What are the advantages and disadvantages of hash indices relative to B+-tree indices? How might the type of index available influence the choice of a query processing strategy?
Answer to relevant QuestionsAssume (for simplicity in this exercise) that only one tuple fits in a block and memory holds at most 3 page frames. Show the runs created on each pass of the sort-merge algorithm, when applied to sort the following tuples ...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? ...Consider the relations r1 (A, B, C), r2 (C, D, E), and r3 (E, F) of Exercise. Assume that there are no primary keys, except the entire schema. Let V (C, r1) be 900, V (C, r2) be 1100, V (E, r2) be 50, and V (E, r3) be 100. ...Show that the lowest-cost join order can be computed in time O(3n). Assume that you can store and look up information about a set of relations (such as the optimal join order for the set, and the cost of that join order) in ...Database-system implementers have paid much more attention to the ACID properties than have file-system implementers. Why might this be the case?
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