Support model inheritance

Author: jpic

.travis.yml

@@ -19,7 +19,7 @@ env:
   - TOXENV=py36-django20-sqlite
   - TOXENV=py36-django20-mysql
   - TOXENV=py36-django20-postgresql
-  - TOXENV=checkqa
+  - TOXENV=qa
 install:
 - pip install -U pip
 - pip install tox codecov

dbdiff/sequence.py

@@ -9,7 +9,8 @@ def pk_sequence_get(model):
             continue
         if not isinstance(field, models.AutoField):
             continue
-        return field.db_column or field.column
+        return (field.db_column or field.column, field.model._meta.db_table)
+    return (None, None)
 
 
 def sequence_reset(model):
@@ -21,7 +22,7 @@ def sequence_reset(model):
     supporting pre-existing models which could have been created by a
     migration.
     """
-    pk_field = pk_sequence_get(model)
+    pk_field, table = pk_sequence_get(model)
     if not pk_field:
         return
 
@@ -45,12 +46,12 @@ def sequence_reset(model):
         cursor = connection.cursor()
         cursor.execute(
             'SELECT MAX({column}) + 1 FROM {table}'.format(
-                column=pk_field, table=model._meta.db_table
+                column=pk_field, table=table
             )
         )
         result = cursor.fetchone()[0] or 0
         reset = 'ALTER TABLE {table} AUTO_INCREMENT = %s' % result
 
     connection.cursor().execute(
-        reset.format(column=pk_field, table=model._meta.db_table)
+        reset.format(column=pk_field, table=table)
     )

dbdiff/tests/inheritance/__init__.py

@@ -0,0 +1 @@
+"""Test app for model inheritance."""

dbdiff/tests/inheritance/models.py

@@ -0,0 +1,9 @@
+from django.db import models
+
+
+class Parent(models.Model):
+    pass
+
+
+class Child(Parent):
+    name = models.CharField(max_length=50)

dbdiff/tests/project/settings.py

@@ -41,6 +41,7 @@
 
     'dbdiff.tests.decimal_test',
     'dbdiff.tests.nonintpk',
+    'dbdiff.tests.inheritance',
 )
 
 MIDDLEWARE_CLASSES = (

dbdiff/tests/test_mixin.json

@@ -63,12 +63,28 @@
     "model": "contenttypes.contenttype",
     "pk": 8
 },
+{
+    "fields": {
+        "app_label": "inheritance",
+        "model": "parent"
+    },
+    "model": "contenttypes.contenttype",
+    "pk": 9
+},
+{
+    "fields": {
+        "app_label": "inheritance",
+        "model": "child"
+    },
+    "model": "contenttypes.contenttype",
+    "pk": 10
+},
 {
     "fields": {
         "app_label": "",
         "model": ""
     },
     "model": "contenttypes.contenttype",
-    "pk": 9
+    "pk": 11
 }
 ]

dbdiff/tests/test_plugin.py

@@ -1,4 +1,5 @@
 from dbdiff.tests.decimal_test.models import TestModel as DecimalModel
+from dbdiff.tests.inheritance.models import Child, Parent
 from dbdiff.tests.nonintpk.models import Nonintpk
 
 import pytest
@@ -19,3 +20,15 @@ def test_still_first_pk():
 @pytest.mark.dbdiff(models=[DecimalModel, Nonintpk])
 def test_doesnt_reset_nonintpk_which_would_fail():
     assert DecimalModel.objects.count() == 0
+
+
+@pytest.mark.dbdiff(models=[Child])
+def test_inheritance_sequence_reset():
+    assert Child.objects.count() == 0
+    assert Child.objects.create(name='1').pk == 1
+
+
+@pytest.mark.dbdiff(models=[Child])
+def test_inheritance_sequence_reset_again():
+    assert Parent.objects.count() == 0
+    assert Child.objects.create(name='1').pk == 1

tox.ini

@@ -30,7 +30,7 @@ setenv =
     mysql: DJANGO_SETTINGS_MODULE=dbdiff.tests.project.settings_mysql
 passenv = TEST_* DBDIFF_*
 
-[testenv:checkqa]
+[testenv:qa]
 basepython = python2.7
 commands =
     flake8 --show-source --exclude tests --max-complexity=7 --ignore=D203 dbdiff