From: T E Schmitz <mailreg@numerixtechnology.de>
To: Greg Stark <gsstark@mit.edu>
To: tgl@sss.pgh.pa.us
Cc: pgsql-sql@postgresql.org
Subject: Re: ORDER BY and NULLs
Date: Mon, 20 Sep 2004 09:04:26 +0100
Message-ID: <414E8F0A.6020602@numerixtechnology.de> (raw)
In-Reply-To: <874qltkbjc.fsf@stark.xeocode.com>
References: <011d01c49e5b$c88fdb20$2766f30a@development.greatgulfhomes.com>
<414DB1AB.5080207@sympatico.ca>
<414DB594.5000300@numerixtechnology.de>
<19733.1095613137@sss.pgh.pa.us>
<414DBF6D.8040500@numerixtechnology.de>
<87zn3mjeaw.fsf@stark.xeocode.com>
<414DEA7F.6050100@numerixtechnology.de>
<21812.1095625829@sss.pgh.pa.us>
<874qltkbjc.fsf@stark.xeocode.com>
Hello,
Greg Stark wrote:
> Tom Lane <tgl@sss.pgh.pa.us> writes:
>
>
>>>The paragraph continues:
>>>"If the SELECT command included the clause WHERE phone NOT NULL,
>>>PostgreSQL could use the index to satisfy the ORDER BY clause.
>>>An index that covers optional (NOT NULL) columns will not be used to
>>>speed table joins either."
>>
>>My goodness, it seems to be a veritable fount of misinformation :-(
>>
> I wonder if they just tried explain on a bunch of queries and noticed that
> postgres wasn't using an index for SELECT * FROM foo ORDER BY bar and came up
> with explanations for the patterns they saw?
This paragraph was in the chapter about PostgreSQL indexing and the
paragraph itself was entitled "Indexes and Null values".
--
Regards/Gruß,
Tarlika Elisabeth Schmitz
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To: pgsql-sql@postgresql.org
Cc: mailreg@numerixtechnology.de, gsstark@mit.edu, tgl@sss.pgh.pa.us
Subject: Re: ORDER BY and NULLs
In-Reply-To: <414E8F0A.6020602@numerixtechnology.de>
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