From: Mladen Gogala <mladen.gogala@vmsinfo.com>
To: Scott Marlowe <scott.marlowe@gmail.com>
Cc: Igor Neyman <ineyman@perceptron.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: David Wilson <david.t.wilson@gmail.com>
Cc: Kenneth Marshall <ktm@rice.edu>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Postgres 9.0 has a bias against indexes
Date: Thu, 27 Jan 2011 15:44:10 -0500
Message-ID: <4D41D91A.3010308@vmsinfo.com> (raw)
In-Reply-To: <AANLkTinZTugcnu+6QUnH2Dh2Lu-WGRjd_rnYyG4YSwH9@mail.gmail.com>
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<17268.1296146447@sss.pgh.pa.us>
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<F4C27E77F7A33E4CA98C19A9DC6722A2070C2531@EXCHANGE.corp.perceptron.com>
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On 1/27/2011 3:37 PM, Scott Marlowe wrote:
> On Thu, Jan 27, 2011 at 1:31 PM, Mladen Gogala
> <mladen.gogala@vmsinfo.com> wrote:
>> There is INDEX UNIQUE SCAN PK_EMP. Oracle will use an index.
> That's because Oracle has covering indexes.
>
I am not sure what you mean by "covering indexes" but I hope that for
the larger table I have in mind, indexes will be used. For a small
table like this, not using an index may actually be a better plan. I
cannot compare because my development PostgreSQL cluster is on a much
weaker machine than the development Oracle database.
I even looked into Wikipedia for the notion of "covering index" and it
is defined as an index which contains all the data requested in a query.
This is not the case, EMP is not an index-organized table. The only
index used was the primary key, also available in the PostgreSQL version
of the table.
--
Mladen Gogala
Sr. Oracle DBA
1500 Broadway
New York, NY 10036
(212) 329-5251
www.vmsinfo.com
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To: pgsql-performance@postgresql.org
Cc: mladen.gogala@vmsinfo.com, scott.marlowe@gmail.com, ineyman@perceptron.com, tgl@sss.pgh.pa.us, david.t.wilson@gmail.com, ktm@rice.edu
Subject: Re: Postgres 9.0 has a bias against indexes
In-Reply-To: <4D41D91A.3010308@vmsinfo.com>
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