Обсуждение: Re: [HACKERS] Patch for user-defined C-language functions

> Postgresql operator with the following syntax
> 
> CREATE FUNCTION mytype3 ( mytype2 )
>        RETURNS mytype3
>        AS 'mytypes.so', 'mytype2_to_mytype3'
>        LANGUAGE 'C'
> 
> The syntax for the AS clause, which was 'AS <link-file>' becomes 
>     
>     AS <link_file>[, <link_name>]

Sounds great !

But I think the intuitive Syntax in SQL would use ():

CREATE FUNCTION mytype3 ( mytype2 )      RETURNS mytype3      AS 'mytypes.so(mytype2_to_mytype3)'      LANGUAGE 'C'

Syntax:AS <link_file>[(symbol_name)]

This is also how Illustra and now Informix does it.
(Instead of AS they say EXTERNAL NAME)

Andreas

Andreas Zeugswetter <andreas.zeugswetter@telecom.at> writes:
> But I think the intuitive Syntax in SQL would use ():
> CREATE FUNCTION mytype3 ( mytype2 )
>        RETURNS mytype3
>        AS 'mytypes.so(mytype2_to_mytype3)'
>        LANGUAGE 'C'
> Syntax:
>     AS <link_file>[(symbol_name)]

I think Bernard had the better solution --- the above presumes that
filenames won't ever have parens in them.  (Which, admittedly, is a
bad idea under most Unix shells --- but that doesn't mean we should
perpetuate the problem.)  Also, I'd rather see us keep the platform-
dependent ".so" extension at the end of its string, where it's easy
to spot and fix when needed.
        regards, tom lane

Andreas Zeugswetter wrote:
> 
> But I think the intuitive Syntax in SQL would use ():
> 
> CREATE FUNCTION mytype3 ( mytype2 )
>        RETURNS mytype3
>        AS 'mytypes.so(mytype2_to_mytype3)'
>        LANGUAGE 'C'
> 
> Syntax:
>         AS <link_file>[(symbol_name)]
> 
> This is also how Illustra and now Informix does it.
> (Instead of AS they say EXTERNAL NAME)
> 

The syntax  
AS <link_file>[(symbol_name)] 

would be easy to implement provided I could write your example as
CREATE FUNCTION mytype3 ( mytype2 )       RETURNS mytype3       AS 'mytypes.so'('mytype2_to_mytype3')       LANGUAGE
'C'

That way link_file and symbol_name both look like string tokens to 
the parser.  If it is implemented the way you write in the example with 
'mytypes.so(mytype2_to_mytype3)'

Then the parser sees the arguement of the AS clause as a single
string token which would have to be parsed separately.  Also, there is
some ambiguity in this form as to whether the string
'mytypes.so(mytype2_to_mytype3)'

is a single filename, or a filename and a link symbol

Bernie