adding single instance delete method and supporting unit test

adding column type stubs
updating readme

README.md

@@ -1,16 +1,22 @@
 cassandraengine
 ===============
 
-Django ORM / Mongoengine style ORM for Cassandra
+Python Cassandra ORM in the style of django / mongoengine
 
 In it's current state you can define column families, create and delete column families
 based on your model definiteions, save models and retrieve models by their primary keys.
 
-That's about it. Also, there are only 2 tests and the CQL stuff is very simplistic at this point.
+That's about it. Also, the CQL stuff is pretty simple at this point.
 
 ##TODO
+* Complex queries (class Q(object))
+* Match column names to mongoengine field names?
+* mongoengine fields? URLField, EmbeddedDocument, ListField, DictField
+* column ttl?
+* ForeignKey/DBRef fields?
 * dynamic column support
-* return None when row isn't found in find()
 * tests
 * query functionality
 * nice column and model class __repr__
+
+

cassandraengine/columns.py

@@ -106,6 +106,9 @@ class Integer(BaseColumn):
 
 class DateTime(BaseColumn):
     db_type = 'timestamp'
+    def __init__(self, **kwargs):
+        super(DateTime, self).__init__(**kwargs)
+        raise NotImplementedError
 
 class UUID(BaseColumn):
     """
@@ -153,4 +156,23 @@ class Float(BaseColumn):
 class Decimal(BaseColumn):
     db_type = 'decimal'
     #TODO: this
+    def __init__(self, **kwargs):
+        super(DateTime, self).__init__(**kwargs)
+        raise NotImplementedError
 
+class Counter(BaseColumn):
+    def __init__(self, **kwargs):
+        super(DateTime, self).__init__(**kwargs)
+        raise NotImplementedError
+
+#TODO: research supercolumns
+#http://wiki.apache.org/cassandra/DataModel
+class List(BaseColumn):
+    def __init__(self, **kwargs):
+        super(DateTime, self).__init__(**kwargs)
+        raise NotImplementedError
+
+class Dict(BaseColumn):
+    def __init__(self, **kwargs):
+        super(DateTime, self).__init__(**kwargs)
+        raise NotImplementedError

cassandraengine/manager.py

@@ -22,16 +22,19 @@ class Manager(object):
         cf_name = cf_name[-48:]
         return cf_name
 
-    def column_family_definition(self):
+    def __call__(self, **kwargs):
         """
-        Generates a definition used for tale creation
+        filter shortcut
         """
+        return self.filter(**kwargs)
 
     def find(self, pk):
         """
         Returns the row corresponding to the primary key value given
         """
         values = QuerySet(self.model).find(pk)
+        if values is None: return
+
         #change the column names to model names
         #in case they are different
         field_dict = {}
@@ -55,6 +58,10 @@ class Manager(object):
     def create(self, **kwargs):
         return self.model(**kwargs).save()
 
+    def delete(self, **kwargs):
+        pass
+
+    #----single instance methods----
     def _save_instance(self, instance):
         """
         The business end of save, this is called by the models
@@ -63,18 +70,15 @@ class Manager(object):
         """
         QuerySet(self.model).save(instance)
 
+    def _delete_instance(self, instance):
+        """
+        Deletes a single instance
+        """
+        QuerySet(self.model).delete_instance(instance)
+
+    #----column family create/delete----
     def _create_column_family(self):
         QuerySet(self.model)._create_column_family()
 
     def _delete_column_family(self):
         QuerySet(self.model)._delete_column_family()
-
-    def delete(self, **kwargs):
-        pass
-
-    def __call__(self, **kwargs):
-        """
-        filter shortcut
-        """
-        return self.filter(**kwargs)
-

cassandraengine/models.py

@@ -65,7 +65,8 @@ class BaseModel(object):
         return self
 
     def delete(self):
-        pass
+        """ Deletes this instance """
+        self.objects._delete_instance(self)
 
 
 class ModelMetaClass(type):

cassandraengine/query.py

@@ -42,7 +42,7 @@ class QuerySet(object):
         """
         cur = self._cursor
         values = cur.fetchone()
-        if values is None: return None
+        if values is None: return
         names = [i[0] for i in cur.description]
         value_dict = dict(zip(names, values))
         return value_dict
@@ -64,15 +64,12 @@ class QuerySet(object):
         return QuerySet(self.model, query_args=qargs)
 
     def exclude(self, **kwargs):
-        """
+        """ Need to invert the logic for all kwargs """
-        Need to invert the logic for all kwargs
-        """
         pass
 
     def count(self):
-        """
+        """ Returns the number of rows matched by this query """
-        Returns the number of rows matched by this query
+        qs = 'SELECT COUNT(*) FROM {}'.format(self.column_family_name)
-        """
 
     def find(self, pk):
         """
@@ -128,6 +125,23 @@ class QuerySet(object):
         cur = conn.cursor()
         cur.execute(qs, field_values)
 
+    #----delete---
+    def delete(self):
+        """
+        Deletes the contents of a query
+        """
+
+    def delete_instance(self, instance):
+        """ Deletes one instance """
+        pk_name = self.model._pk_name
+        qs = ['DELETE FROM {}'.format(self.column_family_name)]
+        qs += ['WHERE {0}=:{0}'.format(pk_name)]
+        qs = ' '.join(qs)
+
+        conn = get_connection()
+        cur = conn.cursor()
+        cur.execute(qs, {pk_name:instance.pk})
+
     def _create_column_family(self):
         #construct query string
         qs = ['CREATE TABLE {}'.format(self.column_family_name)]

cassandraengine/tests/model/test_model_io.py

@@ -38,6 +38,15 @@ class TestModelIO(BaseCassEngTestCase):
         tm2 = TestModel.objects.find(tm.pk)
         self.assertEquals(tm.count, tm2.count)
 
+    def test_model_deleting_works_properly(self):
+        """
+        Tests that an instance's delete method deletes the instance
+        """
+        tm = TestModel.objects.create(count=8, text='123456789')
+        tm.delete()
+        tm2 = TestModel.objects.find(tm.pk)
+        self.assertIsNone(tm2)
+
     def test_nullable_columns_are_saved_properly(self):
         """
         Tests that nullable columns save without any trouble