Applying OLAP Pre-Aggregation Techniques to ... - Jacobs University

5.5 Experimental Results 93
root node of the lattice was 12.5% of the size of the original dataset. Fig. 5.10 shows
the average query cost as storage space is increased. A small amount of storage space
dramatically reduces the average query cost. The improvement in average query cost
decreases, however, as allocated space goes beyond 36%. Fig. 5.11 shows the scaling
operations selected for pre-aggregation when c = 36%. For this instance of the
storage space constraint, the algorithm selected 49 pre-aggreagates. The total cost of
computing that workload is 6.44e+05. In contrast, computing the workload using the
original dataset incurs a cost of 1.28e + 12.
Figure 5.9. Workload with Uniform Distribution along x, y, and t
Figure 5.10. Average Query Cost over Storage Space