Free reference in correct Perl context. Backpatch to release 8.2. Patch from Tim Bunce.

src/pl/plperl/expected/plperl_plperlu.out

@@ -17,3 +17,49 @@ CONTEXT:  PL/Perl function "bar"
 SELECT * FROM foo(); -- used to cause backend crash (after switching to plperlu)
 ERROR:  syntax error at or near "invalid" at line 4. at line 2.
 CONTEXT:  PL/Perl function "foo"
+-- test redefinition of specific SP switching languages
+-- http://archives.postgresql.org/pgsql-bugs/2010-01/msg00116.php
+-- plperl first
+create or replace function foo(text) returns text language plperl  as 'shift';
+select foo('hey');
+ foo 
+-----
+ hey
+(1 row)
+
+create or replace function foo(text) returns text language plperlu as 'shift';
+select foo('hey');
+ foo 
+-----
+ hey
+(1 row)
+
+create or replace function foo(text) returns text language plperl  as 'shift';
+select foo('hey');
+ foo 
+-----
+ hey
+(1 row)
+
+-- plperlu first
+create or replace function bar(text) returns text language plperlu as 'shift';
+select bar('hey');
+ bar 
+-----
+ hey
+(1 row)
+
+create or replace function bar(text) returns text language plperl  as 'shift';
+select bar('hey');
+ bar 
+-----
+ hey
+(1 row)
+
+create or replace function bar(text) returns text language plperlu as 'shift';
+select bar('hey');
+ bar 
+-----
+ hey
+(1 row)
+

src/pl/plperl/plperl.c

 /**********************************************************************
  * plperl.c - perl as a procedural language for PostgreSQL
  *
- *	  $PostgreSQL: pgsql/src/pl/plperl/plperl.c,v 1.163 2010/01/30 01:46:57 adunstan Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plperl/plperl.c,v 1.164 2010/02/12 04:31:14 adunstan Exp $
  *
  **********************************************************************/
 
@@ -1762,8 +1762,11 @@ compile_plperl_function(Oid fn_oid, bool is_trigger)
 		{
 			hash_search(plperl_proc_hash, internal_proname,
 						HASH_REMOVE, NULL);
-			if (prodesc->reference)
+			if (prodesc->reference) {
+				select_perl_context(prodesc->lanpltrusted);
 				SvREFCNT_dec(prodesc->reference);
+				restore_context(oldcontext);
+			}
 			free(prodesc->proname);
 			free(prodesc);
 			prodesc = NULL;

src/pl/plperl/sql/plperl_plperlu.sql

@@ -16,3 +16,22 @@ $$ LANGUAGE plperlu; -- compile plperlu code
 SELECT * FROM bar(); -- throws exception normally (running plperl)
 SELECT * FROM foo(); -- used to cause backend crash (after switching to plperlu)
 
+-- test redefinition of specific SP switching languages
+-- http://archives.postgresql.org/pgsql-bugs/2010-01/msg00116.php
+
+-- plperl first
+create or replace function foo(text) returns text language plperl  as 'shift';
+select foo('hey');
+create or replace function foo(text) returns text language plperlu as 'shift';
+select foo('hey');
+create or replace function foo(text) returns text language plperl  as 'shift';
+select foo('hey');
+
+-- plperlu first
+create or replace function bar(text) returns text language plperlu as 'shift';
+select bar('hey');
+create or replace function bar(text) returns text language plperl  as 'shift';
+select bar('hey');
+create or replace function bar(text) returns text language plperlu as 'shift';
+select bar('hey');
+