Re: Need help in setting optimal configuration for a huge

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От Tom Lane
Тема Re: Need help in setting optimal configuration for a huge
Дата
Msg-id 20903.1130087167@sss.pgh.pa.us
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Ответ на Re: Need help in setting optimal configuration for a huge  ("Craig A. James" <cjames@modgraph-usa.com>)
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"Craig A. James" <cjames@modgraph-usa.com> writes:
> MIN() and MAX() -- These are surprisingly slow, because they seem to do a full table scan EVEN ON AN INDEXED COLUMN!
Idon't understand why, but happily there is an effective substitute: 

>    select mycolumn from mytable order by mycolumn limit 1;  -- same as MIN()

>    select mycolumn from mytable order by mycolumn desc limit 1;  -- same as MAX()

BTW, Postgres does know to do that for itself as of 8.1.

            regards, tom lane

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