From: | Andrew Sullivan <ajs(at)crankycanuck(dot)ca> |
---|---|
To: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: PostgreSQL ignores my indexes |
Date: | 2005-02-23 14:25:26 |
Message-ID: | 20050223142526.GA9072@phlogiston.dyndns.org |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-sql |
This is probably better on -performance, and is certainly a FAQ.
But. . .
On Wed, Feb 23, 2005 at 03:01:52PM +0100, Thomas Braad Toft wrote:
>
> Table device contains 5285 rows, tmeevent contains 834912 rows.
^^^^ ^^^^^^
> -> Seq Scan on tmeevent (cost=0.00..23606.12 rows=834912 width=138)
> (actual time=0.04..2193.97 rows=834912 loops=1)
^^^^^^
> -> Seq Scan on device (cost=0.00..564.85 rows=5285 width=29) (actual
> time=0.04..25.07 rows=5285 loops=1)
^^^^
> Why isn't the planner using my indexes? I tried making them as both rtree
Because there's no advantage to using an index when you are fetching
100% of both tables. This is the most efficient plan. Of course,
it's an open question whether you want to get 100% of both tables.
But that's what you're doing, and using the index would be more
expoensive than this.
A
--
Andrew Sullivan | ajs(at)crankycanuck(dot)ca
Information security isn't a technological problem. It's an economics
problem.
--Bruce Schneier
From | Date | Subject | |
---|---|---|---|
Next Message | KÖPFERL Robert | 2005-02-23 14:33:33 | dblink versus schemas. What to use in this case? |
Previous Message | Thomas Braad Toft | 2005-02-23 14:01:52 | PostgreSQL ignores my indexes |