Learning PostgreSQL 11 - Third Edition

Transaction isolation levels

The transaction isolation levels define the type of locks acquired on the database objects, such as tables. Also, it defines the degree to which a transaction should be isolated from the data modifications made by any other transaction. A transaction isolation level can be set by the developer by invoking the following SQL statement:

SET TRANSACTION ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED}

The SET TRANSACTION ISOLATION LEVEL statement should be called inside a transaction block before any query, otherwise, it will have no effect. An alternative is to use the following syntax:

BEGIN TRANSACTION ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ ...