Re: local selectivity estimation - computing frequency of predicates

От: Tom Lane
Тема: Re: local selectivity estimation - computing frequency of predicates
Дата: ,
Msg-id: 18791.1176473594@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: local selectivity estimation - computing frequency of predicates  ("Avdhoot Kishore Saple")
Список: pgsql-performance

"Avdhoot Kishore Saple" <> writes:
> How to compute the frequency of predicate (e.g. Salary > $70000) in an
> SQL query from a DB's pre-defined indexes?". I'm specifically looking at
> how to retrieve information about indices (like number of pages at each
> level of index, range of attribute values etc.)

I don't think what you're looking for is exposed anywhere.  Postgres
doesn't rely on indexes for statistical information anyway; the
pg_statistic system catalog (see also pg_stats view) is used for that.

            regards, tom lane


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