Databricks Data Engineer Professional Question 13
Select 3A data engineering team is using Delta Lake for a production pipeline where multiple users and jobs concurrently write to the same Delta table. How does Delta Lake's Optimistic Concurrency Control (OCC) ensure isolation in such scenarios, and which types of transactions might conflict?
- A
Delta Lake validates that no two concurrent transactions modify the same data during the commit phase.
- B
Conflicts may occur if two transactions concurrently update different rows of the same Delta table.
- C
Delta Lake uses a version-based check to ensure that reads and writes are consistent with the latest committed table state.
- D
Conflicts may occur if one transaction deletes data while another transaction updates the same data.
- E
Delta Lake uses pessimistic locking to prevent all concurrent writes to the table.
Show answer and explanation
Correct answers: A, C, D
Explanation
Delta Lake's Optimistic Concurrency Control (OCC) ensures isolation by validating during the commit phase that no conflicting changes have been made. Transactions conflict if they modify or delete the same data, but OCC allows non-conflicting concurrent writes to proceed. This design ensures consistency while maximizing parallelism by not requiring pessimistic locking.
- A. Correct.
Delta Lake's OCC ensures isolation by validating during the commit phase that no conflicting writes or deletes have occurred. This is a key mechanism of OCC.
- B. Incorrect.
This is incorrect because Delta Lake allows concurrent updates to different rows in the same table without conflicts, as they do not modify the same data.
- C. Correct.
Delta Lake uses version-based checks to ensure that each transaction's operations are consistent with the latest committed state of the table. This is a part of OCC's design.
- D. Correct.
Conflicts arise when one transaction deletes or modifies data that another transaction is updating or reading. OCC identifies and resolves such conflicts by rejecting one of the conflicting transactions.
- E. Incorrect.
This is incorrect because Delta Lake uses optimistic concurrency control, not pessimistic locking. Pessimistic locking would prevent multiple transactions from writing concurrently, which is not the approach Delta Lake takes.