The App Engine SDK developer server can automatically create datastore indexes for your application – just run the datastore querying code within the dev server. But sometimes that isn’t possible.
In that case, you can hand-write your index settings. Here is an example of a simple index.yaml file. It indexes all entities with a kind of Fact, on the property Approved and sorts on the property Add_date in descending order.
indexes:
- kind: Fact
ancestor: no
properties:
- name: Approved
- name: Add_date
direction: desc
index.yaml goes in the root directory of your application.