Consider again the schema with the Sailors relation: Sailors(sid: integer, sname: string, rating: integer, age: real) Assume
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Sailors(sid: integer, sname: string, rating: integer, age: real)
Assume that each tuple of Sailors is 50 bytes long, that a page can hold 80 Sailors tuples, and that we have 500 pages of such tuples. For each of the following selection conditions, estimate the number of pages retrieved, given the catalog information in the question.
1. Assume that we have a B+-tree index T on the search key Sailors.sid , and assume that IHeight(T) = 4, INPages(T ) = 50, Low(T ) = 1, and High(T ) = 100,000.
(a) σSailors.sid<50,000(Sailors)
(b) σSailors.sid=50,000(Sailors)
2. Assume that we have a hash index T on the search key Sailors.sid , and assume that IHeight(T) = 2, INPages(T ) = 50, Low(T ) = 1, and High(T ) = 100,000.
(a) σSailors.sid<50,000(Sailors)
(b) σSailors.sid=50,000(Sailors)
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Related Book For
Database management systems
ISBN: 978-0072465631
3rd edition
Authors: Raghu Ramakrishan, Johannes Gehrke, Scott Selikoff
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