Add an index to the docker_image_id for faster lookup

data/database.py

@@ -386,7 +386,7 @@ class Image(BaseModel):
   # to be globally unique we can't treat them as such for permissions and
   # security reasons. So rather than Repository <-> Image being many to many
   # each image now belongs to exactly one repository.
-  docker_image_id = CharField()
+  docker_image_id = CharField(index=True)
   repository = ForeignKeyField(Repository)
 
   # '/' separated list of ancestory ids, e.g. /1/2/6/7/10/

data/migrations/versions/313d297811c4_add_an_index_to_the_docker_image_id_.py

@@ -0,0 +1,26 @@
+"""Add an index to the docker_image_id field
+
+Revision ID: 313d297811c4
+Revises: 204abf14783d
+Create Date: 2014-11-13 12:40:57.414787
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '313d297811c4'
+down_revision = '204abf14783d'
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import mysql
+
+def upgrade(tables):
+    ### commands auto generated by Alembic - please adjust! ###
+    op.create_index('image_docker_image_id', 'image', ['docker_image_id'], unique=False)
+    ### end Alembic commands ###
+
+
+def downgrade(tables):
+    ### commands auto generated by Alembic - please adjust! ###
+    op.drop_index('image_docker_image_id', table_name='image')
+    ### end Alembic commands ###