From: Ľubomír Varga <luvar@plaintext.sk>
To: pgsql-performance@postgresql.org
Subject: Some question
Date: Wed, 31 Mar 2010 17:46:38 +0200
Message-ID: <201003311746.38192.luvar@plaintext.sk> (raw)
Hi, stright to my "problem":
explain
SELECT * FROM t_route
WHERE t_route.route_type_fk = 1
limit 4;
"Limit (cost=0.00..0.88 rows=4 width=2640)"
" -> Seq Scan on t_route (cost=0.00..118115.25 rows=538301 width=2640)"
" Filter: (route_type_fk = 1)"
If I try to select constant 1 from table with two rows, it will be something
like this:
explain
SELECT * FROM t_route
WHERE t_route.route_type_fk = (SELECT id FROM t_route_type WHERE type = 2)
limit 4;
"Limit (cost=1.02..1.91 rows=4 width=2640)"
" InitPlan"
" -> Seq Scan on t_route_type (cost=0.00..1.02 rows=1 width=8)"
" Filter: ("type" = 2)"
" -> Seq Scan on t_route (cost=0.00..118115.25 rows=535090 width=2640)"
" Filter: (route_type_fk = $0)"
First query is done in about milicesonds. Second is longer than 60 seconds.
t_route is bigger table (~10M rows).
I think that it seq scans whole table. Is it bug? If no, how can I achieve
that second select will not take time to end of world...
Have a nice day and thanks for any reply.
--
Odborník na všetko je zlý odborník. Ja sa snažím byť výnimkou potvrdzujúcou
pravidlo.
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To: pgsql-performance@postgresql.org
Cc: luvar@plaintext.sk
Subject: Re: Some question
In-Reply-To: <201003311746.38192.luvar@plaintext.sk>
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