Raghuramkrishnan

Question

Tl:R(X), T1:R(Y), T1:W(X), T2:R(Y), T3:W(Y), Tl:W(X), T2:R(Y)

is this schedule view serializable?

Comments

Nope.Polygraph have cycle.

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can u show the polygraph?

Answer 1

For View Equivalence:

1. If transaction Ti reads initial value of any data item X in one schedule it must do the same in all the equivalent schedules
2. If transaction Ti writes the final value of any data item X in one schedule, it must do the same in all the view-equivalent schedules. 
3. If transaction Ti reads data item X written by transaction Tj, it must do the same in all the view equivalent schedules

Comments

@Gurdeep Saini

T1 T3 T2 is view Serial schedule? Right or Wrong?

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This is view serializable.

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@Lakshman Patel RJIT

your polygraph is wrong

because it does not contain T2 to T3

yes final write by T3 on Y but there is no write on Y in T2 

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@Ashishwastaken yes T1 T3 T2 is view Serial schedule

Answer 2

It is not view serializable as t2 can't come after t3 and vise versa