From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jim C. Nasby <decibel@decibel.org>
Cc: Neil Conway <neilc@samurai.com>
Cc: Christopher Petrilli <petrilli@gmail.com>
Cc: Ying Lu <ying_lu@cs.concordia.ca>
Cc: pgsql-general@postgresql.org
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] "Hash index" vs. "b-tree index" (PostgreSQL
Date: Tue, 10 May 2005 11:49:50 -0400
Message-ID: <594.1115740190@sss.pgh.pa.us> (raw)
In-Reply-To: <20050510153927.GB31103@decibel.org>
References: <427F6853.90308@cs.concordia.ca>
<427F757A.8000407@samurai.com>
<59d991c405050908271b55e673@mail.gmail.com>
<427F8321.5030702@samurai.com>
<20050509163423.GH35026@decibel.org>
<427F9211.2090008@samurai.com>
<20050509165133.GJ35026@decibel.org>
<427FFCD3.1010803@samurai.com>
<4407.1115698257@sss.pgh.pa.us>
<20050510153927.GB31103@decibel.org>
"Jim C. Nasby" <decibel@decibel.org> writes:
> What's the challange to making it adaptive, comming up with an algorithm
> that gives you the optimal bucket size (which I would think there's
> research on...) or allowing the index to accommodate different bucket
> sizes existing in the index at once? (Presumably you don't want to
> re-write the entire index every time it looks like a different bucket
> size would help.)
Exactly. That's (a) expensive and (b) really hard to fit into the WAL
paradigm --- I think we could only handle it as a REINDEX. So if it
were adaptive at all I think we'd have to support multiple bucket sizes
existing simultaneously in the index, and I do not see a good way to do
that.
Allowing a bucket size to be specified at CREATE INDEX doesn't seem out
of line though. We'd have to think up a scheme for index-AM-specific
index parameters ...
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, decibel@decibel.org, neilc@samurai.com, petrilli@gmail.com, ying_lu@cs.concordia.ca, pgsql-general@postgresql.org
Subject: Re: [PERFORM] "Hash index" vs. "b-tree index" (PostgreSQL
In-Reply-To: <594.1115740190@sss.pgh.pa.us>
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