EXTRACT Clarification

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.

-tfo

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

> sszabo@bigpanda.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
> SQL
> defined it.