Add main_transcoding_progress column migration

This field is required to store the progress of the default
resolution of the media. So, we now store the total progress of transcoding
the video in 'transcoding_progress' and progress of transcoding the default
resolution in 'main_transcoding_progress'.

mediagoblin/db/migrations/versions/cc3651803714_add_main_transcoding_progress_column_to_.py

@@ -0,0 +1,28 @@
+"""add main transcoding progress column to MediaEntry
+
+Revision ID: cc3651803714
+Revises: 228916769bd2
+Create Date: 2017-08-21 23:33:01.401589
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = 'cc3651803714'
+down_revision = '228916769bd2'
+branch_labels = None
+depends_on = None
+
+from alembic import op
+import sqlalchemy as sa
+
+
+def upgrade():
+	"""
+	Addition of main_transcoding_progress is required to save the progress of the
+	default resolution (other than the total progress of the video).
+	"""
+	op.add_column('core__media_entries', sa.Column('main_transcoding_progress', sa.Float(), default=0))
+
+
+def downgrade():
+    pass

mediagoblin/db/models.py

@@ -543,6 +543,7 @@ class MediaEntry(Base, MediaEntryMixin, CommentingMixin):
     fail_metadata = Column(JSONEncoded)
 
     transcoding_progress = Column(Float, default=0)
+    main_transcoding_progress = Column(Float, default=0)
 
     queued_media_file = Column(PathTupleWithSlashes)