Refactor PLy_spi_prepare to save two levels of indentation

Instead of checking whether the arglist is NULL and then if its length
is 0, do it in one step, and outside of the try/catch block.

Jan Urbański

src/pl/plpython/plpython.c

@@ -2817,6 +2817,7 @@ PLy_spi_prepare(PyObject *self, PyObject *args)
 	char	   *query;
 	void	   *tmpplan;
 	volatile MemoryContext oldcontext;
+	int			nargs;
 
 	if (!PyArg_ParseTuple(args, "s|O", &query, &list))
 	{
@@ -2835,21 +2836,17 @@ PLy_spi_prepare(PyObject *self, PyObject *args)
 	if ((plan = (PLyPlanObject *) PLy_plan_new()) == NULL)
 		return NULL;
 
+	nargs = list ? PySequence_Length(list) : 0;
+
+	plan->nargs = nargs;
+	plan->types = nargs ? PLy_malloc(sizeof(Oid) * nargs) : NULL;
+	plan->values = nargs ? PLy_malloc(sizeof(Datum) * nargs) : NULL;
+	plan->args = nargs ? PLy_malloc(sizeof(PLyTypeInfo) * nargs) : NULL;
+
 	oldcontext = CurrentMemoryContext;
 	PG_TRY();
 	{
-		if (list != NULL)
-		{
-			int			nargs,
-						i;
-
-			nargs = PySequence_Length(list);
-			if (nargs > 0)
-			{
-				plan->nargs = nargs;
-				plan->types = PLy_malloc(sizeof(Oid) * nargs);
-				plan->values = PLy_malloc(sizeof(Datum) * nargs);
-				plan->args = PLy_malloc(sizeof(PLyTypeInfo) * nargs);
+		int	i;
 
 		/*
 		 * the other loop might throw an exception, if PLyTypeInfo
@@ -2896,7 +2893,11 @@ PLy_spi_prepare(PyObject *self, PyObject *args)
 				elog(ERROR, "cache lookup failed for type %u", typeId);
 
 			Py_DECREF(optr);
-					optr = NULL;	/* this is important */
+			/*
+			 * set optr to NULL, so we won't try to unref it again in
+			 * case of an error
+			 */
+			optr = NULL;
 
 			plan->types[i] = typeId;
 			typeStruct = (Form_pg_type) GETSTRUCT(typeTup);
@@ -2908,8 +2909,6 @@ PLy_spi_prepare(PyObject *self, PyObject *args)
 						 errmsg("plpy.prepare does not support composite types")));
 			ReleaseSysCache(typeTup);
 		}
-			}
-		}
 
 		pg_verifymbstr(query, strlen(query), false);
 		plan->plan = SPI_prepare(query, plan->nargs, plan->types);
@@ -2943,6 +2942,7 @@ PLy_spi_prepare(PyObject *self, PyObject *args)
 	}
 	PG_END_TRY();
 
+	Assert(plan->plan != NULL);
 	return (PyObject *) plan;
 }