Message-ID: <4407F031.6050706@obviously.com>
Date: Thu, 02 Mar 2006 23:28:49 -0800
From: Bryce Nesbitt <bryce1@obviously.com>
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To: pgsql-sql@postgresql.org
Subject: Sequential scan where Index scan expected (update)
References: <244004377.20060302124132@isb.com.pl>
	<2873.1141312882@sss.pgh.pa.us>
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I'm getting sequential scans (and poor performance), on scans using my
primary keys.  This is an older postgres.
Can anyone help figure out why?


demo=# \d xx_thing
                     Table "public.xx_thing"
         Column          |            Type             | Modifiers
-------------------------+-----------------------------+-----------
 thing_id              | bigint                      | not null
thing_model           | character varying(128)      |
 thing_color           | character varying(128)      |
 thing_year            | integer                     |
Indexes:
    "xx_thing_pkey" primary key, btree (thing_id)


demo=# analyze verbose xx_thing_event;
INFO:  analyzing "public.xx_thing_event"
INFO:  "xx_thing_event": 3374 pages, 3000 rows sampled, 197478 estimated
total rows


demo=# explain update xx_thing_event set thing_color='foo' where
thing_event_id=10000;
                             QUERY PLAN
---------------------------------------------------------------------
 Seq Scan on xx_thing_event  (cost=0.00..5842.48 rows=1 width=110)
   Filter: (thing_event_id = 10000)
(2 rows)


demo=# select * from version();
                                                 version
----------------------------------------------------------------------------------------------------------
 PostgreSQL 7.4.1 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.2.3
20030502 (Red Hat Linux 3.2.3-20)
(1 row)