COMP9315 Sample Exam
The University of New South Wales
COMP9315 DBMS Implementation
Sample Exam
DBMS Implementation
[Instructions] [Notes] [PostgreSQL] [C]
[Q1] [Q2] [Q3] [Q4] [Q5] [Q6] [Q7] [Q8]
Question 7 (10 marks)
Consider two relations R(id,x,y) and S(rid,a,b,c), with bR = 100 and bS = 500, and a join operation on these two tables:
select * from R join S on (R.id = S.rid)
Assume that each R tuple joins with exactly one S tuple, and that any hash functions used distribute the tuples uniformly.
Ignoring the cost of writing the final output (the joined tuples), describe how each of the following joins would occur and calculate the number of reads and writes that would occur in evaluating them:
a. using simple hash join with 10 memory buffers
b. using hybrid hash join with 20 memory buffers, and holding one bucket of R in memory
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