The new flexible environment datastore interface does not seem to support IN operation when running a query. I hope that I'm wrong, and if so, how can one use an IN operator in the new Java interface of Datastore?
A query like - WHERE color IN('RED', 'BLACK'), it is not supported by the Datastore (server side). Same is the case with OR operator (e.g. WHERE color='RED' OR color='BLACK'). Some client APIs have added this functionality by splitting the query into multiple and then merging the results from each query. The new google-cloud-java API does not support this yet. For now, you would have to run multiple queries for each value in the IN clause and merge the results.