Re: == PostgreSQL Weekly News - February 21 2010 ==
От | David Fetter |
---|---|
Тема | Re: == PostgreSQL Weekly News - February 21 2010 == |
Дата | |
Msg-id | 20100222154007.GK2917@fetter.org обсуждение исходный текст |
Ответ на | == PostgreSQL Weekly News - February 21 2010 == (David Fetter <david@fetter.org>) |
Список | pgsql-announce |
On Sun, Feb 21, 2010 at 11:55:34PM -0800, David Fetter wrote: > == PostgreSQL 9.0 Feature of the Week == > > You can now control the behavior of distinct values per column using > ALTER TABLE...ALTER COLUMN...SET STATISTICS DISTINCT. Positive > numbers are assumed to be the number of distinct values, 0 tells the > planner to use the results from ANALYZE, and negative numbers (which > should be between -1 and 0, cause the planner to estimate the number > of distinct values as the estimated number of rows multiplied by the > absolute value of the number. This has changed since it was originally written. The syntax now is ALTER TABLE..ALTER COLUMN...SET (attribute=value, ...) For 9.0, attribute can be n_distinct or n_distinct_inherited, and this may expand in future major versions. Thanks to Robert Haas for pointing this out :) Cheers, David. -- David Fetter <david@fetter.org> http://fetter.org/ Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter Skype: davidfetter XMPP: david.fetter@gmail.com iCal: webcal://www.tripit.com/feed/ical/people/david74/tripit.ics Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate
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