# Question: The indexed nested loop join algorithm described in Section 13 5

The indexed nested-loop join algorithm described in Section 13.5.3 can be inefficient if the index is a secondary index, and there are multiple tuples with the same value for the join attributes. Why is it inefficient? Describe a way, using sorting, to reduce the cost of retrieving tuples of the inner relation. Underwhat conditions would this algorithm be more efficient than hybrid merge–join?

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