Join Strategies

1. We've seen how to estimate the size of a join. Now we look at estimating the cost of processing a join.
2. Several factors influence the selection of an optimal strategy:
   • Physical order of tuples in a relation.
   • Presence of indices and type of index (clustering or not).
   • Cost of computing a temporary index for the sole purpose of processing one query.
3. We'll look at computing the expression deposit customer assuming no indices exist. We also let

       (number of deposit tuples)
   
      (number of customer tuples)
   
   

• Simple Iteration
• Block-Oriented Iteration
• Merge-Join
• Use of an Index
• Hash Join
• Three-Way Join