nptel pdf

Question

Q Consider a relation R(a, b, c) ordered on a non-key attribute b, and an index is maintained on attribute c. To evaluate the following expression, which is a better order of operation? σ(b=‘abc’∧c=12)(R)

A. First filter tuples using index on c and then search for b

B. First search tuples for the given value of b and then use index on c

C. The order of operation does not matter

D. Insufficient data to answer

 

Comments

d?

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Yes plz explain

Answer 1

Answer is D) Insufficient to answer

The size of block and file size is not mentioned . If they first search using non-key attribute ‘b’ ,then it require to perform binary search for efficiently fetching.If they first search using index ‘c’ ,then it require to fetch the index entry. But none of them is mentioned. So we cannot figure out the actual block transfers required to fetch index entry or to binary search the record.