Re: So, is COUNT(*) fast now?
| От | Robert Haas |
|---|---|
| Тема | Re: So, is COUNT(*) fast now? |
| Дата | |
| Msg-id | CA+TgmoaGKfu5kcZnQf_ZVjhy+micFdMhLiUaJZiXTHAVX2GTkw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: So, is COUNT(*) fast now? (Tom Lane <tgl@sss.pgh.pa.us>) |
| Ответы |
Re: So, is COUNT(*) fast now?
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| Список | pgsql-hackers |
On Fri, Oct 21, 2011 at 3:55 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote: > Robert Haas <robertmhaas@gmail.com> writes: >> Anyhow, here's the scoop. On my desktop machine running F14, running >> SELECT sum(1) FROM pgbench_accounts in a tight loop, 60 s worth of >> oprofile data: > >> 176830 13.0801 postgres postgres ExecProject > > Hm, that's weird. In both these cases, I'd have expected that > ExecProject would get optimized away thanks to selection of a physical > tlist for the scan node. Wonder if that got broken ... If it did, it looks like it wasn't recent. I set up the same test case on my MacBook using REL9_1_STABLE and REL9_0_STABLE and set a breakpoint on ExecProject(). Both back-branches appear to also call ExecProject() for every tuple. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
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