Re: The mysterious pg_proc.protrftypes

po 25. 1. 2021 v 8:05 odesílatel Joel Jacobson <joel(at)compiler(dot)org> napsal:

> Hi,
>
> I'm trying to understand how pg_proc.protrftypes works.
>
> The documentation says "Data type OIDs for which to apply transforms.".
> For this column, there is no reference to any catalog table?
> I would guess it should be "(references pg_type.oid)", right?
>
> I tried to generate a value for this column to verify my hypothesis,
> but I struggle to find an example that produces a not null value here.
>
> I grepped the sources and found the "CREATE TRANSFORM FOR type_name"
> command,
> and found an extension using it named "bool_plperl" which I installed.
>
> I assumed this would cause a value, but no.
>
> Both of bool_plperl's two functions get null pg_proc.protrftypes values.
>
> I've tried running the full regression "make installcheck",
> but protrftypes doesn't seem to be covered:
>
> $ cd postgresql
> $ make installcheck
> ...
> =======================
> All 203 tests passed.
> =======================
> $ psql regression
> regression=# SELECT COUNT(*) FROM pg_proc WHERE protrftypes IS NOT NULL;
> count
> -------
> 0
> (1 row)
>
> Can someone please show me how to generate a function with a not null
> pg_proc.protrftypes value?
>

you should to use TRANSFORM clause in CREATE FUNCTION statement

https://www.postgresql.org/docs/current/sql-createfunction.html

CREATE EXTENSION hstore_plperl CASCADE;

CREATE FUNCTION test2() RETURNS hstore
LANGUAGE plperl
TRANSFORM FOR TYPE hstore
AS $$
$val = {a => 1, b => 'boo', c => undef};
return $val;
$$;

Regards

Pavel

> Many thanks.
>
> /Joel
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