openstack/deb-python-cassandra-driver
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Merge pull request #488 from datastax/336

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PYTHON-336 - Expose LWT results in cqlengine LWTException
This commit is contained in:
Adam Holmberg
2016-02-24 08:26:57 -06:00
parent f1e49230eb 5e102605cd
commit 853a77ad6f
8 changed files with 117 additions and 19 deletions
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1
CHANGELOG.rst
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@@ -6,6 +6,7 @@ Features
* Pass name of server auth class to AuthProvider (PYTHON-454)
* Surface schema agreed flag for DDL statements (PYTHON-458)
* Automatically convert float and int to Decimal on serialization (PYTHON-468)
* Expose prior state information via cqlengine LWTException (github #343)
Bug Fixes
---------

25
cassandra/cluster.py
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@@ -70,8 +70,8 @@ from cassandra.pool import (Host, _ReconnectionHandler, _HostReconnectionHandler
HostConnectionPool, HostConnection,
NoConnectionsAvailable)
from cassandra.query import (SimpleStatement, PreparedStatement, BoundStatement,
BatchStatement, bind_params, QueryTrace, Statement,
named_tuple_factory, dict_factory, FETCH_SIZE_UNSET)
BatchStatement, bind_params, QueryTrace,
named_tuple_factory, dict_factory, tuple_factory, FETCH_SIZE_UNSET)
def _is_eventlet_monkey_patched():
@@ -3409,3 +3409,24 @@ class ResultSet(object):
See :meth:`.ResponseFuture.get_all_query_traces` for details.
"""
return self.response_future.get_all_query_traces(max_wait_sec_per)
@property
def was_applied(self):
"""
For LWT results, returns whether the transaction was applied.
Result is indeterminate if called on a result that was not an LWT request.
Only valid when one of tne of the internal row factories is in use.
"""
if self.response_future.row_factory not in (named_tuple_factory, dict_factory, tuple_factory):
raise RuntimeError("Cannot determine LWT result with row factory %s" % (self.response_future.row_factsory,))
if len(self.current_rows) != 1:
raise RuntimeError("LWT result should have exactly one row. This has %d." % (len(self.current_rows)))
row = self.current_rows[0]
if isinstance(row, tuple):
return row[0]
else:
return row['[applied]']

24
cassandra/cqlengine/query.py
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@@ -40,7 +40,17 @@ class IfNotExistsWithCounterColumn(CQLEngineException):
class LWTException(CQLEngineException):
pass
"""Lightweight transaction exception.
This exception will be raised when a write using an `IF` clause could not be
applied due to existing data violating the condition. The existing data is
available through the ``existing`` attribute.
:param existing: The current state of the data which prevented the write.
"""
def __init__(self, existing):
super(LWTException, self).__init__(self)
self.existing = existing
class DoesNotExist(QueryException):
@@ -53,12 +63,14 @@ class MultipleObjectsReturned(QueryException):
def check_applied(result):
"""
check if result contains some column '[applied]' with false value,
if that value is false, it means our light-weight transaction didn't
applied to database.
Raises LWTException if it looks like a failed LWT request.
"""
if result and '[applied]' in result[0] and not result[0]['[applied]']:
raise LWTException('')
try:
applied = result.was_applied
except Exception:
applied = True # result was not LWT form
if not applied:
raise LWTException(result[0])
class AbstractQueryableColumn(UnicodeMixin):

10
docs/api/cassandra/cqlengine/models.rst
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@@ -48,7 +48,6 @@ Model
See the `list of supported table properties for more information
<http://www.datastax.com/documentation/cql/3.1/cql/cql_reference/tabProp.html>`_.
.. attribute:: __options__
For example:
@@ -89,7 +88,7 @@ Model
object is determined by its primary key(s). And please note using this flag
would incur performance cost.
if the insertion didn't applied, a LWTException exception would be raised.
If the insertion isn't applied, a :class:`~cassandra.cqlengine.query.LWTException` is raised.
.. code-block:: python
@@ -97,7 +96,7 @@ Model
TestIfNotExistsModel.if_not_exists().create(id=id, count=9, text='111111111111')
except LWTException as e:
# handle failure case
print e.existing # existing object
print e.existing # dict containing LWT result fields
This method is supported on Cassandra 2.0 or later.
@@ -111,7 +110,7 @@ Model
Simply specify the column(s) and the expected value(s). As with if_not_exists,
this incurs a performance cost.
If the insertion isn't applied, a LWTException is raised
If the insertion isn't applied, a :class:`~cassandra.cqlengine.query.LWTException` is raised.
.. code-block:: python
@@ -119,7 +118,8 @@ Model
try:
t.iff(count=5).update('other text')
except LWTException as e:
# handle failure
# handle failure case
print e.existing # existing object
.. automethod:: get

1
docs/api/cassandra/cqlengine/query.rst
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@@ -40,3 +40,4 @@ The methods here are used to filter, order, and constrain results.
.. autoclass:: MultipleObjectsReturned
.. autoclass:: LWTException

19
tests/integration/cqlengine/test_ifnotexists.py
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@@ -81,9 +81,17 @@ class IfNotExistsInsertTests(BaseIfNotExistsTest):
id = uuid4()
TestIfNotExistsModel.create(id=id, count=8, text='123456789')
with self.assertRaises(LWTException):
with self.assertRaises(LWTException) as assertion:
TestIfNotExistsModel.if_not_exists().create(id=id, count=9, text='111111111111')
self.assertEqual(assertion.exception.existing, {
'count': 8,
'id': id,
'text': '123456789',
'[applied]': False,
})
q = TestIfNotExistsModel.objects(id=id)
self.assertEqual(len(q), 1)
@@ -117,9 +125,16 @@ class IfNotExistsInsertTests(BaseIfNotExistsTest):
b = BatchQuery()
TestIfNotExistsModel.batch(b).if_not_exists().create(id=id, count=9, text='111111111111')
with self.assertRaises(LWTException):
with self.assertRaises(LWTException) as assertion:
b.execute()
self.assertEqual(assertion.exception.existing, {
'count': 8,
'id': id,
'text': '123456789',
'[applied]': False,
})
q = TestIfNotExistsModel.objects(id=id)
self.assertEqual(len(q), 1)

29
tests/integration/cqlengine/test_transaction.py
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@@ -29,8 +29,9 @@ from cassandra.cqlengine.statements import TransactionClause
from tests.integration.cqlengine.base import BaseCassEngTestCase
from tests.integration import CASSANDRA_VERSION
class TestTransactionModel(Model):
id = columns.UUID(primary_key=True, default=lambda:uuid4())
id = columns.UUID(primary_key=True, default=uuid4)
count = columns.Integer()
text = columns.Text(required=False)
@@ -71,7 +72,14 @@ class TestTransaction(BaseCassEngTestCase):
t = TestTransactionModel.create(text='blah blah')
t.text = 'new blah'
t = t.iff(text='something wrong')
self.assertRaises(LWTException, t.save)
with self.assertRaises(LWTException) as assertion:
t.save()
self.assertEqual(assertion.exception.existing, {
'text': 'blah blah',
'[applied]': False,
})
def test_blind_update(self):
t = TestTransactionModel.create(text='blah blah')
@@ -89,7 +97,13 @@ class TestTransaction(BaseCassEngTestCase):
t.text = 'something else'
uid = t.id
qs = TestTransactionModel.objects(id=uid).iff(text='Not dis!')
self.assertRaises(LWTException, qs.update, text='this will never work')
with self.assertRaises(LWTException) as assertion:
qs.update(text='this will never work')
self.assertEqual(assertion.exception.existing, {
'text': 'blah blah',
'[applied]': False,
})
def test_transaction_clause(self):
tc = TransactionClause('some_value', 23)
@@ -109,7 +123,14 @@ class TestTransaction(BaseCassEngTestCase):
b = BatchQuery()
updated.batch(b).iff(count=6).update(text='and another thing')
self.assertRaises(LWTException, b.execute)
with self.assertRaises(LWTException) as assertion:
b.execute()
self.assertEqual(assertion.exception.existing, {
'id': id,
'count': 5,
'[applied]': False,
})
updated = TestTransactionModel.objects(id=id).first()
self.assertEqual(updated.text, 'something else')

27
tests/unit/test_resultset.py
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@@ -11,6 +11,7 @@
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from cassandra.query import named_tuple_factory, dict_factory, tuple_factory
try:
import unittest2 as unittest
@@ -161,3 +162,29 @@ class ResultSetTests(unittest.TestCase):
def test_bool(self):
self.assertFalse(ResultSet(Mock(has_more_pages=False), []))
self.assertTrue(ResultSet(Mock(has_more_pages=False), [1]))
def test_was_applied(self):
# unknown row factory raises
with self.assertRaises(RuntimeError):
ResultSet(Mock(), []).was_applied
response_future = Mock(row_factory=named_tuple_factory)
# no row
with self.assertRaises(RuntimeError):
ResultSet(response_future, []).was_applied
# too many rows
with self.assertRaises(RuntimeError):
ResultSet(response_future, [tuple(), tuple()]).was_applied
# various internal row factories
for row_factory in (named_tuple_factory, tuple_factory):
for applied in (True, False):
rs = ResultSet(Mock(row_factory=row_factory), [(applied,)])
self.assertEqual(rs.was_applied, applied)
row_factory = dict_factory
for applied in (True, False):
rs = ResultSet(Mock(row_factory=row_factory), [{'[applied]': applied}])
self.assertEqual(rs.was_applied, applied)