Transaction Isolation Level Proposal

Issue type:

[ ] question [ ] bug report [x] feature request [ ] documentation issue

It was mentioned in #233 to create an issue defining how one would see isolation levels being used.

I believe it would be as simple as an isolationLevel parameter on the transaction methods. Alternatively an options parameter could be specified with the isolationLevel as a property of those options.

For the EntityManager an overloaded function would be needed in order to specify the options before the callback:

async transaction<T>(isolationLevel: IsolationLevel, runInTransaction: (entityManger: EntityManager) => Promise<T>): Promise<T>;
async transaction<T>(runInTransaction: (entityManger: EntityManager) => Promise<T>): Promise<T> {

  ...

  try {
    if (isolationLevel) {
      await queryRunner.startTransaction(isolationLevel);
    } else {
      await queryRunner.startTransaction();
    }
    const result = await runInTransaction(queryRunner.manager);
    await queryRunner.commitTransaction();
    return result;
    ...
}

For PostgresQueryRunner:

async startTransaction(isolationLevel?: IsolationLevel): Promise<void> {
  if (this.isTransactionActive)
      throw new TransactionAlreadyStartedError();

  this.isTransactionActive = true;
  await this.query("START TRANSACTION");
  if (isolationLevel) {
    await this.query("SET TRANSACTION ISOLATION LEVEL" + isolationLevel)
  }
}

Where the following are defined:

enum IsolationLevel {
  READ_UNCOMMITTED = 'READ UNCOMMITTED',
  READ_COMMITED = 'READ COMMITTED',
  REPEATABLE_READ = 'REPEATABLE READ',
  SERIALIZABLE = 'SERIALIZABLE'
}

Then to use it, it would be as simple as:

getManager().transaction(IsolationLevel.SERIALIZABLE, (manager) => {
  ...
});

References: Postgres MySQL

[deerares]

we have blocking issue that needs to be fixed first before we can release a new version, awaiting for that.

Have any news about this version?

[Kononnable]

0.2.8 was released few months ago, so this issue should be closed for some time 😃