What are the different transaction isolation levels in PostgreSQL?

What are the different transaction isolation levels in PostgreSQL?

PostgreSQL supports four transaction isolation levels: Read Uncommitted, Read Committed, Repeatable Read, and Serializable. Each level defines how transaction integrity is visible to other transactions.

Can you explain the differences between these levels?

Sure!

1. Read Uncommitted: Allows dirty reads, meaning transactions can see uncommitted changes from others.
2. Read Committed: Only sees committed changes, preventing dirty reads but allowing non-repeatable reads.
3. Repeatable Read: Ensures that if a transaction reads a row, it will see the same data if it reads it again, preventing non-repeatable reads but allowing phantom reads.
4. Serializable: The strictest level, it simulates transactions as if they were executed serially, preventing both non-repeatable and phantom reads.

Which level is the most commonly used?

The most commonly used level is Read Committed, as it provides a good balance between performance and data integrity for most applications.

Are there any performance implications with higher isolation levels?

Yes, higher isolation levels like Serializable can lead to increased locking and reduced concurrency, which may impact performance. It's important to choose the right level based on your application's needs.