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From: Postgres <postgres@maestro.srcc.lsu.edu>
To: postgres@postgres.Berkeley.EDU
Subject: Re:  Tuple-Functions on variable tables ?
Date: Mon, 17 Oct 94 18:37:28 CDT
Message-ID: <9410172337.AA02734@maestro.srcc.lsu.edu> (raw)

On 30 Sep 1994, Wolf-D. Ihlenfeldt writes

> But how to I formulate a query with
>    my_func(class1,class1)
>    
> or
>  
>    my_func(class3,class4)
>  
> where class3 and 4 may have a slightly different structure, but do
> contain the fields used in the function for the comparison.
> I have not found a way to pass classes which are different to
> those in the prototype htrough the parser. Is there some way
> to do this ?

You could do something like

 define function my_func (language = "c", returntype = bool,
   trusted="t", percall_cpu = "costly!!!")
   arg is (class1,class1) as "/path/myfunc.so"

where class1 is a bogus class with no data.  It simply has all the
attributes you want to test.  Then, when you create any real class
that you want to test, you just have it inherit class1.  This ought
to work because C functions will take any class that inherits the
one that it is defined to take.

If you want to get real adventurous, you can use parts of the source
code in your C function ( I recommend looking at the source for
GetAttributeByName() ) to pull in the data for attributes that are
not even inherited.

Sean Steiner
ssteiner@maestro.srcc.lsu.edu


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