| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Jung, Jinho" <jinho(dot)jung(at)gatech(dot)edu> |
| Cc: | "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Regarding query minimizer (simplifier) |
| Date: | 2018-10-13 21:59:06 |
| Message-ID: | 25899.1539467946@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
"Jung, Jinho" <jinho(dot)jung(at)gatech(dot)edu> writes:
> Hello, I am Jinho Jung, Phd Student from GeorgiaTech, and try to find any SQL queries that cause performance regression. While conducting evaluation, I found an interesting query which makes x80 times slower execution in version 10.5 than version 9.4. Please see the attached files, if you are interested.
Hm, testing this in the regression database, it seems pretty speedy
across all supported branches, and indeed slower in 9.4 than later
branches (~25 ms vs ~10 ms).
It seems likely that you're testing in a very different database,
perhaps one with many more tables ... but if you don't explain the
test scenario, we aren't going to have much luck investigating.
regards, tom lane
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