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Consider a join (relation algebra) between relations r(R)and s(S) using the nested loop method. There are 3 buffers each of size equal to disk block size, out of which one buffer is reserved for intermediate results. Assuming  size(r(R))

Consider a join (relation algebra) between relations r(R)and s(S) using the nested loop method. There are 3 buffers each of size equal to disk block size, out of which one buffer is reserved for intermediate results. Assuming  size(r(R))<size(s(S)), the join will have fewer number of disk block accesses if Correct Answer relation r(R) is in the outer loop.

Concept:

Nested loop join algorithm:

No of block transfers = nr x bs + br

Where nr is number of tuples in relation R and bs and br are the number of blocks in relation R and S respectively.

Explanation :

In question it is given that size(r(R))<size(s(S)) this means  bs > br and nr < ns .

Example :

Suppose relation r is in the outer loop:

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Suppose relation s is in the outer loop:

Block transfer = 100 x 10 + 20 = 1020

So relation r should be in the outer loop for effective nested loop join algorithm.

Hence option 1 is the correct answer.

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