Re: immutable functions and enumerate type casts in indexes

Tom Lane ha scritto:
> Edoardo Panfili <edoardo(at)aspix(dot)it> writes:
>> my enumerated type is (this is a subset)
>> CREATE TYPE hibridation AS ENUM('none','genus','specie');
>
>> function declaration
>> CREATE FUNCTION ename(text,boolean,text,text RETURNS text AS
>> 'funzioniGDB.so' LANGUAGE C IMMUTABLE;
>
>> index creation (the type of ibrido is hibridation)
>> CREATE INDEX i_specie_nome_specie ON specie
>> (esterna_nome(ibrido::text,proParte,genere,specie));
>
>> the result is
>> ERROR: functions in index expression must be marked IMMUTABLE
>
> Now, maybe for your purposes here it's okay to consider it immutable.
> In that case what I'd suggest doing is redefining ename() to take the
> enum directly. You could invoke enum_out within the function if you
> really need a text equivalent.
thank you! this is the right way for me.
Now it works.

But i have a little question about parameters of enum_out.
Datum enum_out(PG_FUNCTION_ARGS);
this is a part of my function
-----------------------------------------------------------
Datum esterna_nome2(PG_FUNCTION_ARGS){
int label;
label = enum_out(fcinfo);
sprintf(debug,"false enum_out: \"%s\" ",unrolled);
elog(LOG, debug);
-----------------------------------------------------------
but it works only because my enum parameter is the first (and using
fcinfo is a little obscure).

I must build a FunctionCallInfo structure (I think) but how?

Edoardo