Re: pgsql: Transforms for jsonb to PL/Perl

On Tue, 03 Apr 2018 17:37:04 -0400
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> I wrote:
> > Hm, it fails on my own machine too (RHEL6, perl 5.10.1), with the
> > same "cannot transform this Perl type to jsonb" symptoms. A bit
> > of tracing shows that SvTYPE(in) is returning SVt_PVIV in some
> > of the failing cases, and SVt_PVNV in others.
>
> I tried to fix this by reducing the amount of knowledge that function
> embeds about the possible SvTYPEs. After the special cases for AV,
> HV, and NULL, the attached just tests SvIOK, SvNOK, and SvPOK, and
> does the right thing for each case.
>
> This results in one change in the module's test results: the example
> that thinks it's returning a regexp match result no longer fails,
> but just returns the scalar result (0). I'm inclined to think that
> this is correct/desirable and the existing behavior is an accidental
> artifact of not coping with Perl's various augmented representations
> of scalar values.
>
> Thoughts?
>
> regards, tom lane
>

Hello.
I think that there is a mistake in test:
CREATE FUNCTION testRegexpToJsonb() RETURNS jsonb
LANGUAGE plperl
TRANSFORM FOR TYPE jsonb
AS $$
return ('1' =~ m(0\t2));
$$;

=~ is the operator testing a regular expression match.
Hence, testRegexpToJsonb function returns true/false values
(when used in scalar context, the return value
generally indicates the success of the operation).

I guess the right test will look a little bit different:
CREATE FUNCTION testRegexpToJsonb() RETURNS jsonb
LANGUAGE plperl
TRANSFORM FOR TYPE jsonb
AS $$
$a = qr//;
return ($a);
$$;

So, this may be the reason why the original testRegexpToJsonb returns
the scalar result.

--
Anthony Bykov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company