How to prevent duplicate data in MyBatis concurrency.

Concurrency duplicate data in MyBatis can be prevented in the following ways:

1. Unique constraints at the database level: By setting appropriate unique constraints in the database, duplicate data can be prevented when inserting or updating data. For example, adding a unique index on a specific field in a table will result in an error if a thread attempts to insert duplicate data during concurrent operations, thereby avoiding duplicate data.
2. Optimistic locking: In MyBatis mapping files, use the optimistic locking mechanism by adding a version number field in the database table and checking if the version number matches when updating data. If it doesn’t match, it means the data has been modified by another thread. You can choose to throw an exception or retry the update operation.
3. Pessimistic Locking: In MyBatis, the pessimistic locking mechanism can be used to lock data when querying to prevent other threads from making modifications. This is achieved by using the database’s lock mechanism, such as SELECT … FOR UPDATE, to lock the queried data in a transaction to ensure data consistency.
4. Concurrent control based on version number: Use the version number in MyBatis to control concurrent operations. Increment the version number each time data is updated and check if the version number matches during the update. If it doesn’t match, it means the data has been modified by another thread. You can choose to throw an exception or retry the update operation.

It is necessary to choose the appropriate concurrency control method according to the specific business scenario to ensure the consistency and correctness of the data.