Avoid unnecessary database reads

 Use the cached function isInDatabase rather than readFromDatabase to
 avoid unnecessary read operations on the database.

 Currently, readFromDatabase is usually called only once during instance
 livetime. But after I455b41c8b8d918f4c34f6c115194d227a8394e0a has bben
 merged chances are that it's called twice.

Change-Id: I6434195ad1d323a578a8fdca1b4555e11ab30a15
Merge "Avoid unnecessary database reads"