From: | "Tyler Durden" <tylersticky(at)gmail(dot)com> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Seq Scan |
Date: | 2007-06-01 17:24:44 |
Message-ID: | ab07320e0706011024n4383117an1d69b96584536a71@mail.gmail.com |
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Thread: | |
Lists: | pgsql-general |
Ok, my bad.
But why this happens:
# explain ANALYZE select id from table_name where id>200000;
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------
Index Scan using table_name_pkey on table_name (cost=0.00..2618.96
rows=68960 width=4) (actual time=220.543..1479.495 rows=66730 loops=1)
Index Cond: (id > 200000)
Total runtime: 1504.839 ms
(3 rows)
dun=# explain ANALYZE select id from table_name where id>10;
QUERY PLAN
----------------------------------------------------------------------------------------------------------------------
Seq Scan on table_name (cost=0.00..9268.12 rows=266703 width=4)
(actual time=107.935..2733.592 rows=266720 loops=1)
Filter: (id > 10)
Total runtime: 2833.744 ms
(3 rows)
It uses Index Scan for id>200000 and Seq Scan for id>10?!
On 6/1/07, Joshua D. Drake <jd(at)commandprompt(dot)com> wrote:
> Nothing. You have to scan the table because you aren't giving postgresql
> anything to use the index by.
>
> Joshua D. Drake
>
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