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Data Mgmt Lab_Part_33

# Data Mgmt Lab_Part_33 - Tree-Structured Indexing 97 Answer...

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Tree-Structured Indexing 97 Answer 10.8 Answer omitted. Exercise 10.9 The algorithms for insertion and deletion into a B+ tree are presented as recursive algorithms. In the code for insert , for instance, a call is made at the parent of a node N to insert into (the subtree rooted at) node N , and when this call returns, the current node is the parent of N . Thus, we do not maintain any ‘parent pointers’ in nodes of B+ tree. Such pointers are not part of the B+ tree structure for a good reason, as this exercise demonstrates. An alternative approach that uses parent pointers—again, remember that such pointers are not part of the standard B+ tree structure!—in each node appears to be simpler: Search to the appropriate leaf using the search algorithm; then insert the entry and split if necessary, with splits propagated to parents if necessary (using the parent pointers to find the parents). Consider this (unsatisfactory) alternative approach: 1. Suppose that an internal node N is split into nodes N and N 2. What can you say about the parent pointers in the children of the original node N ? 2. Suggest two ways of dealing with the inconsistent parent pointers in the children of node N . 3. For each of these suggestions, identify a potential (major) disadvantage. 4. What conclusions can you draw from this exercise?

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