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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)) < size(s(S)), the join will have fewer number of disk block accesses if
  • a)
    relation r(R) is in the outer loop.
  • b)
    relation s(S) is in the outer loop.
  • c)
    join selection factor between r(R) and s(S) is more than 0.5.
  • d)
    join selection factor between r(R) and s(S) is less than 0.5.
Correct answer is option 'A'. Can you explain this answer?
Verified Answer
Consider a join (relation algebra) between relations r(R)and s(S) usin...
Nested loop join is one of the methods to implement database in memory. A nested loop join is an  algorithm that joins two sets by using two nested loops.
According to nested join,given relation R and S For each tuple r in R do For each tuple s in S do If r and s satisfy the join condition Then output the tuple <r,s> Cost estimations for the above loop: – b(R) and  b(S) number of blocks in R and in S – Each block of outer relation is read once – Inner relation is read once for each block of outer relation Summing up : IO= b(R)+n(R)*b(S) total  IO operations Lets assume |R|>|S|  i.e b(R) =10 , n(R) = 100 , n(S)= 30 ,and b(s) =3 Now,   if R is outer relation then, IO= 10+100*3=340 if S is outer relation then IO=3+30*10=303 As it can be observed , that total IO is lesser if the value of outer variable is less and as it is already given that |R|<|S|.Therefore,  Relation r(R) should be in the outer loop to have fewer number of disk block accesses.
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Consider a join (relation algebra) between relations r(R)and s(S) usin...
And size(s(S)) are given and are larger than the buffer size, the algorithm for the nested loop join would be as follows:

1. Read the first block of relation r(R) into the first buffer.
2. For each block b of relation s(S), do the following:
a. Read block b into the second buffer.
b. For each tuple t1 in the first buffer, do the following:
i. For each tuple t2 in the second buffer, do the following:
- Join tuples t1 and t2 and add the result to the third buffer.
3. Write the contents of the third buffer to disk.

This algorithm continues until all blocks of relation s(S) have been processed. The nested loop join is a simple but inefficient join algorithm, especially if the size of relation r(R) or s(S) is large. It has a time complexity of O(n^2), where n is the number of tuples in relation r(R) multiplied by the number of tuples in relation s(S).
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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)) < size(s(S)), the join will have fewer number of disk block accesses ifa)relation r(R) is in the outer loop.b)relation s(S) is in the outer loop.c)join selection factor between r(R) and s(S) is more than 0.5.d)join selection factor between r(R) and s(S) is less than 0.5.Correct answer is option 'A'. Can you explain this answer?
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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)) < size(s(S)), the join will have fewer number of disk block accesses ifa)relation r(R) is in the outer loop.b)relation s(S) is in the outer loop.c)join selection factor between r(R) and s(S) is more than 0.5.d)join selection factor between r(R) and s(S) is less than 0.5.Correct answer is option 'A'. Can you explain this answer? for Computer Science Engineering (CSE) 2024 is part of Computer Science Engineering (CSE) preparation. The Question and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus. Information about 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 ifa)relation r(R) is in the outer loop.b)relation s(S) is in the outer loop.c)join selection factor between r(R) and s(S) is more than 0.5.d)join selection factor between r(R) and s(S) is less than 0.5.Correct answer is option 'A'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for 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 ifa)relation r(R) is in the outer loop.b)relation s(S) is in the outer loop.c)join selection factor between r(R) and s(S) is more than 0.5.d)join selection factor between r(R) and s(S) is less than 0.5.Correct answer is option 'A'. Can you explain this answer?.
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