Re: Index greater than 8k

From: Teodor Sigaev <teodor(at)sigaev(dot)ru>
To: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>
Cc: PgSQL General <pgsql-general(at)postgresql(dot)org>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Index greater than 8k
Date: 2006-10-31 07:55:00
Message-ID: 45470154.20405@sigaev.ru
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> The problem I am after is the 8k index size issue. It is very easy to
> get a GIST index (especially when using tsearch2) that is larger than that.
Hmm, tsearch2 GIST index is specially designed for support huge index entry:
first, every lexemes in tsvectore are transformed to hash value (with a help of
crc32), second, it's stripped all position infos, third, if size of array is
greater than TOAST_INDEX_TARGET then tsearch2 will make bit signature of
tsvector. Signature's length is fixed and equals to 252 bytes by default (+ 8
bytes for header of datum). All values on internal pages are represented as
signatures below.

So, tsearch2 guarantees that index entry will be small enough. If it's not true,
then there is a bug - pls, make test suite demonstrating the problem.

> Is recompiling the block size the option there?
> What are the downsides, except for the custom build?

Can you send exact error message?

--
Teodor Sigaev E-mail: teodor(at)sigaev(dot)ru
WWW: http://www.sigaev.ru/

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