Summary: Correctly handle schema qualfied filter columns

This was assuming list_nth_cell returned a node pointer, but omitted
the required lfirst to turn the list cell into a pointer. Instead use
the convenience lsecond_node function.

Author: lfittl

src/pg_query_summary.c

@@ -537,7 +537,7 @@ pg_query_summary_walk_impl(Node *node, WalkState * state)
 				else if (num_fields == 3)
 				{
 					schema_name = linitial(ref->fields);
-					table_name = castNode(String, list_nth_cell(ref->fields, 1));
+					table_name = lsecond_node(String, ref->fields);
 				}
 
 				FilterColumn *fc = palloc(sizeof(FilterColumn));

test/summary_tests.c

@@ -1067,3 +1067,9 @@ void it_handles_all_tables_in_schema(TestState* test_state) {
 	Summary result = summary("GRANT SELECT ON ALL TABLES IN SCHEMA public TO myrole", 0, -1);
 	TEST_ASSERT_LIST_LENGTH(result.filter_columns, 0);
 }
+
+void it_handles_schema_qualified_columns(TestState* test_state) {
+	Summary result = summary("SELECT * FROM b.c WHERE a.b.c = 1", 0, -1);
+	TEST_ASSERT_LIST_LENGTH(result.filter_columns, 1);
+	TEST_SUMMARY_ASSERT_FILTER_COLUMN(result.filter_columns, "a", "b", "c");
+}

test/summary_tests_list.c

@@ -91,3 +91,4 @@
 &it_ignores_target_list_columns,
 &it_ignores_order_by_columns,
 &it_handles_all_tables_in_schema,
+&it_handles_schema_qualified_columns,