
SUBJECT: enable selection push-down through adjustment.
  Selection push-down has been disabled through adjustment, since predicates
  on timestamps are not allowed to be pushed-down as they are modified.
  TASK: allow selection push-down of all predicates that do not involve 
        timestamps, and of all conjuctive predicates of predicates timestamps
        involving timestamps.

SUBJECT: create an execution path of adjustment with no sort on (A,T).
  In order to have joined-tuples derived from the same (left) input tuple 
  consecutive and splitting points respectively alignment intervals consecutive
  the joint result is sorted by (A,T) first. This could be avoided since the  
  left relation in a left outer join is always used as the outer relation and 
  postgres does not support block-joins. Thus in this case joined tuples form 
  the same left tuples are already consecutive and only splitting points 
  respectively alignment intervals should be sorted in main memory.
  TASK: create a new execution path for this when enough memory is available for   
        main memory sort. The sort would only involve time points respectively 
        timestamps and the memory usage should be small even for large 
        relations.        

