NDB: Sort query results

Question

In App Engine NDB, I am querying entities that have a repeated property. I would like to order the result by the length of the array representing that property.

What I wish I could do:

Entity.query(...).order(len(Entity.repeatedProp))

Answer 1

You'll need to add an ndb.IntegerProperty() to your entity where you will store the length of the repeated property. Every time you change your repeated property, you'll need to update the stored length. Then you sort based on that stored length.

You could probably use a computed property, but I've never used one of those so I'm not sure.