From: Andrus Moor <eetasoft@online.ee>
To: pgsql-sql@postgresql.org
Subject: Query runs very slowly in Postgres, but very fast in other DBMS
Date: Tue, 12 Apr 2005 00:43:10 +0300
Message-ID: <d3er3k$2m2d$1@news.hub.org> (raw)
Tables:
CREATE TABLE dok ( dokumnr NUMERIC(12),
CONSTRAINT dok_pkey PRIMARY KEY (dokumnr) );
CREATE TABLE rid ( dokumnr NUMERIC(12) );
CREATE INDEX rid_dokumnr_idx ON rid (dokumnr);
Query:
SELECT dokumnr FROM rid WHERE dokumnr NOT IN
(select dokumnr FROM dok);
runs VERY slowly in Postgres. It uses the following query plan:
Seq Scan on rid (cost=0.00..28698461.07 rows=32201 width=14)
Filter: (NOT (subplan))
SubPlan
-> Seq Scan on dok (cost=0.00..864.29 rows=10729 width=14)
In Microsoft Visual FoxPro this query runs fast. FoxPro uses indexes speed
up the query by comparing bitmaps.
Is it possible to speed up this query is Postgres ? How to force Postgres to
use indexes for this query ?
Andrus
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To: pgsql-sql@postgresql.org
Cc: eetasoft@online.ee
Subject: Re: Query runs very slowly in Postgres, but very fast in other DBMS
In-Reply-To: <d3er3k$2m2d$1@news.hub.org>
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