Re: strange explain
От | Rod Taylor |
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Тема | Re: strange explain |
Дата | |
Msg-id | 04a601c1fa91$4bc4dfc0$0f02000a@jester обсуждение исходный текст |
Ответ на | strange explain (Oleg Bartunov <oleg@sai.msu.su>) |
Ответы |
Re: strange explain
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Список | pgsql-hackers |
It appears it scanes the type_idx once per opereator. IN gets broken down into ORs Is this what the TODO entry 'Make IN / NOT IN have similar performance as EXISTS' means? -- Rod ----- Original Message ----- From: "Oleg Bartunov" <oleg@sai.msu.su> To: "Pgsql Hackers" <pgsql-hackers@postgresql.org>; "Tom Lane" <tgl@sss.pgh.pa.us> Sent: Monday, May 13, 2002 9:42 AM Subject: [HACKERS] strange explain > Hi, > > > I've got performance problem and while I'dont ready to describe it > I'd like to ask about strange explain: > > tour=# explain analyze select * from tours where > ( operator_id in (2,3,4,5,7) and type_id = 2 ) or > ( operator_id = 8 and type_id=4 ); > > NOTICE: QUERY PLAN: > > Index Scan using type_idx, type_idx, type_idx, type_idx, type_idx, type_idx on tours (cost=0.00..12.25 rows=1 width=1091) (actual time=0.26..0.26 rows=0 loops=1) > Total runtime: 0.45 msec > > EXPLAIN > > What does many 'type_idx' means ? > > Theare are 2 indices - operator_idx and type_idx. > > > Regards, > Oleg > _____________________________________________________________ > 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 > > > ---------------------------(end of broadcast)--------------------------- > TIP 2: you can get off all lists at once with the unregister command > (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) >
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