2009/4/7 Tom Lane <tgl@sss.pgh.pa.us>:
> I wrote:
>> Bruce suggested what seemed like an excellent idea, which is to make
>> this self-documenting using the new default-arguments feature ---
>> it'll look something like this in \df:
>
>> List of functions
>> Schema | Name | Result data type | Argument data types
>> --------+------+------------------+----------------------------------------
>> public | foo | integer | label text, fast boolean DEFAULT false
>
> On poking into this, it's a bit uglier to do than I first thought.
> pg_proc.proargdefaults has to be the text representation of an
> expression tree. This means that to do it directly in pg_proc.h
> would take writing something like
>
> ({CONST :consttype 16 :consttypmod -1 :constlen 1 :constbyval true :constisnull false :location -1 :constvalue 1 [ 0
00 0 ]})
>
> Ugly as that is, it gets worse fast: the constvalue representation is
> machine-dependent, both as to width and endianness. And maintaining
> such things in the face of expression tree changes would be no fun
> either.
>
> So I think that's out. The only alternative that comes to mind is
> to have initdb issue an additional SQL command to establish the default
> after the bootstrap phase; that is, something like
>
> CREATE OR REPLACE FUNCTION
> pg_start_backup(label text, fast boolean DEFAULT false)
> RETURNS text LANGUAGE internal STRICT AS 'start_backup';
>
> in system_views.sql or some such place.
>
> Or we could just not bother with using a default here (ie, go back to
> declaring two pg_proc entries). It's not buying us all that much.
>
> Comments?
>
I like this idea - it should help for some spec types too
regards
Pavel
> regards, tom lane
>
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