Fix memory leaks in PL/Python.

Previously, plpython was in the habit of allocating a lot of stuff in
TopMemoryContext, and it was very slipshod about making sure that stuff
got cleaned up; in particular, use of TopMemoryContext as fn_mcxt for
function calls represents an unfixable leak, since we generally don't
know what the called function might have allocated in fn_mcxt.  This
results in session-lifespan leakage in certain usage scenarios, as for
example in a case reported by Ed Behn back in July.

To fix, get rid of all the retail allocations in TopMemoryContext.
All long-lived allocations are now made in sub-contexts that are
associated with specific objects (either pl/python procedures, or
Python-visible objects such as cursors and plans).  We can clean these
up when the associated object is deleted.

I went so far as to get rid of PLy_malloc completely.  There were a
couple of places where it could still have been used safely, but on
the whole it was just an invitation to bad coding.

Haribabu Kommi, based on a draft patch by Heikki Linnakangas;
some further work by me

1 files changed, 8 insertions, 11 deletions

diff --git a/src/pl/plpython/plpy_planobject.c b/src/pl/plpython/plpy_planobject.c
index 8305bd68e96..a9040efb502 100644
--- a/src/pl/plpython/plpy_planobject.c
+++ b/src/pl/plpython/plpy_planobject.c
@@ -11,6 +11,7 @@
 #include "plpy_planobject.h"
 
 #include "plpy_elog.h"
+#include "utils/memutils.h"
 
 
 static void PLy_plan_dealloc(PyObject *arg);
@@ -80,6 +81,7 @@ PLy_plan_new(void)
 	ob->types = NULL;
 	ob->values = NULL;
 	ob->args = NULL;
+	ob->mcxt = NULL;
 
 	return (PyObject *) ob;
 }
@@ -96,20 +98,15 @@ PLy_plan_dealloc(PyObject *arg)
 	PLyPlanObject *ob = (PLyPlanObject *) arg;
 
 	if (ob->plan)
+	{
 		SPI_freeplan(ob->plan);
-	if (ob->types)
-		PLy_free(ob->types);
-	if (ob->values)
-		PLy_free(ob->values);
-	if (ob->args)
+		ob->plan = NULL;
+	}
+	if (ob->mcxt)
 	{
-		int			i;
-
-		for (i = 0; i < ob->nargs; i++)
-			PLy_typeinfo_dealloc(&ob->args[i]);
-		PLy_free(ob->args);
+		MemoryContextDelete(ob->mcxt);
+		ob->mcxt = NULL;
 	}
-
 	arg->ob_type->tp_free(arg);
 }