Figure 7

Simplified heavy-atom contacts query. The size of the join is reduced by applying two right associative join clauses, shown in bold. Right associative joins are a mechanism to control the order of join evaluation. In this case we insure that only the rows meeting satisfying the given predicates participate in the final self-join (i.e. heavy-atoms and only the first 1 ns of simulation time). The spatial-index join is shown in bold-italics. This clause allows SQL to trim away most atoms outside the cutoff range without needing to perform the distance calculation, greatly reducing the number of operations as well as rows that would later be thrown away by the distance cutoff. Finally, MERGE joins are explicitly specified to avoid the optimizer choosing a HASH join for the coordinate table self-join.