程序代写代做代考 4 MARKS

4 MARKS
Sample Solutions for Quiz 4, Question 7, Hash Join
Version 1: Student has 350,000 records @ 35 records/page; Teacher has 15,000 records @ 60 records/page. B = 20.
a) [2 marks]
 Errors?
i. Don’t deduct for missing ceilings.
ii. -1 once only for this whole HJ question if they used some other
buffer size besides B = 20
iii. But -0.5 once only if they used 20 partitions instead of B – 1 = 19
 0.5 marks: Student table: ceiling(350,000 rec / 35 rec/page) = 10,000 pages
 0.5 marks: Teacher table: ceiling(15,000 rec / 60 rec/page) = 250 pages
 0.5 marks: Student partition has ceiling(10,000 pages / 19 partitions) =
527 pages/partition.
i. Deduct 0.5 once if they used 20 partitions instead of 19.
 0.5 marks: Teacher partition has ceiling(250 pages / 19 partitions) = 14
pages/partition).
b) [1 mark] iv – neither of the relations needs to be partitioned again
 If they messed up Part (a), then see if the rest of their work would be correct, unless it trivializes the solution.
c) [1 mark] 10,000 + 250 = 10,250 page I/Os
 OK if they assumed the whole HJ @ 3 * (10,000 + 250)
 OK if they said another (10,000 + 250) to write it out (but we don’t
because this is the end of the line)
 Don’t double-deduct for errors that propagate, except in the case of a
trivialized solution.
Version 2: Student has 450,000 records @ 45 records/page; Teacher has 30,000 records @ 60 records/page. B = 25.
a) [2 marks]
 Errors?
i. Don’t deduct for missing ceilings.
ii. -1 once only for this whole HJ question if they used some other
buffer size besides B = 25
iii. But -0.5 once only if they used 25 partitions instead of B – 1 = 24
 0.5 marks: Student table: ceiling(450,000 rec / 45 rec/page) = 10,000 pages
 0.5 marks: Teacher table: ceiling(30,000 rec / 60 rec/page) = 500 pages
1

 0.5 marks: Student partition has ceiling(10,000 pages / 24 partitions) = 417 pages/partition.
 0.5 marks: Teacher partition has ceiling(500 pages / 24 partitions) = 21 pages/partition).
b) [1 mark] iv – neither of the relations needs to be partitioned again
 If they messed up Part (a), then see if the rest of their work would be
correct, unless it trivializes the solution. c) [1 mark] 10,000 + 500 = 10,500 page I/Os
 OK if they assumed the whole HJ @ 3 * (10,000 + 500)
 OK if they said another (10,000 + 500) to write it out (but we don’t
because this is the end of the line)
 Don’t double-deduct for errors that propagate, except in the case of a
trivialized solution.
Version 3: Student has 750,000 records @ 75 records/page; Teacher has 40,000 records @ 80 records/page. B = 35.
a) [2 marks]
 Errors:
i. Don’t deduct for missing ceilings.
ii. -1 once only for this whole HJ question if they used some other
buffer size besides B = 35
iii. But -0.5 once only if they used 35 partitions instead of B – 1 = 34
 0.5 marks: Student table: ceiling(750,000 rec / 75 rec/page) = 10,000 pages
 0.5 marks: Teacher table: ceiling(40,000 rec / 80 rec/page) = 500 pages
 0.5 marks: Student partition has ceiling(10,000 pages / 34 partitions) =
295 pages/partition.
 0.5 marks: Teacher partition has ceiling(500 pages / 34 partitions) = 15
pages/partition).
b) [1 mark] iv – neither of the relations needs to be partitioned again
 If they messed up (a), then see if the rest of their work would be correct, unless it trivializes the solution.
c) [1 mark] 10,000 + 500 = 10,500 page I/Os
 OK if they assumed the whole HJ @ 3 * (10,000 + 500)
 OK if they said another (10,000 + 500) to write it out (but we don’t
because this is the end of the line)
 Don’t double-deduct for errors that propagate, except in the case of a
trivialized solution.
2