Query instance comparisons

[MerrionComputing]

With the event stream backed queries storing the bits that make up the query result it is theoretically possible to compare two runs of a given query and see what underlying components of the result have changed.

For example you could find projections that are added or removed since the last run (i.e. the set fulfilling the equivalent of an SQL WHERE condition has changed) and also the projection sequence number of the projections underlying the query.