Re: Full Text Index disk space requirements

From: Maarten Boekhold <Maarten(dot)Boekhold(at)reuters(dot)com>
To: typea(at)l-i-e(dot)com
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Full Text Index disk space requirements
Date: 2002-11-26 12:48:42
Message-ID: T5eccd06734c407b7066f0@reuters.com
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Hi,

if memory serves me right, the space requirements for this would be
something like:

42 (per tuple overhead)
4 (size of OID?)
16 (substitute with the maximum length of any 'string' in your
fulltext.sorted)
+ -------------
62
20,000,000 (substitute with number of lines in fulltext.sorted,
i.e. 'wc -l fulltext.sorted')
*---------------------------
1,240,000,000

or about 1.2G?

or
On 11/26/2002 01:36:59 PM typea wrote:
> Wouldn't using f1.string = 'perth' be faster than f1.string ~ '^perth'
and
> equally useful? Or is ~ with ^ somehow actually faster than the
seemingly
> simple = comparison?

f1.string = 'perth' would only match 'perth', while f1.string ~ '^perth'
would also match 'perthinent' (yes, I know this word does not exist).

Maarten

ps. are you trying to use the stuf from the 'fulltextindex' directory in
contrib/? I originally wrote this as an experiment, and it actually turned
out not to be fast enough for my purpose. I've never done anything with
full text indexing again, but I believe that currently there are better
solutions based on PostgreSQL (i.e. OpenFTI?)

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