Repeatable Read Isolation

Repeatable Read is a transaction isolation level in database systems that ensures that within a single transaction, all reads of the same data return consistent results, preventing non-repeatable reads. It achieves this by locking rows read by the transaction until the transaction completes, preventing other transactions from modifying those rows. However, it does not prevent phantom reads, where new rows matching a query condition can appear during the transaction.

Also known as: Repeatable Read, Repeatable Read Isolation Level, RR Isolation, Repeatable Read Concurrency Control, MySQL's REPEATABLE-READ

Why learn Repeatable Read Isolation?

Developers should use Repeatable Read isolation when their applications require consistent reads of the same data within a transaction, such as in financial systems where account balances must not change between multiple reads. It is also useful in scenarios involving complex reporting or data analysis where intermediate results need to remain stable. This level balances consistency with concurrency, avoiding the stricter locks of Serializable isolation.

Learning Resources

• docs: PostgreSQL Documentation: Transaction Isolation
• docs: MySQL Documentation: InnoDB Transaction Isolation Levels
• docs: Microsoft SQL Server Isolation Levels
• video: YouTube: Database Isolation Levels Explained
• course: Coursera: Database Management Essentials