[cassandra] Fix batched query leak (#714)

* [cassandra] use query as resource for batched queries

* [cassandra] update batchstatement test

* [cassandra] remove query tag

Author: Kyle-Verhoog

ddtrace/contrib/cassandra/session.py

@@ -253,9 +253,7 @@ def _sanitize_query(span, query):
         # reset query if a string is available
         resource = getattr(query, "query_string", query)
     elif t == 'BatchStatement':
-        resource = 'BatchStatement'
-        q = "; ".join(q[1] for q in query._statements_and_parameters[:2])
-        span.set_tag("cassandra.query", q)
+        resource = '; '.join(q[1] for q in query._statements_and_parameters[:2])
         span.set_metric("cassandra.batch_size", len(query._statements_and_parameters))
     elif t == 'BoundStatement':
         ps = getattr(query, 'prepared_statement', None)

tests/contrib/cassandra/test.py

@@ -264,9 +264,15 @@ def test_batch_statement(self):
         spans = writer.pop()
         eq_(len(spans), 1)
         s = spans[0]
-        eq_(s.resource, 'BatchStatement')
+        eq_(
+            s.resource,
+            (
+                'INSERT INTO test.person_write (name, age, description) VALUES (\'Joe\', 1, \'a\'); '
+                'INSERT INTO test.person_write (name, age, description) VALUES (\'Jane\', 2, \'b\')'
+            )
+        )
         eq_(s.get_metric('cassandra.batch_size'), 2)
-        assert 'test.person' in s.get_tag('cassandra.query')
+        assert s.get_tag('cassandra.query') is None
 
 
 class TestCassPatchDefault(CassandraBase):