From: Murphy Pope <pope_murphy@hotmail.com>
Subject: Re: ORDER BY and NULLs
Reply-To: pope_murphy@hotmail.com
Mail-Copies-To: pope_murphy@hotmail.com
References: <011d01c49e5b$c88fdb20$2766f30a@development.greatgulfhomes.com>
	<414DB1AB.5080207@sympatico.ca>
	<414DB594.5000300@numerixtechnology.de>
	<19733.1095613137@sss.pgh.pa.us>
	<414DBF6D.8040500@numerixtechnology.de>
	<87zn3mjeaw.fsf@stark.xeocode.com>
Lines: 30
User-Agent: KNode/0.7.7
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7Bit
Message-ID: <ot9gd.432$j15.304@fe25.usenetserver.com>
Date: Thu, 28 Oct 2004 12:52:31 -0400
To: pgsql-sql@postgresql.org

>> I just dug out the PostgreSQL book again because I thought I might've
>> garbled it:
>> 
>> Quote: "PostgreSQL will not index NULL values. Because an index will
>> never include NULL values, it cannot be used to satisfy the ORDER BY
>> clause of a query that returns all rows in a table."
> 
> You should just cross out that whole section. It's just flatly wrong.
> 
> I had always assumed it was just people bringing assumptions over from
> Oracle where it is true. Perhaps this book is to blame for some of the
> confusion. Which book is it?
> 
> Postgres indexes NULLs. It can use them for ORDER BY clauses.

Now I'm confused...  here's a quote from Bruce Momjian from Oct. 2003:

> To be specific, we do not do index NULL values in a column, but we
> easily index non-null values in the column.

And a comment from backend/access/gist/gist.c (appears a few times):

> GiST cannot index tuples with leading NULLs

So what's the story?  Do GiST indexes index NULLs? Do other index types
index NULLs? Is the comment wrong or am I misreading it?