 
> never got around to fixing: _hash_doinsert() write-locks the hash 
> metapage on every insertion merely to increment a tuple counter. 

Given the short amount of time that lock is held, this wouldn't
win anything worth noticing.  Also, it's not "merely" to increment a
counter --- the counter drives decisions about whether to split buckets,
so any decrease in accuracy would lead directly to losses in overall
performance.

The lack of WAL support is a much bigger issue.

			regards, tom lane

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