Re: Simplifying Text Search

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От Tom Lane
Тема Re: Simplifying Text Search
Дата
Msg-id 2345.1195139621@sss.pgh.pa.us
обсуждение исходный текст
Ответ на Re: Simplifying Text Search  (Peter Eisentraut <peter_e@gmx.net>)
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Peter Eisentraut <peter_e@gmx.net> writes:
> Am Mittwoch, 14. November 2007 schrieb Trevor Talbot:
>> But that coversion itself is fundamentally flawed, is the problem.

> I know it's incorrect, but with a different parser and/or dictionary you could 
> make it work.

No, I don't think so.  Trevor's killer point is that the token
boundaries chosen by the parser --- no matter *what* they are ---
might not line up with the substrings needed by a given LIKE pattern.
There isn't any mechanism in tsearch that will find the stored word
"foobar" if the search is for "foo" & "bar"; nor vice versa.

It might be possible to use a pg_trgm index in this way, since
AFAICT from the documents pg_trgm just chops up the substrings
blindly rather than trying to have smarts about word boundaries.

(And on third thought, I suppose you could emulate pg_tgrm with
a suitable parser and a lobotomized dictionary ... but it would
be pretty wasteful to use the tsearch mechanisms for that.)
        regards, tom lane


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