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Re: Statistics issue

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Vlad Arkhipov <arhipov(at)dc(dot)baikal(dot)ru>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Statistics issue
Date: 2008-05-31 15:51:49
Message-ID: 16475.1212249109@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Vlad Arkhipov <arhipov(at)dc(dot)baikal(dot)ru> writes:
> EXPLAIN ANALYZE
> SELECT *
> FROM i
> WHERE d BETWEEN '2007-05-12' AND '2007-05-12'

> Index Scan using i_d on i  (cost=0.00..2.39 rows=1 width=402) (actual
> time=0.053..4.284 rows=1721 loops=1)
>   Index Cond: ((d >= '2007-05-12'::date) AND (d <= '2007-05-12'::date))
> Total runtime: 6.645 ms

> EXPLAIN ANALYZE
> SELECT *
> FROM i
> WHERE d = '2007-05-12'

> Index Scan using i_d on i  (cost=0.00..38.97 rows=1572 width=402)
> (actual time=0.044..4.250 rows=1721 loops=1)
>   Index Cond: (d = '2007-05-12'::date)
> Total runtime: 6.619 ms

Hmm, I wonder whether we shouldn't do something like this
http://archives.postgresql.org/pgsql-committers/2008-03/msg00128.php
for all range conditions, not just those made up by
prefix_selectivity().

			regards, tom lane

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