Re: User Defined Types in Java

Martijn van Oosterhout wrote:
> The docs are your friend, see[1] in particular the input_function and
> the receive_function.
>
> [1] http://www.postgresql.org/docs/8.1/interactive/sql-createtype.html
>
>   
Ok, so there are two 'optional' arguments. Following my suggestion, the 
input and receive function would always take 3 arguments. Then, it's up 
to the function as such if it makes use of them or not. Do you see any 
problem with that? Is it bad from a performance perspective to always 
produce the values for the additional arguments? If so, an additional 
clause 'WITH EXTENDED PARAMETERS' (pending better suggestions :-) ) 
could be added to the CREATE TYPE.
>> I guess the pg_dump problem that you're thinking of is that there's no 
>> way to associate the functions with the type that they would belong to. 
>> Perhaps this could be done by adding a 'protype oid' column to the 
>> pg_proc table? Introducing that would probably help introducing SQL 2003 
>> semantics further on (I'm thinking of methods that belongs to types. Not 
>> very different from a function taking the type as it's first argument).
>>     
>
> I think the pg_dump is the fact that pg_dump needs to produce output
> that can be parsed to recreate the type and your suggestion only covers
> a very small set of possible type definitions (all in same lib,
> external func name = postgres func name, etc).
>
>   
That's very intentional. It will keep the functions of a type 
declaration in one place. I seriously doubt that there's an advantage to 
splitting functions for a single type between different libraries. I 
just can't see why or when that would be a good thing. Can you?

I also find it hard to come up with reasons why the PostgreSQL function 
name should be different from the name of the C function. I find no 
reasons at all that would motivate all the clutter equipped with the 
current construct.

> Hopefully something will be considered, but the first person who
> produces a patch will probably get priority :)
>
>   

I kind of guessed that would be the answer. I took a quick glance at the 
yacc grammar. Seems any of the suggestions would be possible to 
implement. So which is it?

CREATE TYPE complex;
CREATE TYPE complex AS SHELL;
DECLARE TYPE complex;

The first one has my vote.

Regards,
Thomas Hallgren