Re: [HACKERS] GEQO optimizer (was Re: Backend message type 0x44 arrived while idle)
От | Oleg Bartunov |
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Тема | Re: [HACKERS] GEQO optimizer (was Re: Backend message type 0x44 arrived while idle) |
Дата | |
Msg-id | Pine.GSO.3.96.SK.990517175549.15218G-100000@ra обсуждение исходный текст |
Ответ на | Re: [HACKERS] GEQO optimizer (was Re: Backend message type 0x44 arrived while idle) (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: [HACKERS] GEQO optimizer (was Re: Backend message type 0x44 arrived while idle)
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Список | pgsql-hackers |
On Mon, 17 May 1999, Tom Lane wrote: > Date: Mon, 17 May 1999 09:44:18 -0400 > From: Tom Lane <tgl@sss.pgh.pa.us> > To: Oleg Bartunov <oleg@sai.msu.su> > Cc: pgsql-hackers@postgreSQL.org > Subject: Re: [HACKERS] GEQO optimizer (was Re: Backend message type 0x44 arrived while idle) > > Oleg Bartunov <oleg@sai.msu.su> writes: > > I confirm big join with 11 tables doesn't eats all memory+swap on > > my Linux box as before and it runs *forever* :-). It took already > > 18 minutes of CPU (P200, 64Mb) ! Will wait. > > 18 minutes??? It takes barely over a minute on my aging 75MHz HP-PA > box. (Practically all of which is planning time, since there are only > 10 tuples to join... or are you doing this on a realistically sized > set of tables now?) > Oops, I found the problem. I modified my test script to add 'vacuum analyze' after creating test data and it works really fast ! Great ! Now I'm wondering why do I need vacuum analyze after creating test data and indices ? What's the state of discussion in hackers ? Regards, Oleg > > This query doesn't use (expicitly) GEQO > > > select t0.a,t1.a as t1,t2.a as t2,t3.a as t3,t4.a as t4,t5.a as t5,t6.a as t6,t7.a as t7,t8.a as t8,t9.a as t9,t10.aas t10 > > from t0 ,t1,t2,t3,t4,t5,t6,t7,t8,t9,t10 > > where t1.a_id = t0.a_t1_id and t2.a_id=t0.a_t2_id and t3.a_id=t0.a_t3_id and t4.a_id=t0.a_t4_id and t5.a_id=t0.a_t5_idand t6.a_id=t0.a_t6_id and t7.a_id=t0.a_t7_id and t8.a_id=t0.a_t8_id and t9.a_id=t0.a_t9_id and t10.a_id=t0.a_t10_id; > > No, but since there are 11 tables mentioned, it will be sent to the GEQO > optimizer anyway with the default GEQO threshold of 11... > > regards, tom lane > _____________________________________________________________ Oleg Bartunov, sci.researcher, hostmaster of AstroNet, Sternberg Astronomical Institute, Moscow University (Russia) Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/ phone: +007(095)939-16-83, +007(095)939-23-83
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