From: Scott Marlowe <scott.marlowe@gmail.com>
To: luvar@plaintext.sk
Cc: pgsql-performance@postgresql.org
Subject: Re: Some question
Date: Tue, 6 Apr 2010 12:45:59 -0600
Message-ID: <p2kdcc563d11004061145g928107c0gc73c2b860eee677@mail.gmail.com> (raw)
In-Reply-To: <201003311746.38192.luvar@plaintext.sk>
References: <201003311746.38192.luvar@plaintext.sk>
2010/3/31 Ľubomír Varga <luvar@plaintext.sk>:
> Hi, stright to my "problem":
> 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)"
>
Looking at this it looks like you're using prepared queries, which
can't make as good of a decision as regular queries because the values
are opaque to the planner.
Can you provide us with the output of explain analyze of that query?
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To: pgsql-performance@postgresql.org
Cc: scott.marlowe@gmail.com, luvar@plaintext.sk
Subject: Re: Some question
In-Reply-To: <p2kdcc563d11004061145g928107c0gc73c2b860eee677@mail.gmail.com>
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