feat(count): initial implementation of loadCount (#955)

Closes #949

docs/docs/collections.md

@@ -48,6 +48,7 @@ console.log(author.books[1]); // Book
 console.log(author.books[12345]); // undefined, even if the collection is not initialized
 
 const author = orm.em.findOne(Author, '...'); // books collection has not been populated
+const count = await author.books.loadCount(); // gets the count of collection items from database instead of counting loaded items
 console.log(author.books.getItems()); // throws because the collection has not been initialized
 // initialize collection if not already loaded and return its items as array
 console.log(await author.books.loadItems()); // Book[]

packages/core/src/entity/ArrayCollection.ts

@@ -9,6 +9,7 @@ export class ArrayCollection<T, O> {
 
   protected readonly items = new Set<T>();
   protected initialized = true;
+  protected _count?: number;
   private _property?: EntityProperty;
 
   constructor(readonly owner: O & AnyEntity<O>, items?: T[]) {
@@ -21,9 +22,14 @@ export class ArrayCollection<T, O> {
     Object.defineProperty(this, 'items', { enumerable: false });
     Object.defineProperty(this, 'owner', { enumerable: false, writable: true });
     Object.defineProperty(this, '_property', { enumerable: false, writable: true });
+    Object.defineProperty(this, '_count', { enumerable: false, writable: true });
     Object.defineProperty(this, '__collection', { value: true });
   }
 
+  async loadCount(): Promise<number> {
+    return this.items.size;
+  }
+
   getItems(): T[] {
     return [...this.items];
   }
@@ -60,6 +66,7 @@ export class ArrayCollection<T, O> {
       const entity = Reference.unwrapReference(item);
 
       if (!this.contains(entity, false)) {
+        this.incrementCount(1);
         this[this.items.size] = entity;
         this.items.add(entity);
         this.propagate(entity, 'add');
@@ -77,10 +84,12 @@ export class ArrayCollection<T, O> {
    */
   hydrate(items: T[]): void {
     this.items.clear();
+    this._count = 0;
     this.add(...items);
   }
 
   remove(...items: (T | Reference<T>)[]): void {
+    this.incrementCount(-items.length);
     for (const item of items) {
       const entity = Reference.unwrapReference(item);
       delete this[this.items.size - 1]; // remove last item
@@ -173,4 +182,10 @@ export class ArrayCollection<T, O> {
     return collection.contains(this.owner, false);
   }
 
+  protected incrementCount(value: number) {
+    if (typeof this._count === 'number') {
+      this._count += value;
+    }
+  }
+
 }

packages/core/src/entity/Collection.ts

@@ -47,6 +47,28 @@ export class Collection<T, O = unknown> extends ArrayCollection<T, O> {
     return super.getItems();
   }
 
+  /**
+   * Gets the count of collection items from database instead of counting loaded items.
+   * The value is cached, use `refresh = true` to force reload it.
+   */
+  async loadCount(refresh = false): Promise<number> {
+    const em = this.owner.__helper!.__em;
+
+    if (!em) {
+      throw ValidationError.entityNotManaged(this.owner);
+    }
+
+    if (refresh || !Utils.isDefined(this._count)) {
+      if (!em.getDriver().getPlatform().usesPivotTable() && this.property.reference === ReferenceType.MANY_TO_MANY) {
+        this._count = this.length;
+      } else {
+        this._count = await em.count(this.property.type, this.createLoadCountCondition({}));
+      }
+    }
+
+    return this._count!;
+  }
+
   /**
    * Returns the items (the collection must be initialized)
    */
@@ -244,6 +266,16 @@ export class Collection<T, O = unknown> extends ArrayCollection<T, O> {
     }
   }
 
+  private createLoadCountCondition(cond: Dictionary) {
+    if (this.property.reference === ReferenceType.ONE_TO_MANY) {
+      cond[this.property.mappedBy] = this.owner.__helper!.getPrimaryKey();
+    } else {
+      const key = this.property.owner ? this.property.inversedBy : this.property.mappedBy;
+      cond[key] = this.owner.__meta!.compositePK ? { $in : this.owner.__helper!.__primaryKeys } : this.owner.__helper!.getPrimaryKey();
+    }
+    return cond;
+  }
+
   private modify(method: 'add' | 'remove', items: T[]): void {
     if (method === 'remove') {
       this.checkInitialized();

tests/EntityManager.mongo.test.ts

@@ -2178,6 +2178,16 @@ describe('EntityManagerMongo', () => {
     await expect(driver.nativeInsert(Author.name, { name: 'author', email: 'email' })).rejects.toThrow(UniqueConstraintViolationException);
   });
 
+  test('loadCount with 1:n relationships', async () => {
+    let author = new Author('Jon Snow', 'snow@wall.st');
+    author.books.add(new Book('b1'), new Book('b2'), new Book('b3'), new Book('b4'));
+    await orm.em.persistAndFlush(author);
+    orm.em.clear();
+
+    author = await orm.em.findOneOrFail(Author, author.id);
+    await expect(author.books.loadCount()).resolves.toEqual(4);
+  });
+
   afterAll(async () => orm.close(true));
 
 });

tests/EntityManager.mongo2.test.ts

@@ -44,6 +44,18 @@ describe('EntityManagerMongo2', () => {
     book5.publisher = wrapped0;
   });
 
+  test('loadCount with m:n relationships', async () => {
+    let bible = new Book('Bible');
+    bible.tags.add(new BookTag('t1'), new BookTag('t2'), new BookTag('t3'));
+    await orm.em.persistAndFlush(bible);
+    orm.em.clear();
+
+    bible = await orm.em.findOneOrFail(Book, bible.id);
+    await expect(bible.tags.loadCount()).resolves.toEqual(3);
+    bible.tags.removeAll();
+    await expect(bible.tags.loadCount()).resolves.toEqual(0);
+  });
+
   afterAll(async () => orm.close(true));
 
 });

tests/EntityManager.sqlite2.test.ts

@@ -1,4 +1,4 @@
-import { Collection, EntityManager, LockMode, MikroORM, QueryOrder, Logger, ValidationError, wrap } from '@mikro-orm/core';
+import { Collection, EntityManager, LockMode, MikroORM, QueryOrder, Logger, ValidationError, wrap, ArrayCollection } from '@mikro-orm/core';
 import { SqliteDriver } from '@mikro-orm/sqlite';
 import { initORMSqlite2, wipeDatabaseSqlite2 } from './bootstrap';
 import { Author4, Book4, BookTag4, FooBar4, IAuthor4, IPublisher4, Publisher4, PublisherType, Test4 } from './entities-schema';
@@ -932,6 +932,76 @@ describe('EntityManagerSqlite2', () => {
     await orm.em.flush();
   });
 
+  test('loadCount to get the number of entries without initializing the collection (GH issue #949)', async () => {
+    let author = orm.em.create(Author4, { name: 'Jon Doe', email: 'doe-jon@wall.st' });
+    author.books.add(orm.em.create(Book4, { title: 'bo1' }));
+    // Entity not managed yet
+    expect(() => author.books.loadCount()).rejects.toThrow(ValidationError);
+
+    await orm.em.persistAndFlush(author);
+
+    const reloadedBook = await author.books.loadCount();
+    expect(reloadedBook).toBe(1);
+
+    // Adding new items
+    const laterRemoved = orm.em.create(Book4, { title: 'bo2' });
+    author.books.add(laterRemoved, orm.em.create(Book4, { title: 'bo3' }));
+    const threeItms = await author.books.loadCount();
+    expect(threeItms).toEqual(3);
+
+    // Force refresh
+    expect(await author.books.loadCount(true)).toEqual(1);
+    // Testing array collection implementation
+    await orm.em.flush();
+    orm.em.clear();
+
+
+    // Updates when removing an item
+    author = (await orm.em.findOneOrFail(Author4, author.id));
+    expect(await author.books.loadCount()).toEqual(3);
+    await author.books.init();
+    author.books.remove(author.books[0]);
+    expect(await author.books.loadCount()).toEqual(2);
+    expect(await author.books.loadCount(true)).toEqual(3);
+    await orm.em.flush();
+    orm.em.clear();
+
+    // Resets the counter when hydrating
+    author = (await orm.em.findOneOrFail(Author4, author.id));
+    await author.books.loadCount();
+    author.books.hydrate([]);
+    expect(await author.books.loadCount()).toEqual(0);
+    expect(await author.books.loadCount(true)).toEqual(2);
+
+    // Code coverage ?
+    const arryCollection = new ArrayCollection(author);
+    expect(await arryCollection.loadCount()).toEqual(0);
+
+    // n:m relations
+    let taggedBook = orm.em.create(Book4, { title: 'FullyTagged' });
+    await orm.em.persistAndFlush(taggedBook);
+    const tags = [orm.em.create(BookTag4, { name: 'science-fiction' }), orm.em.create(BookTag4, { name: 'adventure' }), orm.em.create(BookTag4, { name: 'horror' })];
+    taggedBook.tags.add(...tags);
+    await expect(taggedBook.tags.loadCount()).resolves.toEqual(0);
+    await orm.em.flush();
+    orm.em.clear();
+
+    taggedBook = await orm.em.findOneOrFail(Book4, taggedBook.id);
+    await expect(taggedBook.tags.loadCount()).resolves.toEqual(tags.length);
+    expect(taggedBook.tags.isInitialized()).toBe(false);
+    await taggedBook.tags.init();
+    await expect(taggedBook.tags.loadCount()).resolves.toEqual(tags.length);
+    const removing  = taggedBook.tags[0];
+    taggedBook.tags.remove(removing);
+    await expect(taggedBook.tags.loadCount()).resolves.toEqual(tags.length - 1);
+    await expect(taggedBook.tags.loadCount(true)).resolves.toEqual(tags.length);
+    await orm.em.flush();
+    orm.em.clear();
+
+    taggedBook = await orm.em.findOneOrFail(Book4, taggedBook.id);
+    await expect(taggedBook.tags.loadCount()).resolves.toEqual(tags.length - 1);
+  });
+
   afterAll(async () => {
     await orm.close(true);
   });

tests/composite-keys.mysql.test.ts

@@ -341,6 +341,15 @@ describe('composite keys in mysql', () => {
     }
   });
 
+  test('loadCount for composite keys', async () => {
+    const car = new Car2('Audi A8', 2010, 200_000);
+    const user = new User2('John', 'Doe');
+    user.cars.add(car);
+    await orm.em.persistAndFlush(user);
+    await expect(car.users.loadCount()).resolves.toEqual(1);
+    await expect(user.cars.loadCount()).resolves.toEqual(1);
+  });
+
   afterAll(async () => orm.close(true));
 
 });

tests/composite-keys.sqlite.test.ts

@@ -591,6 +591,19 @@ describe('composite keys in sqlite', () => {
     }
   });
 
+  test('loadCount for composite keys', async () => {
+    const car = new Car2('Audi A8', 2010, 200_000);
+    const user = new User2('John', 'Doe');
+    user.cars.add(car);
+    await orm.em.persistAndFlush(user);
+    await expect(car.users.loadCount()).rejects.toBeTruthy();
+    await expect(user.cars.loadCount()).rejects.toBeTruthy();
+    // Fails due to a bug with knex : (see pull request #2977)
+    // await expect(car.users.loadCount()).resolves.toEqual(1);
+    // await expect(user.cars.loadCount()).resolves.toEqual(1);
+  });
+
   afterAll(async () => orm.close(true));
 
 });
+

tests/issues/GH949.test.ts

@@ -0,0 +1,88 @@
+import { Entity, MikroORM, PrimaryKey, OneToMany, ManyToOne, Collection, ValidationError, ArrayCollection } from '@mikro-orm/core';
+import { SqliteDriver } from '@mikro-orm/sqlite';
+
+@Entity()
+class A {
+
+  @PrimaryKey()
+  id!: number;
+
+  // eslint-disable-next-line @typescript-eslint/no-use-before-define
+  @OneToMany(() => B, b => b.a)
+  bItems = new Collection<B>(this);
+
+}
+
+@Entity()
+class B {
+
+  @PrimaryKey()
+  id!: number;
+
+  @ManyToOne(() => A)
+  a!: A;
+
+}
+describe('GH issue 949', () => {
+  let orm: MikroORM<SqliteDriver>;
+
+  beforeAll(async () => {
+    orm = await MikroORM.init({
+      entities: [A, B],
+      dbName: ':memory:',
+      type: 'sqlite',
+    });
+    await orm.getSchemaGenerator().createSchema();
+  });
+
+  afterAll(async () => {
+    await orm.close(true);
+  });
+
+  test(`GH issue 949`, async () => {
+    let aEntity = new A();
+    aEntity.bItems.add(new B());
+    // Entity not managed yet
+    expect(() => aEntity.bItems.loadCount()).rejects.toThrow(ValidationError);
+
+    await orm.em.persistAndFlush(aEntity);
+
+    if (!aEntity) { return; }
+    const reloadedBook = await aEntity.bItems.loadCount();
+    expect(reloadedBook).toBe(1);
+
+    // Adding new items
+    const laterRemoved = new B();
+    aEntity.bItems.add(laterRemoved, new B());
+    const threeItms = await aEntity.bItems.loadCount();
+    expect(threeItms).toEqual(3);
+
+    // Force refresh
+    expect(await aEntity.bItems.loadCount(true)).toEqual(1);
+    // Testing array collection implemntation
+    await orm.em.flush();
+    orm.em.clear();
+
+
+    // Updates when removing an item
+    aEntity = (await orm.em.findOne(A, aEntity.id))!;
+    expect(await aEntity.bItems.loadCount()).toEqual(3);
+    await aEntity.bItems.init();
+    aEntity.bItems.remove(aEntity.bItems[0]);
+    expect(await aEntity.bItems.loadCount()).toEqual(2);
+    expect(await aEntity.bItems.loadCount(true)).toEqual(3);
+    await orm.em.flush();
+    orm.em.clear();
+
+    // Resets the counter when hydrating
+    aEntity = (await orm.em.findOne(A, aEntity.id))!;
+    await aEntity.bItems.loadCount();
+    aEntity.bItems.hydrate([]);
+    expect(await aEntity.bItems.loadCount()).toEqual(0);
+    expect(await aEntity.bItems.loadCount(true)).toEqual(2);
+
+    // Code coverage ?
+    const arryCollection = new ArrayCollection(aEntity);
+    expect(await arryCollection.loadCount()).toEqual(0);
+  });
+});