DataRow a map that holds values retrieved from the database for a given query row.
DataRows are used to cache raw database data and as a reference point for tracking
PersistentObject changes.
Creates a DataRow that contains only the keys that have values that differ between
this object and row parameter. Diff values are taken from the
row parameter. It is assumed that key sets are compatible in both rows
(e.g. they represent snapshots for the same entity). Returns null if no differences
are found.
Returns an ObjectId of an object on the other side of the to-one relationship, for
this DataRow representing a source of relationship. Returns null if snapshot FK
columns indicate a null to-one relationship.