value: 1 The index is being created, and cannot be used by queries.
There is an active long-running operation for the index.
The index is updated when writing an entity.
Some index data may exist.
READY
value: 2 The index is ready to be used.
The index is updated when writing an entity.
The index is fully populated from all stored entities it applies to.
DELETING
value: 3 The index is being deleted, and cannot be used by queries.
There is an active long-running operation for the index.
The index is not updated when writing an entity.
Some index data may exist.
ERROR
value: 4 The index was being created or deleted, but something went wrong.
The index cannot by used by queries.
There is no active long-running operation for the index,
and the most recently finished long-running operation failed.
The index is not updated when writing an entity.
Some index data may exist.