Manage Serialization Conflicts in High Isolation

Handling Serialization Errors in SERIALIZABLE Mode

Write a PostgreSQL query to simulate a transaction that may encounter a serialization error under SERIALIZABLE isolation.

Solution:

-- Begin a transaction with SERIALIZABLE isolation.
BEGIN;
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;

-- Attempt to update an account balance.
UPDATE Accounts
SET balance = balance - 50
WHERE account_id = 1;

-- (Simulate potential conflict with a concurrent transaction.)

-- Commit the transaction.
COMMIT;

Explanation:

• Purpose of the Query:
• The goal is to show how a transaction running in SERIALIZABLE mode is susceptible to serialization errors if conflicts occur.
• This demonstrates the strict ordering enforced by the SERIALIZABLE isolation level.
• Key Components:
• SET TRANSACTION ISOLATION LEVEL SERIALIZABLE; : Sets the strictest isolation.
• The UPDATE statement performs a critical operation that may conflict with others.
• Real-World Application:
• Used in environments where absolute consistency is required, and conflicts must be detected to prevent anomalies.

Notes:

• If a serialization conflict is detected, PostgreSQL will raise an error and the transaction must be retried.
• Applications must handle such errors gracefully, typically via retry logic.

For more Practice: Solve these Related Problems:

• Write a PostgreSQL query to begin a transaction with SERIALIZABLE isolation, update a critical record in the Accounts table, and simulate a serialization conflict.
• Write a PostgreSQL query to start a transaction with SERIALIZABLE isolation, insert a new record in the Orders table, and then manually trigger a rollback to simulate a serialization error.
• Write a PostgreSQL query to update multiple rows in the Reservations table under SERIALIZABLE isolation, expecting a serialization conflict, then commit.
• Write a PostgreSQL query to perform an update on the Inventory table under SERIALIZABLE isolation and observe how the system handles concurrent updates.

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