Re: Very large IN-clause is slow, but how to rewrite it?
| От | Joe Conway | 
|---|---|
| Тема | Re: Very large IN-clause is slow, but how to rewrite it? | 
| Дата | |
| Msg-id | 45E1D4FC.4050901@joeconway.com обсуждение исходный текст | 
| Ответ на | Re: Very large IN-clause is slow, but how to rewrite it? (Tom Lane <tgl@sss.pgh.pa.us>) | 
| Ответы | Re: Very large IN-clause is slow, but how to rewrite it? | 
| Список | pgsql-sql | 
Tom Lane wrote: > Richard Jones <rich@annexia.org> writes: >> I've been profiling a PG database / mix of applications and found that >> one statement which takes a very long time to execute is: > > PG 8.2 does better with long IN-lists ... although if the list is so > long as to be fetching a significant fraction of the table, you'll still > have problems. In that case I'd advise putting the values into a temp > table, ANALYZEing same, and doing "WHERE foo IN (SELECT x FROM tmp_table)". If 8.2, what about ... WHERE foo IN (select x from (values (1$),(2$),...,(N$)) as t(x)) ? It would be interesting to see how that compares performance-wise. Joe
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