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* local selectivity estimation - computing frequency of predicates
@ 2007-04-13 08:59 Avdhoot Kishore Saple <Avdhoot_Saple@infosys.com>
0 siblings, 1 reply; 2+ messages in thread
From: Avdhoot Kishore Saple @ 2007-04-13 08:59 UTC (permalink / raw)
To: pgsql-performance
Dear All.
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.)
Any suggestions regarding the same would be great
Thanks,
Avdhoot K. Saple
Junior Research Associate
High Performance & Grid Computing
Infosys Technologies Ltd., Bangalore
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* Re: local selectivity estimation - computing frequency of predicates
@ 2007-04-13 14:13 Tom Lane <tgl@sss.pgh.pa.us>
parent: Avdhoot Kishore Saple <Avdhoot_Saple@infosys.com>
0 siblings, 0 replies; 2+ messages in thread
From: Tom Lane @ 2007-04-13 14:13 UTC (permalink / raw)
To: Avdhoot Kishore Saple <Avdhoot_Saple@infosys.com>; +Cc: pgsql-performance
"Avdhoot Kishore Saple" <Avdhoot_Saple@infosys.com> 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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2007-04-13 08:59 local selectivity estimation - computing frequency of predicates Avdhoot Kishore Saple <Avdhoot_Saple@infosys.com>
2007-04-13 14:13 ` Tom Lane <tgl@sss.pgh.pa.us>
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