Question 1

How does a search of a key value in a B-tree differ from a search in a binary search tree?

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Question 2

What is the maximum number of nodes in a B tree of height 3 and degree 10?

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Question 3

What is the advantage of using a B-tree instead of a 2-3 tree for indexing external data?

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Question 4

Why is random access preferable over sequential access for supporting external tables?

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Question 5

Mergesort requires us to store the entire array of key values in internal memory before we can begin the merge operation.

Accepted Answer

Mergesort can be implemented in a way that it does not require the entire array to be in internal memory for the merge operation, especially in external sorting scenarios where data is read from and written to external storage in chunks.

Question 6

Inserting a single key value into a B-tree can result in more than one node splitting operation.

Accepted Answer

When inserting a key value in a B-tree, if the node into which the key is to be inserted is already full, then a splitting operation is required. This may result in the splitting of multiple nodes, as the newly added key may cause nodes higher up the tree to also become full and require splitting. Therefore, inserting a single key value into a B-tree can result in more than one node splitting operation.

Question 7

If a B-tree of order 5 contains the key values 20,40,50,60,80,90 and 100,and the root contains only the key value 60,then deleting the key 20 will require us to merge the two child nodes.

Accepted Answer

In a B-tree of order 5, each node can have a minimum of 2 keys and a maximum of 4 keys. Deleting the key 20 from a child node that already has the minimum number of keys (2 keys in this case) would indeed require adjustments. However, without knowing the exact distribution of the keys across the nodes, we cannot definitively say that it will require merging the two child nodes. It's possible that a redistribution of keys among siblings or borrowing a key from an adjacent sibling could suffice, depending on the tree's structure.

Question 8

External mergesort begins by merging sorted runs.

Accepted Answer

External mergesort begins by dividing the data into smaller chunks or runs, sorting each run in memory, and then merging those sorted runs.

Question 9

When we perform external hashing,we hash the data file instead of the index file.

Accepted Answer

In external hashing, it is the index file that is hashed, not the data file. This technique is used to manage disk-based data structures efficiently.

Question 10

Name two advantages to storing a data structure in external storage.

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Quiz 15: External Methods