Transactions & ACID · SQL SQL
Which of the following phenomena can still occur under the 'Repeatable Read' isolation level in standard ANSI SQL, but is prevented in PostgreSQL's i…
Practice question from Transactions & ACID (SQL SQL), with the correct answer and a step-by-step solution.
hard · MCQ · Q-9D7AF1
Which of the following phenomena can still occur under the 'Repeatable Read' isolation level in standard ANSI SQL, but is prevented in PostgreSQL's implementation?
- A.Dirty Read
- B.Non-Repeatable Read
- C.Phantom ReadCorrect answer
- D.Lost Update
Solution
According to the ANSI SQL standard, Repeatable Read allows phantom reads (where a concurrent transaction inserts new rows matching a range query). However, PostgreSQL's Repeatable Read level uses SSI (Snapshot Isolation), which prevents phantom reads as well.
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