What is the expected result if a transaction running at Serializable isolation level reads data that another concurrent transaction later modifies and commits?

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PostgreSQL - Transactions and Concurrency

What is the expected result if a transaction running at Serializable isolation level reads data that another concurrent transaction later modifies and commits?

AThe first transaction sees the original data and may abort if conflicts occur

BThe first transaction immediately sees the new data

CThe first transaction blocks until the other commits

DThe first transaction ignores the other transaction's changes permanently

Step-by-Step Solution

Solution:

Step 1: Understand Snapshot Behavior in Serializable
Serializable transactions see a consistent snapshot; they do not see changes made after their start.
Step 2: Consider Conflict Detection
If the other transaction's commit conflicts with the first, the first may abort to maintain serializability.
Final Answer:
The first transaction sees the original data and may abort if conflicts occur -> Option A
Quick Check:
Serializable snapshot = Original data, possible abort [OK]

Quick Trick: Serializable reads original snapshot; conflicts cause aborts [OK]

Common Mistakes:

Assuming immediate visibility of changes
Thinking transactions block on reads
Believing changes are ignored forever

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What is the expected result if a transaction running at Serializable isolation level reads data that another concurrent transaction later modifies and commits?

Step 1: Understand Snapshot Behavior in Serializable

Step 2: Consider Conflict Detection

Final Answer:

Quick Check:

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