3. The method of claim 2 , wherein determining the cost associated with merging further comprises determining an optimized query cost resulting from an optimized query generated by merging any two singleton clusters.
3. The method of claim 2 , wherein determining the cost associated with merging further comprises determining an optimized query cost resulting from an optimized query generated by merging any two singleton clusters. 4. The method of claim 3 , wherein merging only singleton clusters where the cost associated with merging indicates that merging is cost effective further comprises: obtaining a cost of performing queries for each individual singleton cluster; and comparing the cost of performing queries for each individual singleton cluster with the optimized query cost.