Retroactive indexing in Google Cloud Datastore

Question

There are many properties in my model that I currently don\'t need indexed but can imagine I might want indexed at some unknown point in the future. If I explicitly set

Answer 1

To index properties of existing entities (as per the documentation):

1. Retrieve (get) the entity from the Datastore.
2. Write (put) the entity back to the Datastore.

didn't work for me. I employed appengine-mapreduce library and wrote a MapOnlyMapper using DatastoreMutationPool for indexing all the existing entities in Datastore.

Lets assume the property name was unindexed and I want to index this in all the existing entities. What I had to do is:

@Override
public void map(Entity value) {
    String property = "name";
    Object existingValue = value.getProperty(property);
    value.setIndexedProperty(property, existingValue);
    datastoreMutationPool.put(value);
}

Essentially, you will have to set the property as indexed property using setIndexedProperty(prop, value) and then save (put) the entity.

I know I am very late in posting an answer. I thought I could help someone who might be struggling with this problem.