From: Ralph Mason <ralph.mason@telogis.com>
To: pgsql-performance@postgresql.org
Subject: Index Usage using IN
Date: Thu, 02 Feb 2006 09:12:59 +1300
Message-ID: <43E1164B.7020104@telogis.com> (raw)
Hi,
I have 2 tables both have an index on ID (both ID columns are an oid).
I want to find only only rows in one and not the other.
Select ID from TableA where ID not IN ( Select ID from Table B)
This always generates sequential scans.
Table A has about 250,000 rows. Table B has about 250,000 Rows.
We should get a Scan on Table B and a Index Lookup on Table A.
Is there any way to force this? enable_seqscan off doesn't help at all.
The Plan is
Seq Scan on tablea(cost=100000000.00..23883423070450.96 rows=119414 width=4)
Filter: (NOT (subplan))"
SubPlan ->
Seq Scan on tableb (cost=100000000.00..100004611.17 rows=242617
width=4)
Thanks
Ralph
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To: pgsql-performance@postgresql.org
Cc: ralph.mason@telogis.com
Subject: Re: Index Usage using IN
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