X-Original-To: pgsql-sql-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 5FA25329EB5 for ; Thu, 9 Sep 2004 06:33:50 +0100 (BST) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 77958-02 for ; Thu, 9 Sep 2004 05:33:40 +0000 (GMT) Received: from angel.lonelyplanet.com.au (mail.lonelyplanet.com.au [202.147.44.168]) by svr1.postgresql.org (Postfix) with ESMTP id 20E67329C70 for ; Thu, 9 Sep 2004 06:33:39 +0100 (BST) Received: from shiva.au.lpint.net ([192.168.61.22]) by angel with InterScan Messaging Security Suite; Thu, 09 Sep 2004 15:30:53 +1000 Received: by shiva.au.lpint.net with Internet Mail Service (5.5.2656.59) id ; Thu, 9 Sep 2004 15:30:57 +1000 Message-ID: <82E30406384FFB44AFD1012BAB230B55037D0584@shiva.au.lpint.net> From: Theo Galanakis To: pgsql-sql@postgresql.org Subject: Query Plan Date: Thu, 9 Sep 2004 15:30:48 +1000 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2656.59) Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C4962E.29F3C4C0" X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=2.0 tagged_above=0.0 required=5.0 tests=DNS_FROM_RFCI_DSN, EXCUSE_16, HTML_20_30, HTML_MESSAGE X-Spam-Level: ** X-Archive-Number: 200409/58 X-Sequence-Number: 18904 This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ------_=_NextPart_001_01C4962E.29F3C4C0 Content-Type: text/plain Have a question regarding when a Query Plan uses an Index. I have a basic statement This query uses the Index Scan: explain analyse select * from tablea where columna_id < 57 This query uses Seq Scan: explain analyse select * from tablea where columna_id < 58 There are about 5000 records in this table, and columna_id is the primary key, which is Indexed... And recently recreated. My question is why is the Plan not using the index on the second occasions? Theo ______________________________________________________________________ This email, including attachments, is intended only for the addressee and may be confidential, privileged and subject to copyright. If you have received this email in error, please advise the sender and delete it. If you are not the intended recipient of this email, you must not use, copy or disclose its content to anyone. You must not copy or communicate to others content that is confidential or subject to copyright, unless you have the consent of the content owner. ------_=_NextPart_001_01C4962E.29F3C4C0 Content-Type: text/html Content-Transfer-Encoding: quoted-printable Query Plan

Have a question regarding when a Query Pla= n uses an Index.

I have a basic statement

This query uses the Index Scan:
explain analyse select * from tablea wher= e columna_id < 57

This query uses Seq Scan:
explain analyse select * from tablea wher= e columna_id < 58

There are about 5000 records in this table= , and columna_id is the primary key, which is Indexed... And recently recre= ated.

My question is why is the Plan not using t= he index on the second occasions?

Theo

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This email, including= attachments, is intended only for the addressee
and may be confidential= , privileged and subject to copyright. If you
have received this email = in error, please advise the sender and delete
it. If you are not the in= tended recipient of this email, you must not
use, copy or disclose its c= ontent to anyone. You must not copy or
communicate to others content t= hat is confidential or subject to
copyright, unless you have the consen= t of the content owner.
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