feat(core): allow disabling transactions

Is it now possible to disable transactions, either globally via `disableTransactions` config option, or locally when using `em.transactional()`.

```ts
// only the outer transaction will be opened
await orm.em.transactional(async em => {
  // but the inner calls to both em.transactional and em.begin will be no-op
  await em.transactional(...);
}, { disableTransactions: true });
```

Alternatively, you can disable transactions when creating new forks:

```ts
const em = await orm.em.fork({ disableTransactions: true });
await em.transactional(...); // no-op
await em.begin(...); // no-op
await em.commit(...); // commit still calls `flush`
```

Closes #3747
Closes #3992

docs/docs/transactions.md

@@ -270,7 +270,7 @@ const res = await em.find(User, { name: 'Jon' }, {
 //   for update of "e0" skip locked
 ```
 
-### Isolation levels
+## Isolation levels
 
 We can set the transaction isolation levels:
 
@@ -288,4 +288,25 @@ Available isolation levels:
 - `IsolationLevel.REPEATABLE_READ`
 - `IsolationLevel.SERIALIZABLE`
 
+## Disabling transactions
+
+Since v5.7 is it possible to disable transactions, either globally via `disableTransactions` config option, or locally when using `em.transactional()`.
+
+```ts
+// only the outer transaction will be opened
+await orm.em.transactional(async em => {
+  // but the inner calls to both em.transactional and em.begin will be no-op
+  await em.transactional(...);
+}, { disableTransactions: true });
+```
+
+Alternatively, you can disable transactions when creating new forks:
+
+```ts
+const em = await orm.em.fork({ disableTransactions: true });
+await em.transactional(...); // no-op
+await em.begin(...); // no-op
+await em.commit(...); // commit still calls `flush`
+```
+
 > This part of documentation is highly inspired by [doctrine internals docs](https://www.doctrine-project.org/projects/doctrine-orm/en/latest/reference/transactions-and-concurrency.html) as the behaviour here is pretty much the same.

packages/core/src/EntityManager.ts

@@ -68,6 +68,7 @@ export class EntityManager<D extends IDatabaseDriver = IDatabaseDriver> {
   private filters: Dictionary<FilterDef> = {};
   private filterParams: Dictionary<Dictionary> = {};
   private transactionContext?: Transaction;
+  private disableTransactions = this.config.get('disableTransactions');
   private flushMode?: FlushMode;
 
   /**
@@ -824,10 +825,16 @@ export class EntityManager<D extends IDatabaseDriver = IDatabaseDriver> {
    */
   async transactional<T>(cb: (em: D[typeof EntityManagerType]) => Promise<T>, options: TransactionOptions = {}): Promise<T> {
     const em = this.getContext(false);
+
+    if (this.disableTransactions) {
+      return cb(em);
+    }
+
     const fork = em.fork({
       clear: false, // state will be merged once resolves
       flushMode: options.flushMode,
       cloneEventManager: true,
+      disableTransactions: options.ignoreNestedTransactions,
     });
     options.ctx ??= em.transactionContext;
 
@@ -858,7 +865,11 @@ export class EntityManager<D extends IDatabaseDriver = IDatabaseDriver> {
   /**
    * Starts new transaction bound to this EntityManager. Use `ctx` parameter to provide the parent when nesting transactions.
    */
-  async begin(options: TransactionOptions = {}): Promise<void> {
+  async begin(options: Omit<TransactionOptions, 'ignoreNestedTransactions'> = {}): Promise<void> {
+    if (this.disableTransactions) {
+      return;
+    }
+
     const em = this.getContext(false);
     em.transactionContext = await em.getConnection('write').begin({ ...options, eventBroadcaster: new TransactionEventBroadcaster(em) });
   }
@@ -869,6 +880,11 @@ export class EntityManager<D extends IDatabaseDriver = IDatabaseDriver> {
   async commit(): Promise<void> {
     const em = this.getContext(false);
 
+    if (this.disableTransactions) {
+      await em.flush();
+      return;
+    }
+
     if (!em.transactionContext) {
       throw ValidationError.transactionRequired();
     }
@@ -882,6 +898,10 @@ export class EntityManager<D extends IDatabaseDriver = IDatabaseDriver> {
    * Rollbacks the transaction bound to this EntityManager.
    */
   async rollback(): Promise<void> {
+    if (this.disableTransactions) {
+      return;
+    }
+
     const em = this.getContext(false);
 
     if (!em.transactionContext) {
@@ -1357,6 +1377,7 @@ export class EntityManager<D extends IDatabaseDriver = IDatabaseDriver> {
     em.config.set('allowGlobalContext', true);
     const fork = new (em.constructor as typeof EntityManager)(em.config, em.driver, em.metadata, options.useContext, eventManager);
     fork.setFlushMode(options.flushMode ?? em.flushMode);
+    fork.disableTransactions = options.disableTransactions ?? this.disableTransactions ?? this.config.get('disableTransactions');
     em.config.set('allowGlobalContext', allowGlobalContext);
 
     fork.filters = { ...em.filters };
@@ -1677,5 +1698,8 @@ export interface ForkOptions {
   cloneEventManager?: boolean;
   /** use this flag to ignore current async context - this is required if we want to call `em.fork()` inside the `getContext` handler */
   disableContextResolution?: boolean;
+  /** set flush mode for this fork, overrides the global option, can be overridden locally via FindOptions */
   flushMode?: FlushMode;
+  /** disable transactions for this fork */
+  disableTransactions?: boolean;
 }

packages/core/src/enums.ts

@@ -169,6 +169,7 @@ export interface TransactionOptions {
   ctx?: Transaction;
   isolationLevel?: IsolationLevel;
   flushMode?: FlushMode;
+  ignoreNestedTransactions?: boolean;
 }
 
 export abstract class PlainObject {

packages/core/src/platforms/Platform.ts

@@ -30,7 +30,7 @@ export abstract class Platform {
   }
 
   supportsTransactions(): boolean {
-    return true;
+    return !this.config.get('disableTransactions');
   }
 
   usesImplicitTransactions(): boolean {

packages/core/src/utils/Configuration.ts

@@ -508,6 +508,7 @@ export interface MikroORMOptions<D extends IDatabaseDriver = IDatabaseDriver> ex
   driverOptions: Dictionary;
   namingStrategy?: { new(): NamingStrategy };
   implicitTransactions?: boolean;
+  disableTransactions?: boolean;
   connect: boolean;
   verbose: boolean;
   autoJoinOneToOneOwner: boolean;

packages/mongodb/src/MongoEntityManager.ts

@@ -31,7 +31,7 @@ export class MongoEntityManager<D extends MongoDriver = MongoDriver> extends Ent
   /**
    * @inheritDoc
    */
-  async begin(options: TransactionOptions & MongoTransactionOptions = {}): Promise<void> {
+  async begin(options: Omit<TransactionOptions, 'ignoreNestedTransactions'> & MongoTransactionOptions = {}): Promise<void> {
     return super.begin(options);
   }
 

tests/features/disable-transactions/disable-nested-transactions.test.ts

@@ -0,0 +1,139 @@
+import { MikroORM } from '@mikro-orm/sqlite';
+import { Entity, PrimaryKey, Property } from '@mikro-orm/core';
+import { mockLogger } from '../../helpers';
+
+@Entity()
+export class Example {
+
+  @PrimaryKey()
+  id!: number;
+
+  @Property()
+  name!: string;
+
+}
+
+let orm: MikroORM;
+
+beforeEach(async () => {
+  orm = await MikroORM.init({
+    entities: [Example],
+    dbName: ':memory:',
+  });
+  await orm.schema.refreshDatabase();
+});
+
+afterEach(async () => {
+  await orm.close(true);
+});
+
+test('should only commit once', async () => {
+  const mock = mockLogger(orm, ['query']);
+
+  await orm.em.transactional(async em => {
+    await em.transactional(async () => {
+      em.create(Example, { name: 'foo' });
+
+      await em.flush();
+
+      const count = await em.count(Example);
+
+      expect(count).toBe(1);
+    });
+
+    em.create(Example, { name: 'bar' });
+
+    await em.flush();
+
+    const count = await em.count(Example);
+
+    expect(count).toBe(2);
+  }, { ignoreNestedTransactions: true });
+
+  const count = await orm.em.count(Example);
+
+  expect(count).toBe(2);
+
+  expect(mock.mock.calls).toHaveLength(7);
+  expect(mock.mock.calls[0][0]).toMatch('begin');
+  expect(mock.mock.calls[1][0]).toMatch('insert into `example` (`name`) values (?) returning `id`');
+  expect(mock.mock.calls[2][0]).toMatch('select count(*) as `count` from `example` as `e0`');
+  expect(mock.mock.calls[3][0]).toMatch('insert into `example` (`name`) values (?) returning `id`');
+  expect(mock.mock.calls[4][0]).toMatch('select count(*) as `count` from `example` as `e0`');
+  expect(mock.mock.calls[5][0]).toMatch('commit');
+  expect(mock.mock.calls[6][0]).toMatch('select count(*) as `count` from `example` as `e0`');
+});
+
+test('should handle rollback in real transaction', async () => {
+  const mock = mockLogger(orm, ['query']);
+
+  const transaction = orm.em.transactional(async em => {
+    await em.transactional(async () => {
+      em.create(Example, { name: 'foo' });
+
+      await em.flush();
+
+      const count = await em.count(Example);
+
+      expect(count).toBe(1);
+    });
+
+    em.create(Example, { name: 'bar' });
+
+    await em.flush();
+
+    const count = await em.count(Example);
+
+    expect(count).toBe(2);
+
+    throw new Error('roll me back');
+  }, { ignoreNestedTransactions: true });
+
+  await expect(transaction).rejects.toThrowError('roll me back');
+
+  const count = await orm.em.count(Example);
+
+  expect(count).toBe(0);
+
+  expect(mock.mock.calls).toHaveLength(7);
+  expect(mock.mock.calls[0][0]).toMatch('begin');
+  expect(mock.mock.calls[1][0]).toMatch('insert into `example` (`name`) values (?) returning `id`');
+  expect(mock.mock.calls[2][0]).toMatch('select count(*) as `count` from `example` as `e0`');
+  expect(mock.mock.calls[3][0]).toMatch('insert into `example` (`name`) values (?) returning `id`');
+  expect(mock.mock.calls[4][0]).toMatch('select count(*) as `count` from `example` as `e0`');
+  expect(mock.mock.calls[5][0]).toMatch('rollback');
+  expect(mock.mock.calls[6][0]).toMatch('select count(*) as `count` from `example` as `e0`');
+});
+
+test('should handle rollback in no-op transaction', async () => {
+  const mock = mockLogger(orm, ['query']);
+
+  const transaction = orm.em.transactional(async em => {
+    await em.transactional(async () => {
+      em.create(Example, { name: 'foo' });
+
+      await em.flush();
+
+      const count = await em.count(Example);
+
+      expect(count).toBe(1);
+
+      throw new Error('roll me back');
+    });
+
+    throw new Error('should not get here');
+  }, { ignoreNestedTransactions: true });
+
+  await expect(transaction).rejects.toThrowError('roll me back');
+
+  const count = await orm.em.count(Example);
+
+  expect(count).toBe(0);
+
+  expect(mock.mock.calls).toHaveLength(5);
+  expect(mock.mock.calls[0][0]).toMatch('begin');
+  expect(mock.mock.calls[1][0]).toMatch('insert into `example` (`name`) values (?) returning `id`');
+  expect(mock.mock.calls[2][0]).toMatch('select count(*) as `count` from `example` as `e0`');
+  expect(mock.mock.calls[3][0]).toMatch('rollback');
+  expect(mock.mock.calls[4][0]).toMatch('select count(*) as `count` from `example` as `e0`');
+});