Support model class inheritance

src/infi/clickhouse_orm/models.py

@@ -10,8 +10,13 @@ class ModelBase(type):
 
     def __new__(cls, name, bases, attrs):
         new_cls = super(ModelBase, cls).__new__(cls, name, bases, attrs)
+        # Collect fields from parent classes
+        base_fields = []
+        for base in bases:
+            if isinstance(base, ModelBase):
+                base_fields += base._fields
         # Build a list of fields, in the order they were listed in the class
-        fields = [item for item in attrs.items() if isinstance(item[1], Field)]
+        fields = base_fields + [item for item in attrs.items() if isinstance(item[1], Field)]
         fields.sort(key=lambda item: item[1].creation_counter)
         setattr(new_cls, '_fields', fields)
         return new_cls

tests/test_inheritance.py

@@ -0,0 +1,52 @@
+import unittest
+import datetime
+import pytz
+
+from infi.clickhouse_orm.models import Model
+from infi.clickhouse_orm.fields import *
+from infi.clickhouse_orm.engines import *
+
+
+class InheritanceTestCase(unittest.TestCase):
+
+    def assertFieldNames(self, model_class, names):
+        self.assertEquals(names, [name for name, field in model_class._fields])
+
+    def test_field_inheritance(self):
+        self.assertFieldNames(ParentModel, ['date_field', 'int_field'])
+        self.assertFieldNames(Model1, ['date_field', 'int_field', 'string_field'])
+        self.assertFieldNames(Model2, ['date_field', 'int_field', 'float_field'])
+
+    def test_create_table_sql(self):
+        sql1 = ParentModel.create_table_sql('default')
+        sql2 = Model1.create_table_sql('default')
+        sql3 = Model2.create_table_sql('default')
+        self.assertNotEqual(sql1, sql2)
+        self.assertNotEqual(sql1, sql3)
+        self.assertNotEqual(sql2, sql3)
+
+    def test_get_field(self):
+        self.assertIsNotNone(ParentModel().get_field('date_field'))
+        self.assertIsNone(ParentModel().get_field('string_field'))
+        self.assertIsNotNone(Model1().get_field('date_field'))
+        self.assertIsNotNone(Model1().get_field('string_field'))
+        self.assertIsNone(Model1().get_field('float_field'))
+
+
+class ParentModel(Model):
+
+    date_field = DateField()
+    int_field = Int32Field()
+
+    engine = MergeTree('date_field', ('int_field', 'date_field'))
+
+
+class Model1(ParentModel):
+
+    string_field = StringField()
+
+
+class Model2(ParentModel):
+
+    float_field = Float32Field()
+