[PATCH] PL/Perl (Mis-)Behavior with Runtime Error Reporting

Good day,

I just stumbled across this peculiarity in PL/Perl today writing a method
toinvoke Perl Regexes from a function: if a run-time error is raised in an
otherwise good function, the function will not run correctly again until
the connection to the database is reset. I poked around in the code and it
appears that it's because when elog() raises the ERROR, it doesn't first
take action to erase the system error message ($@) and consequently every
subsequent run has an error raised, even if it runs succesfully.

For example:

-- This comparison works fine.

template1=# SELECT perl_re_match('test', 'test');
perl_re_match
---------------
t
(1 row)

-- This one dies, for obvious reasons.

template1=# SELECT perl_re_match('test', 't{1}+?');
ERROR: plperl: error from function: (in cleanup) Nested quantifiers
before HERE mark in regex m/t{1}+ << HERE ?/ at (eval 2) line 4.

-- This should work fine again, but we still have this error raised...!

template1=# SELECT perl_re_match('test', 'test');
ERROR: plperl: error from function: (in cleanup) Nested quantifiers
before HERE mark in regex m/t{1}+ << HERE ?/ at (eval 2) line 4.

I don't know if the following is the best way to solve it, but I got
around it by modifying the error report in this part of PL/Perl to be a
NOTICE, cleared the $@ variable, and then raised the fatal ERROR. A simple
three line patch to plperl.c follows, and is attached.

plperl.c:
443c443,445
< elog(ERROR, "plperl: error from function: %s", SvPV(ERRSV, PL_na));
---
> elog(NOTICE, "plperl: error from function: %s", SvPV(ERRSV, PL_na));
> sv_setpv(perl_get_sv("@",FALSE),"");
> elog(ERROR, "plperl: error was fatal.");

Best Regards,
Jw.
--
John Worsley - lx(at)openvein(dot)com