GATE CSE 2007 | GATE CSE Year Wise Previous Years Questions

GATE CSE 2007

MCQ (Single Correct Answer)

-0.6

Consider the following two transactions: T₁ and T₂.

T₁: read (A);                  T₂: read (B);
    read (B);                      read (A);
    if A = 0 then B ← B + 1;       if B ≠ 0 then A ← A - 1;
    write (B);                     write (A);

Which of the following schemes, using shared and exclusive locks, satisfy the requirements for strict two phase locking for the above transactions?

S1 : lockS(A); 	        S2 : lockS(B);
     read (A);               read (B);
     lockS(B);               lockS(A);
     read (B);               read (A);
     if A = 0                if B ≠ 0
     then B ← B + 1;        then A ← A - 1;
     write (B);              write (A);
     commit;                 commit;
     unlock (A);             unlock (B);
     unlock (B);             unlock (A);

S1 : lockX(A);          S2 : lockX(B);
     read (A);               read (B);
     lockX(B);               lockX(A);
     read (B);               read (A);
     if A = 0                if B ≠ 0
     then B ← B + 1;        then A ← A - 1;
     write (B);              write (A);
     unlock (A);             unlock (A);
     commit;                 commit;
     unlock (B);             unlock (A);

S1 : lockS(A);           S2 : lockS(B);
     read (A);                read (B);
     lockX(B);                lockX(A);
     read (B);                read (A);
     if A = 0                 if B ≠ 0
     then B ← B + 1;         then A ← A - 1;
     write (B);               write (A);
     unlock (A);              unlock (B);
     commit;                  commit;
     unlock (B);              unlock (A);

S1 : lockS(A);           S2 : lockS(B);
     read (A);                read (B);
     lockX(B);                lockX(A);
     read (B);                read (A);
     if A = 0                 if B ≠ 0
    then B ← B + 1;        then A ← A - 1;
     write (B);               write (A);                                                                                                     
     unlock (A);              unlock (A);
     unlock (B);              unlock (B);
     commit;                  commit;

GATE CSE 2007

MCQ (Single Correct Answer)

-0.6

Consider the following schedules involving two transactions. Which one of the following statements is TRUE?

S₁: r₁(X); r₁(Y); r₂(Y); r₂(X); w₂(Y); w₁(X);

S₂: r₁(X); r₂(X); r₂(Y); w₂(Y); r₁(Y); w₁(X);

Both S₁ and S₂ are conflict serializable.

S₁ is conflict serializable and S₂ is not conflict serializable.

S₁ is not conflict serializable and S₂ is conflict serializable.

Both S₁ and S₂ are not conflict serializable.

GATE CSE 2007

MCQ (Single Correct Answer)

-0.6

Consider the following relation schemas :

b-Schema = (b-name, b-city, assets)
a-Schema = (a-num, b-name, bal)
d-Schema = (c-name, a-number)

Let branch, account and depositor be respectively instances of the above schemas. Assume that account and depositor relations are much bigger than the branch relation.

Consider the following query:
П_c-name (σ_{b-city = “Agra” ⋀ bal < 0} (branch $$ \Join $$ (account $$ \Join $$ depositor))

Which one of the following queries is the most efficient version of the above query ?

П_c-name (σ_{bal < 0} (σ_{b-city = “Agra”} branch $$ \Join $$ account) $$ \Join $$ depositor)

П_c-name (σ_{b-city = “Agra”}branch $$ \Join $$ (σ_{bal < 0} account $$ \Join $$ depositor))

П_c-name (σ_{b-city = “Agra”}branch $$ \Join $$ σ_{b-city = “Agra” ⋀ bal < 0} account) $$ \Join $$ depositor)

П_c-name (σ_{b-city = “Agra” ⋀ bal < 0} account $$ \Join $$ depositor))

GATE CSE 2007

MCQ (Single Correct Answer)

-0.6

Consider the relation employee(name, sex, supervisorName) with name as the key, supervisorName gives the name of the supervisor of the employee under consideration. What does the following Tuple Relational Calculus query produce?

$$\eqalign{ & \{ e.name\,|\,employee(e) \wedge \cr & (\forall x)[\neg employee(x) \vee \cr & x.\sup ervisorName \ne e.name\, \vee \cr & x.sex = 'male']\} \cr} $$

Names of employees with a male supervisor.

Names of employees with no immediate male subordinates.

Names of employees with no immediate female subordinates.

Names of employees with a female supervisor.

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