Re: WIP: hooking parser

2009/2/12 Peter Eisentraut <peter_e@gmx.net>:
> On Wednesday 11 February 2009 12:05:03 Pavel Stehule wrote:
>> It works. And I thing, this should to solve lot of special task
>> related to increase compatibility with Oracle, Informix, or it could
>> be usefull for some others (json support).
>>
>> postgres=# load 'decode';
>> LOAD
>> postgres=# select
>> decode(null::integer,2,'ahoj',3,'Petr',1,'Pavel',null, 'jaja');
>>  decode
>> --------
>>  jaja
>> (1 row)
>
> I think what you want here is some way to define a function that takes an
> arbitrary number of arguments of arbitrary type and let the function figure
> everything out.  I see no reason why this can't be a variant on CREATE
> FUNCTION, except that of course you need to figure out some API and function
> resolution details.  But it doesn't have to be a completely different concept
> like a binary plugin.
>

Actually I need add some metada to parameter list, Question is, what
is more simple and more readable - descriptive or procedural solution.
And what we are able to implement.

example DECODE(any1, any2, (asany1, asany2).,(asany2)+)

Actually I thing so with some hook of parser transform stage we should
to this task more simply.

I found next sample, that should be solved via hook - emulation of
Oracle behave '' is null.

Regards
Pavel