Question

Assume that you have built a B tree index on a file containing 50,000 records. The key field for this B tree index is a 40 bytes string. Pointers (both block and record pointers) are 10 bytes. The size of one block is 1,024 bytes. Then there are ________ number level in the tree. (Assume that root is level 0)

Answer 1

option (b)

The order of B- Tree is:
$n\ast 10-(n-1{)}^{\ast }(40-10)<=102460n<=974n<=16$

Root has 16 pointers and 15 records.
Level 1 has 256 pointers and 240 records.
Level 2 has 4096 pointers and 3840 records.
Level 3 has 65536 pointers and 61440 records > 50000 records.

Therefore 3 levels are needed.