From: | Kjartan Ásþórsson <a98kjaas(at)student(dot)his(dot)se> |
---|---|
To: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Indexing and regular expressions |
Date: | 2002-04-07 10:09:36 |
Message-ID: | 103148120546.20020407120936@student.his.se |
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Lists: | pgsql-hackers |
Is there any indexing technique available I can use when joining tables
with a regular expression pattern in pgsql?
I know one method for indexing strings that will be matched with regular
expression patterns, and that is using so called k-gram indexes.
Indexing the string "kjartan" with k-gram index where k = 3 would
create "kja", "jar", "art", "rta", "tan" as an index. Ofcourse it is hard to
decide the size of k and I'm sure in many cases mulitple k values might
be needed, depending on the situation.
I have not done any major survey of available techniques, but I was
hoping I could get some pointers here.
I assume pgsql always uses nested loop join when joining relations which are
joined with regular expression pattern?
--
Kjartan Ásþórsson
http://www.kjarri.net
Tel: +46 (0)730 556705
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