# Sort Merge Join Sort Phase Produces Following Sorted R S Number K Represents Disk Page Con Q35457278

In the sort-merge join, the sort phase produces the followingsorted R and S, where each number k represents a disk pagecontaining records with the join attribute =k

The answer is provided on the bottom but im having ahard time understanding the answer. (Maybe a visual would benice)

Why are smaller values being put into a 2 page bufferand larger values in 1 page buffer? How does that ensure that eachpage is read just once?

Please explain the solution, thank you

Question 1 (10 marks). In the sort-merge join, the sort phase produces the following sorted R and S, where each number k represents a disk page containing records with the join attribute k: S: 1,2,2, 5, 5,5,6,7,7,8,9,10 R: 1,2, 5, 5, 6,6,7,7,7, 8, 8, 8, 8, 10 The memory has B-4 pages. Design a merging phase to produce the join result by reading each page in the sorted S and R exactly once. Discuss how you allocate the 4- page memory to read these pages and output the result. You can use Rk and Sk to denote the pages for the join attribute k in R and S, respectively, and the numbers of pages in Rk and Sk are known. For example, S5 has 3 pages and R5 has 2 pages. Answer: For each k value, the smaller of Rk and Sk is no more than 2, so can be held in a 2-page buffer, and we can use 1-page buffer to read the larger of Rk and Sk, and the remaining 1-page for the output buffer. Since the smaller of Rk and Sk is entirely in the memory, the larger ofRk and Sk will be read only once. Show transcribed image text Question 1 (10 marks). In the sort-merge join, the sort phase produces the following sorted R and S, where each number k represents a disk page containing records with the join attribute k: S: 1,2,2, 5, 5,5,6,7,7,8,9,10 R: 1,2, 5, 5, 6,6,7,7,7, 8, 8, 8, 8, 10 The memory has B-4 pages. Design a merging phase to produce the join result by reading each page in the sorted S and R exactly once. Discuss how you allocate the 4- page memory to read these pages and output the result. You can use Rk and Sk to denote the pages for the join attribute k in R and S, respectively, and the numbers of pages in Rk and Sk are known. For example, S5 has 3 pages and R5 has 2 pages. Answer: For each k value, the smaller of Rk and Sk is no more than 2, so can be held in a 2-page buffer, and we can use 1-page buffer to read the larger of Rk and Sk, and the remaining 1-page for the output buffer. Since the smaller of Rk and Sk is entirely in the memory, the larger ofRk and Sk will be read only once.