Re[2]: [GENERAL] Joins and links
| От | Leon |
|---|---|
| Тема | Re[2]: [GENERAL] Joins and links |
| Дата | |
| Msg-id | 11879.990705@udmnet.ru обсуждение исходный текст |
| Ответ на | Re: [GENERAL] Joins and links (David Warnock <david@sundayta.co.uk>) |
| Список | pgsql-general |
Hello David, Monday, July 05, 1999 you wrote: D> I should say at this point that I never actually used the CLUSTER D> feature in MS SQL Server as we decided not to use that product after D> evaluating it. So I have no practical experience to know how much of the D> speed improvement wanted by Leon it would deliver. Not much. Because the main idea is to eliminate index scans entirely, whereas CLUSTER is merely "CLUSTER will help because once the index identifies the heap page for the first row that matches, all other rows that match are probably already on the same heap page, saving disk accesses and speeding up the query." - this is at best a few percent gain and means nothing if the database is entirely in memory (as it often is). Best regards, Leon
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