Re: tsearch2 dictionary that indexes substrings?

You want trigram based search.
ie.

postgresql -> 'pos', 'ost', 'stg', 'tgr', 'gre', 'res', 'esq', 'sql'

searching for 'gresq' is searching for 'gre' and 'res' and 'esq' which
is good friends with bitmap scan. Then a little LIKE '%gresq%' to filter
the results.

PS : indexing all substring means for long words you get huge number of
lexems...

On Fri, 20 Apr 2007 11:06:26 +0200, Tilmann Singer <tils-pgsql(at)tils(dot)net>
wrote:

> Hi,
>
> In this http://archive.netbsd.se/?ml=pgsql-hackers&a=2006-10&t=2475028
> thread Teodor Sigaev describes a way to make tsearch2 index substrings
> of words:
>
>> Brain storm method:
>>
>> Develop a dictionary which returns all substring for lexeme, for
>> example for word foobar it will be 'foobar fooba foob foo fo oobar
>> ooba oob oo obar oba ob bar ba ar'
>
> Did anyone do that already?
>
> If I understand it correctly such a dictionary would require to write
> a custom C component - is that correct? Or could I get away with
> writing a plpgsql function that does the above and hooking that
> somehow into the tsearch2 config?
>
>
> thanks, Til
>
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