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))
 	{
@@ -2835,80 +2836,78 @@ 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	i;
+
+		/*
+		 * the other loop might throw an exception, if PLyTypeInfo
+		 * member isn't properly initialized the Py_DECREF(plan) will
+		 * go boom
+		 */
+		for (i = 0; i < nargs; i++)
 		{
-			int			nargs,
-						i;
+			PLy_typeinfo_init(&plan->args[i]);
+			plan->values[i] = PointerGetDatum(NULL);
+		}
 
-			nargs = PySequence_Length(list);
-			if (nargs > 0)
+		for (i = 0; i < nargs; i++)
+		{
+			char	   *sptr;
+			HeapTuple	typeTup;
+			Oid			typeId;
+			int32		typmod;
+			Form_pg_type typeStruct;
+
+			optr = PySequence_GetItem(list, i);
+			if (PyString_Check(optr))
+				sptr = PyString_AsString(optr);
+			else if (PyUnicode_Check(optr))
+				sptr = PLyUnicode_AsString(optr);
+			else
 			{
-				plan->nargs = nargs;
-				plan->types = PLy_malloc(sizeof(Oid) * nargs);
-				plan->values = PLy_malloc(sizeof(Datum) * nargs);
-				plan->args = PLy_malloc(sizeof(PLyTypeInfo) * nargs);
+				ereport(ERROR,
+						(errmsg("plpy.prepare: type name at ordinal position %d is not a string", i)));
+				sptr = NULL;	/* keep compiler quiet */
+			}
 
-				/*
-				 * the other loop might throw an exception, if PLyTypeInfo
-				 * member isn't properly initialized the Py_DECREF(plan) will
-				 * go boom
-				 */
-				for (i = 0; i < nargs; i++)
-				{
-					PLy_typeinfo_init(&plan->args[i]);
-					plan->values[i] = PointerGetDatum(NULL);
-				}
+			/********************************************************
+			 * Resolve argument type names and then look them up by
+			 * oid in the system cache, and remember the required
+			 *information for input conversion.
+			 ********************************************************/
 
-				for (i = 0; i < nargs; i++)
-				{
-					char	   *sptr;
-					HeapTuple	typeTup;
-					Oid			typeId;
-					int32		typmod;
-					Form_pg_type typeStruct;
-
-					optr = PySequence_GetItem(list, i);
-					if (PyString_Check(optr))
-						sptr = PyString_AsString(optr);
-					else if (PyUnicode_Check(optr))
-						sptr = PLyUnicode_AsString(optr);
-					else
-					{
-						ereport(ERROR,
-								(errmsg("plpy.prepare: type name at ordinal position %d is not a string", i)));
-						sptr = NULL;	/* keep compiler quiet */
-					}
-
-					/********************************************************
-					 * Resolve argument type names and then look them up by
-					 * oid in the system cache, and remember the required
-					 *information for input conversion.
-					 ********************************************************/
-
-					parseTypeString(sptr, &typeId, &typmod);
-
-					typeTup = SearchSysCache1(TYPEOID,
-											  ObjectIdGetDatum(typeId));
-					if (!HeapTupleIsValid(typeTup))
-						elog(ERROR, "cache lookup failed for type %u", typeId);
-
-					Py_DECREF(optr);
-					optr = NULL;	/* this is important */
-
-					plan->types[i] = typeId;
-					typeStruct = (Form_pg_type) GETSTRUCT(typeTup);
-					if (typeStruct->typtype != TYPTYPE_COMPOSITE)
-						PLy_output_datum_func(&plan->args[i], typeTup);
-					else
-						ereport(ERROR,
-								(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-								 errmsg("plpy.prepare does not support composite types")));
-					ReleaseSysCache(typeTup);
-				}
-			}
+			parseTypeString(sptr, &typeId, &typmod);
+
+			typeTup = SearchSysCache1(TYPEOID,
+									  ObjectIdGetDatum(typeId));
+			if (!HeapTupleIsValid(typeTup))
+				elog(ERROR, "cache lookup failed for type %u", typeId);
+
+			Py_DECREF(optr);
+			/*
+			 * 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);
+			if (typeStruct->typtype != TYPTYPE_COMPOSITE)
+				PLy_output_datum_func(&plan->args[i], typeTup);
+			else
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("plpy.prepare does not support composite types")));
+			ReleaseSysCache(typeTup);
 		}
 
 		pg_verifymbstr(query, strlen(query), false);
@@ -2943,6 +2942,7 @@ PLy_spi_prepare(PyObject *self, PyObject *args)
 	}
 	PG_END_TRY();
 
+	Assert(plan->plan != NULL);
 	return (PyObject *) plan;
 }