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EXTRACT Clarification

From: Thomas F(dot)O'Connell <tfo(at)sitening(dot)com>
To: Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com>
Cc: pgsql-docs(at)postgresql(dot)org
Subject: EXTRACT Clarification
Date: 2004-09-29 12:35:32
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Lists: pgsql-docspgsql-general
Switching this thread to DOCS and renaming it...

Anyway, I think that this situation calls for some clarification in the 
docs. If others agree, I'd be happy to submit a potential patch.

I'm thinking something like this (with thanks to Stephan):

Note: EXTRACT is not a true function. SQL defines it as an expression 
that happens to look similar to a function call.

Is this wording acceptable? I'd imagine putting it at the end of 9.8.1.

Also, are there other expressions that fall into this category? I don't 
know the spec well enough to know.


On Sep 29, 2004, at 1:30 AM, Stephan Szabo wrote:

> sszabo(at)bigpanda(dot)com
> On Tue, 28 Sep 2004, Thomas F.O'Connell wrote:
>>  From 11.5 in the docs:
>> "The syntax of the CREATE INDEX command normally requires writing
>> parentheses around index expressions, as shown in the second example.
>> The parentheses may be omitted when the expression is just a function
>> call, as in the first example."
>> But when I try this:
>> db=# CREATE INDEX expression_idx on some_table( extract( year from
>> some_column ) );
> Extract(year from some_column) is not really just a function call it's
> an expression that looks similar to a function call because that's how 
> defined it.

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