VIEW SERIALIZABILITY: Concept & Example (DBMS)

[@CellerCity]

This cleared my doubts. Even the comment section is very informative. Thank you for your efforts.

[@abhi1998able]

Great Tutorial! Solved most of the doubts I had ! Thanks a lot !

[@ritukapurclasses1591]

Your Welcome..Really happy to help

[@ashaynayak5259]

Good job Ritu. It gives very good clarity.

[@ritukapurclasses1591]

Thank you 😊

[@__Sudhaa__]

Why only this vdo got 54k views ... this vdo deserves atleast 1 million+

[@ritukapurclasses1591]

Thank you so much! Please do share with more people.

[@sirpasricharan4986]

finally my view serialization problem solved.....beautiful voice......love u mam

[@ritukapurclasses1591]

+sirpa sricharan thnku dear :) Glad to help you ...

[@shivasai5181]

Nice explanation mam

[@ritukapurclasses1591]

Thank you 🙂

[@abhicomic]

What about conflict pairs w2b and w3b W2a and r3a...? Why aren't these pairs not included in graph

[@ritukapurclasses1591]

As we detected a cycle, we can stop there and then. We don't need to check further...

[@FilminTamil]

mam by how we confrim it is view serializability?

[@ritukapurclasses1591]

If you obtain a serial order by complying 3 conditions: initial read, final update, and read-write sequence, it is view serializable. I have made a lot of videos on such questions.

[@FilminTamil]

@@ritukapurclasses1591 mam another doubt , how we can find number of view equivalence serializable schedule?

[@ritukapurclasses1591]

Find out the number of ways you can create serial schedules without violating the 3 conditions mentioned by me previously.

[@FilminTamil]

@@ritukapurclasses1591 can you please suggest me a video mam

[@ritukapurclasses1591]

I have not made any specific video for this. But the same idea was asked as "conflict equivalent" in Gate 2020 qsn: kzbin.info/www/bejne/kH68ZYmnesqmoLc. So, you can follow the same strategy of swapping terms as shown in this video and also incorporate the flexibility of initial read and final update to obtain view serializable schedules.

[@Steve-nd2wj]

Why is T3 supposedly the last Ti and not T2? This refers to the Final Update where "A" has T2, and "B" has T3.

[@ritukapurclasses1591]

+Steve Hello Steve.. This is because, if you analyse the entries corresponding to data item B i.e. column B, you will get to know that T2 is performing an initial read on B (i.e. reading the value of B from the database) and T3 performs a final update. So, if I put T2 after T3, the initial read will be violated. Recall: All the transactions performing an initial read need to be before the ones performing an update or a final update. Please let me know if any further clarification is required. Happy Learning!!!!

[@Steve-nd2wj]

Ritu Kapur Classes Hi, Thank you for replying back. So hypothetically speaking, if there was an initial read for "A", would it change for the order??

[@ritukapurclasses1591]

Dear Student, First of all, I would say it's a very nice question. Now, the answer to this is, Yes, it will definitely affect the order of transactions. Let me take an example for the same. Say, if T3 performs an initial read on data item A. Then the column of A will become something like this: A Initial Read T3 Final Update T2 Update T2 Therefore, the order in accordance to data item A will be: T3->T2 which is in conflict with the order given by data item B i.e. T2->T1->T3 (as it says T3 will come after T2) Hence, this will make the schedule non-serialization, as there is no feasible serial order of the transaction.

[@SamyakJain1004]

Hey, can you post one more example of view serializability? but the question should be in table format as it easy to refer!

[@ritukapurclasses1591]

+Samyak Jain I have posted the required video. Hope you got what you were looking for. Please let me know in case any other specific topic video is required... Thanks...

[@SamyakJain1004]

Yes Thank you!

[@ritukapurclasses1591]

Glad to help you :)

[@Swansylinks]

Thank you

[@ritukapurclasses1591]

You're welcome

[@nikitachandiramani8140]

If it is forming a cycle.. It should be cyclic right?? Why have u termed it as acyclic??

[@ritukapurclasses1591]

For a schedule to be conflict serializable the precedence graph should be acyclic and not cyclic. But a schedule which is not conflict serializable could be still view serializable if all its conditions are satisfied.

[@lukemoorhouse-bh5vs]

@@ritukapurclasses1591 Yes, but if it goes from T1 to T2 and then T2 to T1 is that not cyclic as a loop is being formed? I feel like this video contradicts your other videos when "Acyclic" has arrows all pointing to nodes that don't form a cycle (loop) and this one seems to form a loop and you term it Acyclic? please confirm.

[@sumitgoyal385]

hi di are u sure its read write sequence ., not write read

[@ritukapurclasses1591]

Hello Sumit. By Read Write Sequence I meant the corresponding order of Read - Write Pairs in both the transaction should remain the same. So it holds for both the cases, Read-Write or Write- Read... For example: T1 T2 W(A) R(B) R(B) R(A) Now no matter whichever tye of swapping I do, T1 should be able to perform W(A) before R(A) of T2. Thus the order is maintained... (I can be called a WR pair too as a WR is just a pair in which a write is performed before a read). Hope I was ale to clarify your doubt...

[@sumitgoyal385]

thnku

[@ritukapurclasses1591]

Sure I'll post a solution to such problems very soon...

[@Sairam30722]

Why R2(B) W3(B) not done

[@ritukapurclasses1591]

As we detected a cycle, we can stop there and then. We don't need to check further...

[@Sairam30722]

@@ritukapurclasses1591 tq you mam I understand fluently in KZbin in this channel only. please upload other engineering videos.

[@ritukapurclasses1591]

@@Sairam30722 Thank you so much... Means a lot...

[@kalyanirani2942]

Not understanding what u r saying

[@ritukapurclasses1591]

Why so? Start with the introductory videos of this concept

[@KULDEEPSINGH-rh3go]

1. Can we say like this "Schedule S is Serializable S is view Serializable to some serial schedule" Also one more doubt : 2. If a schedule 'S' is not View Serializable then 'S' is Non - Serializable Schedule. Is this statement true ? 3. Meaning, will there be any Schedule 'S' which is Serializable but not View Serializable. So confused....... please reply or I'll kill myself.😖😖😖

[@ritukapurclasses1591]

+KULDEEP SINGH 1 and 2 are true... You may please view my videos on Serializability... I have given a hierarchy diagram on serializability check... Let me try to explain it a bit... Step 1) we check if schedule is conflict serializable or not... Step 2) If ans of step 1 is yes we declare the schedule as serializable. If it is no, we say the schedule may or may not be serializable. Step 3) If ans at step 1 was no,we try for view serializability. If we get a view serializable schedule, we say that the input schedule was serializable otherwise it is declared as non-serializable. Clearly, if a schedule's view serializable check fails it can never be Serializable in any possibility...

[@KULDEEPSINGH-rh3go]

one of my faculty from IISc teaches me that there may be a Schedule 'S 'possible which can be Serializable but not view Serializable which violets the statement 1. as well as 2. Moreover, no book has directly written that if a Schedule Serializability is not detected by View Serializability test (Meaning View serializability fails) then we can not directly say that the Schedule is Non-serializable, it could be Serializable. and if you do not agree then provide some source that exactly says this statement that I'm discussing. he also explained to me that View Serializability test is not the final test for a schedule to decide whether a schedule is serializable or not. that makes View Serializability test NP-complete problem. Now I'm just looking for at least one example that is not view serializable but serializable. and by the way ......Thanks for reply...........

[@ritukapurclasses1591]

+KULDEEP SINGH I'll surely get back to you on this...

[@ritukapurclasses1591]

+KULDEEP SINGH yes I confirmed from my faculty of IIT. He says that if a test fails for view serializability, we say it is not view serializble bt cant cmmnt on serializability. This is becoz of huge research going on and he also states that it is a problem which is NP complete. But I need to discuss its proof yet.

[@rohitbale15]

Thanks Kuldeep singh for raising this question. This chat had clarified my concept on serializability