
206
■
Distributed Database Systems
Step 2: Apply reduction technique to q, which will produce a list of monorelation subqueries and
a sequence of irreducible subqueries q1 → q2 →. . .→ qn.
Step 3: Ignore all monorelation subqueries (since they are already processed by OVQPs at local
sites).
Step 4: for I 1 to n, repeat Step5 to Step8 [n is the total number of irreducible subqueries].
Step 5: Choose the irreducible subquery qi involving the smallest fragments.
Step 6: Determine the best strategy, pairs of (F, S ), for qi. [F represents a fragment and S represents
the processing sites.]
Step 7: For each pair (F, S), transfer the fragment ...