| From: | Rajmohan C <csrajmohan(at)gmail(dot)com> |
|---|---|
| To: | pgsql-hackers(at)postgresql(dot)org, pgsql-novice <pgsql-novice(at)postgresql(dot)org> |
| Subject: | Estimating selectivity of predicates involving string pattern matching |
| Date: | 2014-07-06 19:15:15 |
| Message-ID: | CAHaqV0hBdkne2sQQb5SGwwPHV4yEY71pJvye7gsOnR61GCRV1g@mail.gmail.com |
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| Lists: | pgsql-hackers pgsql-novice |
I recently upgraded my machine from PostgreSQL8.3 to PostgreSQL9.3.4. After
upgrade, when I ran TPC-H queries for performance testing, I could see
drastic change in timings. Especially TPC-H query 5 which was taking 4
minutes to execute in pgsql8.3, took just 15 seconds in postgresql9.3.4. I
think the reason it was taking 4 minutes in earlier version was because of
the error in selectivity of string pattern matching predicate in the query.
How was it fixed in recent version? Has any new algorithm been incorporated
to handle this?
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