From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Neil Conway <nconway(at)klamath(dot)dyndns(dot)org>, mloftis(at)wgops(dot)com, DCorbit(at)connx(dot)com, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: What is wrong with hashed index usage? |
Date: | 2002-06-21 16:51:53 |
Message-ID: | 200206211651.g5LGprw28745@candle.pha.pa.us |
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Lists: | pgsql-hackers |
Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > I remember three problems: build time, index size, and concurrency
> > problems. I was wondering about the equal key case myself, and assumed
> > hash may be a win there, but with the concurrency problems, is that even
> > possible?
>
> Sure. Many-equal-keys are a problem for btree whether you have any
> concurrency or not.
>
> > OK, I have reworded it. Is that better?
>
> It's better, but you've still discarded the original's explicit mention
> of concurrency problems. Why do you want to remove information?
OK, concurrency added. How is that?
>
> > How about an elog(NOTICE) for hash use?
>
> I don't think that's appropriate.
I was thinking of this during CREATE INDEX ... hash:
NOTICE: Hash index use is discouraged. See the CREATE INDEX
reference page for more information.
Does anyone else like/dislike that?
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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