题目
题目

INFO20003_2025_SM2 Exam: Database Systems (INFO20003_2025_SM2)- Requires Respondus LockDown Browser

匹配题

Query Optimisation Plan 2  Compute the following results for the below Plan 2:  The result size of the selection on vendor in pages (marked as 'A' in the diagram) The result size of the child join in pages (marked as 'B' in the diagram) The cost of the selection on vendor in I/Os (note this also accounts for the index access cost as well) (marked as 'C' in the diagram) The cost of the child join in I/Os (marked as 'D' in the diagram) The cost of the parent join in I/Os (marked as 'E' in the diagram)   Figure 3.3.2: PLAN 2. 1: The result size of the selection on Vendor in PAGES (marked as 'A' in the diagram) 2: The result size of the child join in PAGES (marked as 'B' in the diagram) 3: The cost of the selection on Vendor in I/Os (note this also accounts for the index access cost as well) (marked as 'C' in the diagram) 4: The cost of the child join in I/Os (marked as 'D' in the diagram) 5: The cost of the parent join in I/Os (marked as 'E' in the diagram)

选项
A.500
B.50
C.20,000
D.100
E.105
F.10,000
G.60
H.10,005
I.750
J.5
K.650
L.20,100
M.[Select this if none of the other options are correct]
N.51
O.6
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思路分析
We are given a matching-type question about Plan 2 in a query optimisation exercise. The prompt asks us to compute five results for Plan 2: 1) The result size of the selection on vendor in pages (A) 2) The result size of the child join in pages (B) 3) The cost of the selection on vendor in I/Os (C) 4) The cost of the child join in I/Os (D) 5) The cost of the parent join in I/Os (E) The available answer options include a mix of numeric values and a generic placeholder for “none of the others.” The provided answer mapping indicates the intended selections were: A = 5, B = 100, C = 6, D = 10,005, E = 750. Below I’ll analyze each option in turn, noting why a given choice could be plausible and why alternative options would be incorrect. - Analysis of option choices for A (The result size of the selection on Vendor in PAGES): • If we consider 5 pages as the result size, this implies a relatively small, highly selective vendor selection after applying an index or predicate. This would be plausible if the vendor relation is large but the selection condition reduces it to only a handful of qualifying rows that aggregate to about 5 pages. • Why some other options are less suitable: 500, 20,000, 10,000, 650, and 60 pages would imply much larger intermediate results from the vendor selection, which would typically be unlikely if ......Login to view full explanation

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类似问题

Query Optimisation Plan 1  Compute the following results for the below Plan 1:  The result size of the child join in pages (marked as 'A' in the diagram) The cost of the child join in I/Os (marked as 'B' in the diagram).  The cost of the parent join in I/Os (marked as 'C' in the diagram)     Figure 3.3.1: PLAN 1. 1: The result size of the child join in PAGES (marked as 'A' in the diagram) 2: The cost of the child join in I/Os (marked as 'B' in the diagram) 3: The cost of the parent join in I/Os (marked as 'C' in the diagram)

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