From 94ed2f7c157a4ad2be6423c5fb4a1a99f131c0e0 Mon Sep 17 00:00:00 2001
From: Scott Walton <scott.walton@mypebble.co.uk>
Date: Thu, 17 Jul 2014 11:37:42 +0100
Subject: [PATCH] Added a clear command so we can remove views before running a
 migration

---
 .../management/commands/clear_pgviews.py      | 28 +++++++++++++++
 django_pgviews/view.py                        | 34 +++++++++++++++++++
 setup.py                                      |  2 +-
 .../test_project/viewtest/tests.py            |  9 +++++
 4 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 django_pgviews/management/commands/clear_pgviews.py

diff --git a/django_pgviews/management/commands/clear_pgviews.py b/django_pgviews/management/commands/clear_pgviews.py
new file mode 100644
index 0000000..6cc5a3e
--- /dev/null
+++ b/django_pgviews/management/commands/clear_pgviews.py
@@ -0,0 +1,28 @@
+from optparse import make_option
+import logging
+
+from django.core.management.base import NoArgsCommand
+from django.db import models
+
+from django_pgviews.view import clear_views
+
+
+log = logging.getLogger('django_pgviews.sync_pgviews')
+
+
+class Command(NoArgsCommand):
+    help = """Clear Postgres views. Use this before running a migration"""
+
+    def handle_noargs(self, **options):
+        """
+        """
+        for module in models.get_apps():
+            for status, view_cls, python_name in clear_views(module):
+                if status == 'DROPPED':
+                    msg = 'dropped'
+                else:
+                    msg = 'not dropped'
+                log.info("%(python_name)s (%(view_name)s): %(msg)s" % {
+                    'python_name': python_name,
+                    'view_name': view_cls._meta.db_table,
+                    'msg': msg})
diff --git a/django_pgviews/view.py b/django_pgviews/view.py
index f362b9c..5c48659 100644
--- a/django_pgviews/view.py
+++ b/django_pgviews/view.py
@@ -126,6 +126,40 @@ def create_view(connection, view_name, view_query, update=True, force=False):
         cursor_wrapper.close()
 
 
+def clear_views(models_module):
+    """Remove the database views for a given models_module."""
+    for name, view_cls in vars(models_module).iteritems():
+        if not (isinstance(view_cls, type) and
+                issubclass(view_cls, View) and
+                hasattr(view_cls, 'sql')):
+            continue
+
+        try:
+            cleared = clear_view(
+                connection, view_cls._meta.db_table)
+        except Exception, exc:
+            exc.view_cls = view_cls
+            exc.python_name = models_module.__name__ + '.' + name
+            raise
+        else:
+            yield cleared, view_cls, models_module.__name__ + '.' + name
+
+
+def clear_view(connection, view_name):
+    """
+    Remove a named view on connection.
+    """
+    cursor_wrapper = connection.cursor()
+    cursor = cursor_wrapper.cursor
+    try:
+        cursor.execute('DROP VIEW IF EXISTS {0}'.format(view_name))
+
+        transaction.commit_unless_managed()
+    finally:
+        cursor_wrapper.close()
+    return u'DROPPED'.format(view=view_name)
+
+
 class View(models.Model):
 
     """Helper for exposing Postgres views as Django models."""
diff --git a/setup.py b/setup.py
index 3b1a840..48f3e34 100644
--- a/setup.py
+++ b/setup.py
@@ -2,7 +2,7 @@
 
 setup(
     name='django-pgviews',
-    version='0.0.2',
+    version='0.0.3',
     description="Create and manage Postgres SQL Views in Django",
     author='Scott Walton',
     author_email='scott.walton@mypebble.co.uk',
diff --git a/tests/test_project/test_project/viewtest/tests.py b/tests/test_project/test_project/viewtest/tests.py
index 53faacc..76e4662 100644
--- a/tests/test_project/test_project/viewtest/tests.py
+++ b/tests/test_project/test_project/viewtest/tests.py
@@ -21,6 +21,15 @@ def test_views_have_been_created(self):
             count, = cur.fetchone()
             self.assertEqual(count, 3)
 
+    def test_clear_views(self):
+        call_command('clear_pgviews', *[], **{})
+        with closing(connection.cursor()) as cur:
+            cur.execute('''SELECT COUNT(*) FROM pg_views
+                        WHERE viewname LIKE 'viewtest_%';''')
+
+            count, = cur.fetchone()
+            self.assertEqual(count, 0)
+
     def test_wildcard_projection_gets_all_fields_from_projected_model(self):
         foo_user = auth.models.User.objects.create(
             username='foo', is_superuser=True)