411: Add relationship and backrefs to media_data tables.

Adding proper relationship()s and especially backref()s
will delete media_data rows along with the main MediaEntry.
This fixes #411.

mediagoblin/media_types/ascii/models.py

@@ -18,8 +18,8 @@
 from mediagoblin.db.sql.base import Base
 
 from sqlalchemy import (
-    Column, Integer, Unicode, UnicodeText, DateTime, Boolean, ForeignKey,
-    UniqueConstraint)
+    Column, Integer, ForeignKey)
+from sqlalchemy.orm import relationship, backref
 
 
 class AsciiData(Base):
@@ -28,6 +28,8 @@ class AsciiData(Base):
     # The primary key *and* reference to the main media_entry
     media_entry = Column(Integer, ForeignKey('core__media_entries.id'),
         primary_key=True)
+    get_media_entry = relationship("MediaEntry",
+        backref=backref("ascii__media_data", cascade="all, delete-orphan"))
 
 
 DATA_MODEL = AsciiData

mediagoblin/media_types/image/models.py

@@ -19,6 +19,7 @@ from mediagoblin.db.sql.base import Base
 
 from sqlalchemy import (
     Column, Integer, Float, ForeignKey)
+from sqlalchemy.orm import relationship, backref
 from mediagoblin.db.sql.extratypes import JSONEncoded
 
 
@@ -28,6 +29,9 @@ class ImageData(Base):
     # The primary key *and* reference to the main media_entry
     media_entry = Column(Integer, ForeignKey('core__media_entries.id'),
         primary_key=True)
+    get_media_entry = relationship("MediaEntry",
+        backref=backref("image__media_data", cascade="all, delete-orphan"))
+
     width = Column(Integer)
     height = Column(Integer)
     exif_all = Column(JSONEncoded)

mediagoblin/media_types/video/models.py

@@ -19,6 +19,7 @@ from mediagoblin.db.sql.base import Base
 
 from sqlalchemy import (
     Column, Integer, SmallInteger, ForeignKey)
+from sqlalchemy.orm import relationship, backref
 
 
 class VideoData(Base):
@@ -27,6 +28,9 @@ class VideoData(Base):
     # The primary key *and* reference to the main media_entry
     media_entry = Column(Integer, ForeignKey('core__media_entries.id'),
         primary_key=True)
+    get_media_entry = relationship("MediaEntry",
+        backref=backref("video__media_data", cascade="all, delete-orphan"))
+
     width = Column(SmallInteger)
     height = Column(SmallInteger)