Implement a post_syncdb listener which checks database schema consistency

matthiask · matthiask · commit fbd092452170 · 2009-07-16T23:08:35.000+02:00
Since south cannot do non-linear and optional migrations (which would be
necessary to activate and deactivate page extensions) we try at least to
be a little more helpful than simply crashing upon non-existing columns.

The user is informed upon syncdb that several columns might be missing.

Please note that this has not been tested yet with ManyToManyFields --
they obviously do not show up when inspecting the primary table, and the
code does not currently handle this.
diff --git a/feincms/management/checker.py b/feincms/management/checker.py
@@ -0,0 +1,51 @@
+from django.core.management.color import color_style
+from django.db import connection
+
+
+def check_database_schema(cls, module_name):
+    """
+    Returns a function which inspects the database table of the passed class.
+    It checks whether all fields in the model are available on the database
+    too. This is especially helpful for models with an extension mechanism,
+    where the extension might be activated after syncdb has been run for the
+    first time.
+
+    Please note that you have to connect the return value using strong
+    references. Here's an example how to do this:
+
+    signals.post_syncdb.connect(check_database_schema(Page, __name__),
+                                weak=False)
+    """
+
+    def _fn(sender, **kwargs):
+        if sender.__name__ != module_name:
+            return
+
+        cursor = connection.cursor()
+
+        existing_columns = [row[0] for row in \
+            connection.introspection.get_table_description(cursor, cls._meta.db_table)]
+
+        missing_columns = []
+
+        for field in cls._meta.fields:
+            if field.column not in existing_columns:
+                missing_columns.append(field)
+
+        if not missing_columns:
+            return
+
+        style = color_style()
+
+        print style.ERROR('The following columns seem to be missing in the database table %s:' % cls._meta.db_table)
+        for field in missing_columns:
+            print u'%s:%s%s' % (
+                style.SQL_KEYWORD(field.column),
+                ' ' * (25 - len(field.column)),
+                u'%s.%s' % (field.__class__.__module__, field.__class__.__name__),
+                )
+
+        print style.NOTICE('\nPlease consult the output of `python manage.py sql %s` to find out what the correct column types are.\n' % (
+            cls._meta.app_label,
+            ))
+    return _fn
diff --git a/feincms/module/blog/models.py b/feincms/module/blog/models.py
@@ -3,11 +3,12 @@
 from django.conf import settings
 from django.contrib import admin
 from django.db import models
-from django.db.models import Q
+from django.db.models import Q, signals
 from django.http import Http404
 from django.utils.translation import ugettext_lazy as _
 
 from feincms.admin import editor
+from feincms.management.checker import check_database_schema
 from feincms.models import Base
 from feincms.utils import get_object
 
@@ -61,6 +62,8 @@ def register_extensions(cls, *extensions):
             fn(cls, EntryAdmin)
             cls._feincms_extensions.add(ext)
 
+signals.post_syncdb.connect(check_database_schema(Entry, __name__), weak=False)
+
 
 class EntryAdmin(editor.ItemEditor, admin.ModelAdmin):
     date_hierarchy = 'published_on'
diff --git a/feincms/module/page/models.py b/feincms/module/page/models.py
@@ -6,7 +6,7 @@
 from django.contrib import admin
 from django.conf import settings
 from django.db import models
-from django.db.models import Q
+from django.db.models import Q, signals
 from django.http import Http404, HttpResponseRedirect
 from django.utils.translation import ugettext_lazy as _
 from django.core.urlresolvers import reverse
@@ -15,6 +15,7 @@
 
 from feincms.admin import editor
 from feincms.admin.editor import django_boolean_icon
+from feincms.management.checker import check_database_schema
 from feincms.models import Region, Template, Base, ContentProxy
 from feincms.utils import get_object
 
@@ -250,6 +251,7 @@ def register_extensions(cls, *extensions):
                                  Page.frontendediting_request_processor,
                                  Page.redirect_request_processor)
 
+signals.post_syncdb.connect(check_database_schema(Page, __name__), weak=False)
 
 
 class PageAdmin(editor.ItemEditor, editor.TreeEditor):
