From: Tom Lane <tgl@sss.pgh.pa.us>
To: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: jesper@krogh.cc
Cc: pgsql-performance@postgresql.org
Cc: oleg@sai.msu.su
Cc: teodor@sigaev.ru
Subject: Re: Queryplan within FTS/GIN index -search.
Date: Tue, 03 Nov 2009 10:35:44 -0500
Message-ID: <4730.1257262544@sss.pgh.pa.us> (raw)
In-Reply-To: <4AEFF056020000250002C195@gw.wicourts.gov>
References: <4AEF0369020000250002C183@gw.wicourts.gov>
<4AEF0369020000250002C183@gw.wicourts.gov>
<11587.1257207482@sss.pgh.pa.us>
<4AEFF056020000250002C195@gw.wicourts.gov>
"Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> Perhaps I'm missing something. My point was that there are words
> which are too common to be useful for index searches, yet uncommon
> enough to usefully limit the results. These words could typically
> benefit from tsearch2 style parsing and dictionaries; so declaring
> them as stop words would be bad from a functional perspective, yet
> searching an index for them would be bad from a performance
> perspective.
Right, but the original complaint in this thread was that a GIN index is
slow about searching for very common terms. The answer to that clearly
is to not index common terms, rather than worry about making the case
a bit faster.
It may well be that Jesper's identified a place where the GIN code could
be improved --- it seems like having the top-level search logic be more
aware of the AND/OR structure of queries would be useful. But the
particular example shown here doesn't make a very good case for that,
because it's hard to tell how much of a penalty would be taken in more
realistic examples.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, Kevin.Grittner@wicourts.gov, jesper@krogh.cc, oleg@sai.msu.su, teodor@sigaev.ru
Subject: Re: Queryplan within FTS/GIN index -search.
In-Reply-To: <4730.1257262544@sss.pgh.pa.us>
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