Re: analyzing intermediate query
От | Andrus |
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Тема | Re: analyzing intermediate query |
Дата | |
Msg-id | 72246E216337406EAD285F5A45533672@andrusnotebook обсуждение исходный текст |
Ответ на | Re: analyzing intermediate query (PFC <lists@peufeu.com>) |
Ответы |
Re: analyzing intermediate query
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Список | pgsql-performance |
> Oh, I just thought about something, I don't remember in which version it > was added, but : > > EXPLAIN ANALYZE SELECT sum(column1) FROM (VALUES ...a million > ntegers... ) AS v > > Postgres is perfectly happy with that ; it's either a bit slow (about 1 > second) or very fast depending on how you view things... I tried in 8.1.4 select * from (values (0)) xx but got ERROR: syntax error at or near ")" SQL state: 42601 Character: 26 Even if this works this may be not solution: I need to apply distinct to temporary table. Temporary table may contain duplicate values and without DISTINCT join produces invalid result. Temporary table itself is created from data from server tables, it is not generated from list. I can use SELECT dok.* FROM dok WHERE dokumnr IN (SELECT dokumnr FROM temptbl) but this seems never use bitmap index scan in 8.1.4 Sadly, creating second temporary table from first temporary table specially for this query seems to be only solution. When materialized row count will be added so that statistics is exact and select count(*) from tbl runs fast ? Andrus.
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