Add default consistency level per-Session

Fixes PYTHON-14

CHANGELOG.rst

@@ -1,7 +1,11 @@
-1.1.3
+1.2.0
 =====
 In Progress
 
+Features
+--------
+* Add Session.default_consistency_level (PYTHON-14)
+
 Bug Fixes
 ---------
 * Don't strip trailing underscores from column names when using the

cassandra/cluster.py

@@ -951,6 +951,15 @@ class Session(object):
     timeout, neither the registered callback or errback will be called.
     """
 
+    default_consistency_level = ConsistencyLevel.ONE
+    """
+    The default :class:`~ConsistencyLevel` for operations executed through
+    this session.  This default may be overridden by setting the
+    :attr:`~.Statement.consistency_level` on individual statements.
+
+    .. versionadded:: 1.2.0
+    """
+
     max_trace_wait = 2.0
     """
     The maximum amount of time (in seconds) the driver will wait for trace
@@ -1082,17 +1091,18 @@ class Session(object):
         elif isinstance(query, PreparedStatement):
             query = query.bind(parameters)
 
+        cl = query.consistency_level if query.consistency_level is not None else self.default_consistency_level
         if isinstance(query, BoundStatement):
             message = ExecuteMessage(
                 query_id=query.prepared_statement.query_id,
                 query_params=query.values,
-                consistency_level=query.consistency_level)
+                consistency_level=cl)
             prepared_statement = query.prepared_statement
         else:
             query_string = query.query_string
             if parameters:
                 query_string = bind_params(query.query_string, parameters)
-            message = QueryMessage(query=query_string, consistency_level=query.consistency_level)
+            message = QueryMessage(query=query_string, consistency_level=cl)
 
         if trace:
             message.tracing = True

cassandra/query.py

@@ -51,10 +51,11 @@ class Statement(object):
     this will be set to a :class:`.QueryTrace` instance.
     """
 
-    consistency_level = ConsistencyLevel.ONE
+    consistency_level = None
     """
     The :class:`.ConsistencyLevel` to be used for this operation.  Defaults
-    to :attr:`.ConsistencyLevel.ONE`.
+    to :const:`None`, which means that the default consistency level for
+    the Session this is executed in will be used.
     """
 
     _routing_key = None
@@ -119,7 +120,7 @@ class SimpleStatement(Statement):
         return self._query_string
 
     def __str__(self):
-        consistency = ConsistencyLevel.value_to_name[self.consistency_level]
+        consistency = ConsistencyLevel.value_to_name.get(self.consistency_level, 'Not Set')
         return (u'<SimpleStatement query="%s", consistency=%s>' %
                 (self.query_string, consistency))
     __repr__ = __str__
@@ -142,10 +143,10 @@ class PreparedStatement(object):
 
     routing_key_indexes = None
 
-    consistency_level = ConsistencyLevel.ONE
+    consistency_level = None
 
     def __init__(self, column_metadata, query_id, routing_key_indexes, query, keyspace,
-                 consistency_level=ConsistencyLevel.ONE):
+                 consistency_level=None):
         self.column_metadata = column_metadata
         self.query_id = query_id
         self.routing_key_indexes = routing_key_indexes

tests/integration/standard/test_query.py

@@ -17,6 +17,7 @@ try:
 except ImportError:
     import unittest # noqa
 
+from cassandra import ConsistencyLevel
 from cassandra.query import PreparedStatement, BoundStatement, ValueSequence, SimpleStatement
 from cassandra.cluster import Cluster
 from cassandra.decoder import dict_factory
@@ -185,7 +186,7 @@ class PrintStatementTests(unittest.TestCase):
         Highlight the format of printing SimpleStatements
         """
 
-        ss = SimpleStatement('SELECT * FROM test3rf.test')
+        ss = SimpleStatement('SELECT * FROM test3rf.test', consistency_level=ConsistencyLevel.ONE)
         self.assertEqual(str(ss),
                          '<SimpleStatement query="SELECT * FROM test3rf.test", consistency=ONE>')
 
@@ -198,6 +199,7 @@ class PrintStatementTests(unittest.TestCase):
         session = cluster.connect()
 
         prepared = session.prepare('INSERT INTO test3rf.test (k, v) VALUES (?, ?)')
+        prepared.consistency_level = ConsistencyLevel.ONE
 
         self.assertEqual(str(prepared),
                          '<PreparedStatement query="INSERT INTO test3rf.test (k, v) VALUES (?, ?)", consistency=ONE>')