Restrictions When Using Google Datastore
When using NoSQL selection rules at a Google Datastore NoSQL database, the following restrictions apply:
- Use of OR is not supported. 
- Use of the ≠, Exists, and Does not exist operators is not supported. 
- If more than one column is referenced in a rule’s criteria, a Datastore composite index covering the columns in question must be configured prior to rule execution. 
If any of the above are not observed, rule execution will fail.
