Suppose you need to sort relation r using sort-merge and merge—join the result with an already sorted relation s.

a. Describe how the sort operator is broken into sub operators to model the pipelining in this case.

b. The same idea is applicable even if both inputs to the merge join are the outputs of the sort—merge-operations. However, the available memory has to be shared between the two merge operations (the merge—join algorithm itself needs very little memory). What is the effect of having to share a memory on the cost of each sort-merge operation?