louisthomas / Transaction-Isolation-Level-Issue

Simulate the Transaction problem about dirty read, Non-repeatable reads, Phantom reads, Lost update in the H2, MySQL, Postgresql, SQLite,SQL Server databases by Spring Boot JUnit5.

Simulate Transaction Isolation Level

Environment

• Win10
• IntelliJ IDEA 2020.3 (Ultimate Edition)
• Gradle 6.8.3
• Java 8
• Spring Boot 2.3.10.RELEASE

Simulate Concurrent Transaction

Database Setting

Go to here to change your testing database type and you can custom your database ip or port.

# Database Type(h2 mysql postgresql sqlite sqlserver)
database-type=h2

# Change to your custom mysql ip or port
mysql-ip=localhost
mysql-port=3306

# Change to your custom postgresql ip or port
postgresql-ip=localhost
postgresql-port=5432

# Change to your custom sqlserver ip or port
sqlserver-ip=localhost
sqlserver-port=4033

Use the JUnit 5 to test

Database Testing Result

H2

Isolation Level	Dirty Read	Unrepeatable Read	Phantom Read	Lost Update
DEFAULT	not occur	may occur	may occur	may occur
READ_UNCOMMITTED	may occur	may occur	may occur	may occur
READ_COMMITTED	not occur	may occur	may occur	may occur
REPEATABLE_READ	not occur	not occur	not occur	may occur
SERIALIZABLE	not occur	not occur	not occur	may occur

• Isolation Level DEFAULT seems to be equal to READ_COMMITTED.

---

MySQL

Version: MySQL 5.7 InnoDB

Isolation Level	Dirty Read	Unrepeatable Read	Phantom Read	Lost Update
DEFAULT	not occur	not occur	may occur	may occur
READ_UNCOMMITTED	may occur	may occur	may occur	may occur
READ_COMMITTED	not occur	may occur	may occur	may occur
REPEATABLE_READ	not occur	not occur	may occur	may occur
SERIALIZABLE	not occur	not occur	not occur	not occur

• Isolation Level DEFAULT seems to be equal to REPEATABLE_READ.
• In the Lost Update problem, the SERIALIZABLE in Isolation Level must be retried with @Retryable; otherwise, it will throw LockAcquisitionException.

---

PostgreSQL

Version: PostgreSQL 13.2

Isolation Level	Dirty Read	Unrepeatable Read	Phantom Read	Lost Update
DEFAULT	not occur	may occur	may occur	may occur
READ_UNCOMMITTED	not occur	may occur	may occur	may occur
READ_COMMITTED	not occur	may occur	may occur	may occur
REPEATABLE_READ	not occur	not occur	not occur	not occur
SERIALIZABLE	not occur	not occur	not occur	not occur

• Isolation Level DEFAULT seems to be equal to READ_COMMITTED.
• In the Lost Update problem, the REPEATABLE_READ、SERIALIZABLE in Isolation Level must be retried with @Retryable; otherwise, it will throw LockAcquisitionException

---

SQLite

Isolation Level	Dirty Read	Unrepeatable Read	Phantom Read	Lost Update
DEFAULT	not occur	not occur	not occur	not occur
READ_UNCOMMITTED	not occur	not occur	not occur	not occur
SERIALIZABLE	not occur	not occur	not occur	not occur

• SQLite supports only TRANSACTION_SERIALIZABLE and TRANSACTION_READ_UNCOMMITTED.
• SQLite does not support concurrent writing, so you need to perform lock contention or retry writing.

---

SQL Server

Version: Microsoft SQL Server 2019 (RTM-CU10) (KB5001090) - 15.0.4123.1 (X64)

Isolation Level	Dirty Read	Unrepeatable Read	Phantom Read	Lost Update
DEFAULT	not occur	may occur	may occur	may occur
READ_UNCOMMITTED	may occur	may occur	may occur	may occur
READ_COMMITTED	not occur	may occur	may occur	may occur
REPEATABLE_READ	not occur	not occur	may occur	not occur
SERIALIZABLE	not occur	not occur	not occur	not occur

• Isolation Level DEFAULT seems to be equal to READ_COMMITTED.
• In the Lost Update problem, the REPEATABLE_READ、SERIALIZABLE in Isolation Level must be retried with @Retryable; otherwise, it will throw LockAcquisitionException.

---

Reference

• https://medium.com/@chester.yw.chu/%E5%B0%8D%E6%96%BC-mysql-repeatable-read-isolation-%E5%B8%B8%E8%A6%8B%E7%9A%84%E4%B8%89%E5%80%8B%E8%AA%A4%E8%A7%A3-7a9afbac65af
• https://www.baeldung.com/spring-transactional-propagation-isolation
• https://openhome.cc/Gossip/HibernateGossip/IsolationLevel.html