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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?
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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)+b(R)*b(S) total IO operations Lets assume |R|>|S| i.e b(R) =10 and b(s) =3 Now, if R is outer relation then, IO= 10+10*3=40 if S is outer relation then IO=3+10*3=33 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...
The Nested Loop Join Algorithm
The nested loop join is a simple join algorithm that uses two nested loops to compare each tuple in one relation with each tuple in the other relation. It is commonly used when one of the relations is small enough to fit in memory.
The algorithm works as follows:
1. Read a block of tuples from relation R into a buffer.
2. For each tuple in the buffer, read a block of tuples from relation S into another buffer.
3. Compare each tuple in the R-buffer with each tuple in the S-buffer.
4. If a match is found, output the joined tuples.
5. Repeat steps 2-4 until all tuples in relation R have been processed.
Number of Disk Block Accesses
The number of disk block accesses required by the nested loop join algorithm depends on the order in which the relations are accessed in the nested loops. In this case, there are three buffers available, one of which is reserved for intermediate results.
When relation R is in the outer loop (option A), the algorithm works as follows:
- Read a block of tuples from relation R into the R-buffer.
- For each tuple in the R-buffer, read a block of tuples from relation S into the S-buffer.
- Compare each tuple in the R-buffer with each tuple in the S-buffer.
- Output the joined tuples and store them in the intermediate buffer.
- Repeat steps 2-4 until all tuples in relation R have been processed.
In this case, each block of tuples from relation R is read only once, and each block of tuples from relation S is read multiple times (once for each block of tuples from relation R). Therefore, the number of disk block accesses is equal to the number of blocks in relation S.
When relation S is in the outer loop (option B), the algorithm works similarly, but each block of tuples from relation S is read only once, and each block of tuples from relation R is read multiple times. Therefore, the number of disk block accesses would be equal to the number of blocks in relation R.
When the join selection factor between relation R and relation S is more than 0.5 (option C), it means that relation R is smaller than relation S. In this case, it is more efficient to have relation R in the outer loop because it requires fewer disk block accesses.
Similarly, when the join selection factor between relation R and relation S is less than 0.5 (option D), it means that relation R is larger than relation S. In this case, it would be more efficient to have relation S in the outer loop.
Therefore, option A is the correct answer because it minimizes the number of disk block accesses by having relation R in the outer loop.
The nested loop join is a simple join algorithm that uses two nested loops to compare each tuple in one relation with each tuple in the other relation. It is commonly used when one of the relations is small enough to fit in memory.
The algorithm works as follows:
1. Read a block of tuples from relation R into a buffer.
2. For each tuple in the buffer, read a block of tuples from relation S into another buffer.
3. Compare each tuple in the R-buffer with each tuple in the S-buffer.
4. If a match is found, output the joined tuples.
5. Repeat steps 2-4 until all tuples in relation R have been processed.
Number of Disk Block Accesses
The number of disk block accesses required by the nested loop join algorithm depends on the order in which the relations are accessed in the nested loops. In this case, there are three buffers available, one of which is reserved for intermediate results.
When relation R is in the outer loop (option A), the algorithm works as follows:
- Read a block of tuples from relation R into the R-buffer.
- For each tuple in the R-buffer, read a block of tuples from relation S into the S-buffer.
- Compare each tuple in the R-buffer with each tuple in the S-buffer.
- Output the joined tuples and store them in the intermediate buffer.
- Repeat steps 2-4 until all tuples in relation R have been processed.
In this case, each block of tuples from relation R is read only once, and each block of tuples from relation S is read multiple times (once for each block of tuples from relation R). Therefore, the number of disk block accesses is equal to the number of blocks in relation S.
When relation S is in the outer loop (option B), the algorithm works similarly, but each block of tuples from relation S is read only once, and each block of tuples from relation R is read multiple times. Therefore, the number of disk block accesses would be equal to the number of blocks in relation R.
When the join selection factor between relation R and relation S is more than 0.5 (option C), it means that relation R is smaller than relation S. In this case, it is more efficient to have relation R in the outer loop because it requires fewer disk block accesses.
Similarly, when the join selection factor between relation R and relation S is less than 0.5 (option D), it means that relation R is larger than relation S. In this case, it would be more efficient to have relation S in the outer loop.
Therefore, option A is the correct answer because it minimizes the number of disk block accesses by having relation R in the outer loop.
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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?.
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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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?, a detailed solution 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? has been provided alongside types of 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? theory, EduRev gives you an
ample number of questions to practice 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? tests, examples and also practice Computer Science Engineering (CSE) tests.
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