Maps result-sets to specific contextual data related to processing that result set
Implementation note: internally an IdentityMap is used to maintain the mappings mainly because I'd
rather not be dependent upon potentially bad Object.equals(java.lang.Object) and Object.hashCode() implementations on
the JDBC result sets
Considering the JDBC-redesign work, would further like this contextual info not mapped separately, but available
based on the result set being processed.