代写B+ tree、R代写代做、代做deadline留学生、R编程语言调试

日期：2019-04-23 10:49

Assignment 3

Please make sure that you always use notations consistent with lecture notes.

Different notations will not be accepted. The deadline for assignment 3 is:

Mon 29 Apr, 10:00 am

Question 1 (8 marks)

Consider the B+ tree shown in the following as an original tree.

Answer the following questions:

1) (2 marks) There are currently 18 records in this tree. How many additional records could

be added to this tree without changing its height (give the maximum possible number)?

2) (3 marks) Show the B+ tree after inserting a data entry with key 3 into the original tree.

3) (3 marks) Show the B+ tree after deleting the data entry with key 91 from the original

tree.

Question 2 (4 marks)

Consider a relation R(a,b,c,d,e,f,g,h) containing 10,000,000 records, where each data page of

the relation holds 10 records. R is organised as a sorted file with the search key R.a. Assume

that R.a is a candidate key of R, with values lying in the range 0 to 9,999,999. For the

relational algebra , state which of the following

approaches (or combination thereof) is the most likely to be the cheapest:

1. Access the sorted file for R directly.

2. Use a clustered B+ tree index on attribute R.a.

3. Use a clustered B+ tree index on attribute R.b.

4. Use a linear hashed index on attribute R.a.

5. Use a clustered B+ tree index on attributes (R.a, R.b).

6. Use a linear hashed index on attribute s (R.a, R.b).

We assume that the database considers index-only plans. Index-only plans allow an index to

contain all columns required to answer the query. It means that by using index-only plans,

you will not have to access the data records in the file that contain the queried relations.

π{a,b}(σ(a>2,000,000 and a<8,000,000)

(R))

Question 3 (8 marks)

Consider the schedule below. Here, R(*) and W(*) stand for ‘Read’ and ‘Write’, respectively.

, , and represent four transactions and represents a time slot.

Each transaction begins at the time slot of its first Read, and commits right after its last Write

(same time slot).

Regarding the following questions, give and justify your answers.

1) Assume a checkpoint is made between and , what should be done to the four

transactions when the crash happens between and . (2 marks)

2) Is the transaction schedule conflict serialisable? Give the precedence graph to justify your

answer. (2 marks)

3) Construct a schedule (which is different from above) of these four transactions which

causes deadlock when using two-phase locking protocol. If no such schedule exists,

explain why. (2 marks)

4) Construct a schedule (which is different from above) of these four transactions which

does not cause deadlock when using two-phase locking protocol. If no such schedule

exists, explain why. (2 marks)

T1 T2 T3 T4 ti

Time

R(B) R(A) W(B) W(A)

R(A) W(A)

R(B) W(B)

R(A) W(A) R(B) W(B)

t7 t8

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