There are several factors that might influence the speed of a query. Maybe there should be a possibility to split a complex predicate to test for this, the splitting can go as far as one query per node. The bounds for the size of the XT are set by considering Intermediate bags There should be as few intermediate bags as possible, especially if they have a large content. Memory Objectivity allocates for each thread a certain amount of memory when it initializes and it allocates a handle. There is an upper bound for the number of handles.
Cost There is an object indicating the cost to retrieve objects from a Domain.
This information is be calculated from the constructed Execution Tree and the Query Tree it was constructed from.