Re: Non-linear Performance
От | Doug Fields |
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Тема | Re: Non-linear Performance |
Дата | |
Msg-id | 5.1.0.14.2.20020608203057.01f03068@pop.pexicom.com обсуждение исходный текст |
Ответ на | Re: Non-linear Performance (Neil Conway <nconway@klamath.dyndns.org>) |
Ответы |
Re: Non-linear Performance
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Список | pgsql-general |
>I can see the benefit when you're executing a small number of >enormously expensive queries (and those queries are CPU-bound); >but that situation is quite rare, IME. Bingo. I have some self-joins (Order N^2 at worst) on VARCHAR fields, which, if you have tables with millions of rows, take full CPU of 900 seconds or more sometimes - and I have a need to expand from 7-digit to 9-digit row counts - which could mean 10,000 times slower. I can speed that up from P3-1ghz to P4-2.4ghz, but not much. The best way to solve the above problem is to figure out a more efficient query, of course, or avoid the need for the query in the first place. Sometimes easier said than done. Also, the relatively slow speed for inserts with VARCHAR indices would conceivably be helped; I often insert data into a temp table and then INSERT INTO SELECT *... from the temp to the other one to get reasonable performance. I'd love to be able to turn off MVCC for those kinds of things; that is, instead of seeing one universal insert of 3 million rows, I wouldn't mind seeing them dribble in one at a time, thereby saving the overhead of MVCCing them. Cheers, Doug
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