GiST index performance

Revisiting the thread a month back or so, I'm still investigating
performance problems with GiST indexes in Postgres.

Looking at http://wiki.postgresql.org/wiki/PostgreSQL_8.4_Open_Items I'd
like to clarify the contrib/seg issue. Contrib/seg is vulnerable to
pathological behaviour which is fixed by my second patch, which can be
viewed as complete. Contrib/cube, being multi-dimensional, is not affected
to any significant degree, so should not need alteration.

A second quite distinct issue is the general performance of GiST indexes
which is also mentioned in the old thread linked from Open Items. For
that, we have a test case at
http://archives.postgresql.org/pgsql-performance/2009-04/msg00276.php for
btree_gist indexes. I have a similar example with the bioseg GiST index. I
have completely reimplemented the same algorithms in Java for algorithm
investigation and instrumentation purposes, and it runs about a hundred
times faster than in Postgres. I think this is a problem, and I'm willing
to do some investigation to try and solve it.

Do you have a recommendation for how to go about profiling Postgres, what
profiler to use, etc? I'm running on Debian Linux x86_64.

Matthew

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