From: Timur Irmatov <thor@sarkor.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: index usage
Date: Fri, 17 Jan 2003 20:08:14 +0500
Message-ID: <87109443711.20030117200814@sarkor.com> (raw)
In-Reply-To: <11751.1042815424@sss.pgh.pa.us>
References: <10597430257.20030117164800@sarkor.com>
<11751.1042815424@sss.pgh.pa.us>
TL> Timur Irmatov <thor@sarkor.com> writes:
>> Limit (cost=0.00..0.19 rows=1 width=6) (actual time=0.43..0.43 rows=0 loops=1)
>> -> Index Scan using timeindex on mediumstats (cost=0.00..2898.96 rows=15185 width=6) (actual time=0.42..0.42 rows=0 loops=1)
TL> The planner has absolutely no clue about the behavior of your function,
TL> and so its estimate of the number of rows matched is way off, leading to
TL> a poor estimate of the cost of an indexscan. There is not much to be
TL> done about this in the current system (though I've speculated about the
TL> possibility of computing statistics for functional indexes).
you're absolutely right.
thanks.
TL> Just out of curiosity, why don't you lose all this year/month/day stuff
TL> and use a timestamp column? Less space, more functionality.
:-)
Well, I've a seen a lot of people on pgsql-general mailing list with
problems with dates, timestamps, and I was just scared of using
PostreSQL date and time types and functions..
May be, I should just try it myself before doing it other way...
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To: pgsql-performance@postgresql.org
Cc: thor@sarkor.com, tgl@sss.pgh.pa.us
Subject: Re: index usage
In-Reply-To: <87109443711.20030117200814@sarkor.com>
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