Question

I have a Model with a big blob property User.image
Having this property in my model made my queries take too much time and go over the deadline so I decided to move that property into another model – UserData – who’s parent is the User.

However, existing model instances that are already in the datastore still contain that image data even though the Model definition no longer contains that property.

Is there any, way to delete that data from the User instances?

Answer 1

The answer to your question is documented here : https://developers.google.com/appengine/articles/update_schema

Copy/paste from the “Removing Deleted Properties from the Datastore” section :

If you remove a property from your
model, you will find that existing
entities still have the property. It
will still be shown in the admin
console and will still be present in
the datastore. To really clean out the
old data, you need to cycle through
your entities and remove the data from
each one.

1. Make sure you have removed the properties from the model definition.
2. If your model class inherits from db.Model, temporarily switch it
   to inherit from db.Expando. (db.Model
   instances can’t be modified
   dynamically, which is what we need to
   do in the next step.)
3. Cycle through existing entities (like described above). For each
   entity, use delattr to delete the
   obsolete property and then save the
   entity.
4. If your model originally inherited from db.Model, don’t forget
   to change it back after updating all
   the data.