feat: support for SQL aggregate functions SUM, AVG, MIN, and MAX to the Repository API (#9737)

* feat: Add support for SQL aggregate functions SUM, AVG, MIN, and MAX to the Repository API

* rename field name to make tests work in oracle

* fix the comments

* update the docs

* escape column name

* address PR comment

* format the code

Author: netroy

docs/repository-api.md

@@ -273,6 +273,30 @@ const count = await repository.count({
 const count = await repository.countBy({ firstName: "Timber" })
 ```
 
+-   `sum` - Returns the sum of a numeric field for all entities that match `FindOptionsWhere`.
+
+```typescript
+const sum = await repository.sum("age", { firstName: "Timber" })
+```
+
+-   `average` - Returns the average of a numeric field for all entities that match `FindOptionsWhere`.
+
+```typescript
+const average = await repository.average("age", { firstName: "Timber" })
+```
+
+-   `minimum` - Returns the minimum of a numeric field for all entities that match `FindOptionsWhere`.
+
+```typescript
+const minimum = await repository.minimum("age", { firstName: "Timber" })
+```
+
+-   `maximum` - Returns the maximum of a numeric field for all entities that match `FindOptionsWhere`.
+
+```typescript
+const maximum = await repository.maximum("age", { firstName: "Timber" })
+```
+
 -   `find` - Finds entities that match given `FindOptions`.
 
 ```typescript

src/common/PickKeysByType.ts

@@ -0,0 +1,7 @@
+/**
+ * Pick only the keys that match the Type `U`
+ */
+export type PickKeysByType<T, U> = string &
+    keyof {
+        [P in keyof T as T[P] extends U ? P : never]: T[P]
+    }

src/entity-manager/EntityManager.ts

@@ -37,6 +37,7 @@ import { getMetadataArgsStorage } from "../globals"
 import { UpsertOptions } from "../repository/UpsertOptions"
 import { InstanceChecker } from "../util/InstanceChecker"
 import { ObjectLiteral } from "../common/ObjectLiteral"
+import { PickKeysByType } from "../common/PickKeysByType"
 
 /**
  * Entity manager supposed to work with any entity, automatically find its repository and call its methods,
@@ -1001,6 +1002,69 @@ export class EntityManager {
             .getCount()
     }
 
+    /**
+     * Return the SUM of a column
+     */
+    sum<Entity extends ObjectLiteral>(
+        entityClass: EntityTarget<Entity>,
+        columnName: PickKeysByType<Entity, number>,
+        where?: FindOptionsWhere<Entity> | FindOptionsWhere<Entity>[],
+    ): Promise<number | null> {
+        return this.callAggregateFun(entityClass, "SUM", columnName, where)
+    }
+
+    /**
+     * Return the AVG of a column
+     */
+    average<Entity extends ObjectLiteral>(
+        entityClass: EntityTarget<Entity>,
+        columnName: PickKeysByType<Entity, number>,
+        where?: FindOptionsWhere<Entity> | FindOptionsWhere<Entity>[],
+    ): Promise<number | null> {
+        return this.callAggregateFun(entityClass, "AVG", columnName, where)
+    }
+
+    /**
+     * Return the MIN of a column
+     */
+    minimum<Entity extends ObjectLiteral>(
+        entityClass: EntityTarget<Entity>,
+        columnName: PickKeysByType<Entity, number>,
+        where?: FindOptionsWhere<Entity> | FindOptionsWhere<Entity>[],
+    ): Promise<number | null> {
+        return this.callAggregateFun(entityClass, "MIN", columnName, where)
+    }
+
+    /**
+     * Return the MAX of a column
+     */
+    maximum<Entity extends ObjectLiteral>(
+        entityClass: EntityTarget<Entity>,
+        columnName: PickKeysByType<Entity, number>,
+        where?: FindOptionsWhere<Entity> | FindOptionsWhere<Entity>[],
+    ): Promise<number | null> {
+        return this.callAggregateFun(entityClass, "MAX", columnName, where)
+    }
+
+    private async callAggregateFun<Entity extends ObjectLiteral>(
+        entityClass: EntityTarget<Entity>,
+        fnName: "SUM" | "AVG" | "MIN" | "MAX",
+        columnName: PickKeysByType<Entity, number>,
+        where: FindOptionsWhere<Entity> | FindOptionsWhere<Entity>[] = {},
+    ): Promise<number | null> {
+        const metadata = this.connection.getMetadata(entityClass)
+        const result = await this.createQueryBuilder(entityClass, metadata.name)
+            .setFindOptions({ where })
+            .select(
+                `${fnName}(${this.connection.driver.escape(
+                    String(columnName),
+                )})`,
+                fnName,
+            )
+            .getRawOne()
+        return result[fnName] === null ? null : parseFloat(result[fnName])
+    }
+
     /**
      * Finds entities that match given find options.
      */

src/repository/BaseEntity.ts

@@ -15,6 +15,7 @@ import { ObjectUtils } from "../util/ObjectUtils"
 import { QueryDeepPartialEntity } from "../query-builder/QueryPartialEntity"
 import { UpsertOptions } from "./UpsertOptions"
 import { EntityTarget } from "../common/EntityTarget"
+import { PickKeysByType } from "../common/PickKeysByType"
 
 /**
  * Base abstract entity for all entities, used in ActiveRecord patterns.
@@ -408,6 +409,50 @@ export class BaseEntity {
         return this.getRepository<T>().countBy(where)
     }
 
+    /**
+     * Return the SUM of a column
+     */
+    static sum<T extends BaseEntity>(
+        this: { new (): T } & typeof BaseEntity,
+        columnName: PickKeysByType<T, number>,
+        where: FindOptionsWhere<T>,
+    ): Promise<number | null> {
+        return this.getRepository<T>().sum(columnName, where)
+    }
+
+    /**
+     * Return the AVG of a column
+     */
+    static average<T extends BaseEntity>(
+        this: { new (): T } & typeof BaseEntity,
+        columnName: PickKeysByType<T, number>,
+        where: FindOptionsWhere<T>,
+    ): Promise<number | null> {
+        return this.getRepository<T>().average(columnName, where)
+    }
+
+    /**
+     * Return the MIN of a column
+     */
+    static minimum<T extends BaseEntity>(
+        this: { new (): T } & typeof BaseEntity,
+        columnName: PickKeysByType<T, number>,
+        where: FindOptionsWhere<T>,
+    ): Promise<number | null> {
+        return this.getRepository<T>().minimum(columnName, where)
+    }
+
+    /**
+     * Return the MAX of a column
+     */
+    static maximum<T extends BaseEntity>(
+        this: { new (): T } & typeof BaseEntity,
+        columnName: PickKeysByType<T, number>,
+        where: FindOptionsWhere<T>,
+    ): Promise<number | null> {
+        return this.getRepository<T>().maximum(columnName, where)
+    }
+
     /**
      * Finds entities that match given options.
      */

src/repository/Repository.ts

@@ -15,6 +15,7 @@ import { ObjectID } from "../driver/mongodb/typings"
 import { FindOptionsWhere } from "../find-options/FindOptionsWhere"
 import { UpsertOptions } from "./UpsertOptions"
 import { EntityTarget } from "../common/EntityTarget"
+import { PickKeysByType } from "../common/PickKeysByType"
 
 /**
  * Repository is supposed to work with your entity objects. Find entities, insert, update, delete, etc.
@@ -476,6 +477,46 @@ export class Repository<Entity extends ObjectLiteral> {
         return this.manager.countBy(this.metadata.target, where)
     }
 
+    /**
+     * Return the SUM of a column
+     */
+    sum(
+        columnName: PickKeysByType<Entity, number>,
+        where?: FindOptionsWhere<Entity> | FindOptionsWhere<Entity>[],
+    ): Promise<number | null> {
+        return this.manager.sum(this.metadata.target, columnName, where)
+    }
+
+    /**
+     * Return the AVG of a column
+     */
+    average(
+        columnName: PickKeysByType<Entity, number>,
+        where?: FindOptionsWhere<Entity> | FindOptionsWhere<Entity>[],
+    ): Promise<number | null> {
+        return this.manager.average(this.metadata.target, columnName, where)
+    }
+
+    /**
+     * Return the MIN of a column
+     */
+    minimum(
+        columnName: PickKeysByType<Entity, number>,
+        where?: FindOptionsWhere<Entity> | FindOptionsWhere<Entity>[],
+    ): Promise<number | null> {
+        return this.manager.minimum(this.metadata.target, columnName, where)
+    }
+
+    /**
+     * Return the MAX of a column
+     */
+    maximum(
+        columnName: PickKeysByType<Entity, number>,
+        where?: FindOptionsWhere<Entity> | FindOptionsWhere<Entity>[],
+    ): Promise<number | null> {
+        return this.manager.maximum(this.metadata.target, columnName, where)
+    }
+
     /**
      * Finds entities that match given find options.
      */

test/functional/repository/aggregate-methods/entity/Post.ts

@@ -0,0 +1,12 @@
+import { Entity } from "../../../../../src/decorator/entity/Entity"
+import { Column } from "../../../../../src/decorator/columns/Column"
+import { PrimaryColumn } from "../../../../../src/decorator/columns/PrimaryColumn"
+
+@Entity()
+export class Post {
+    @PrimaryColumn()
+    id: number
+
+    @Column()
+    counter: number
+}

test/functional/repository/aggregate-methods/repository-aggregate-methods.ts

@@ -0,0 +1,87 @@
+import "reflect-metadata"
+import {
+    closeTestingConnections,
+    createTestingConnections,
+} from "../../../utils/test-utils"
+import { Repository } from "../../../../src/repository/Repository"
+import { DataSource } from "../../../../src/data-source/DataSource"
+import { Post } from "./entity/Post"
+import { LessThan } from "../../../../src"
+import { expect } from "chai"
+
+describe("repository > aggregate methods", () => {
+    debugger
+    let connections: DataSource[]
+    let repository: Repository<Post>
+
+    before(async () => {
+        connections = await createTestingConnections({
+            entities: [Post],
+            schemaCreate: true,
+            dropSchema: true,
+        })
+        repository = connections[0].getRepository(Post)
+        for (let i = 0; i < 100; i++) {
+            const post = new Post()
+            post.id = i
+            post.counter = i + 1
+            await repository.save(post)
+        }
+    })
+
+    after(() => closeTestingConnections(connections))
+
+    describe("sum", () => {
+        it("should return the aggregate sum", async () => {
+            const sum = await repository.sum("counter")
+            expect(sum).to.equal(5050)
+        })
+
+        it("should return null when 0 rows match the query", async () => {
+            const sum = await repository.sum("counter", { id: LessThan(0) })
+            expect(sum).to.be.null
+        })
+    })
+
+    describe("average", () => {
+        it("should return the aggregate average", async () => {
+            const average = await repository.average("counter")
+            expect(average).to.equal(50.5)
+        })
+
+        it("should return null when 0 rows match the query", async () => {
+            const average = await repository.average("counter", {
+                id: LessThan(0),
+            })
+            expect(average).to.be.null
+        })
+    })
+
+    describe("minimum", () => {
+        it("should return the aggregate minimum", async () => {
+            const minimum = await repository.minimum("counter")
+            expect(minimum).to.equal(1)
+        })
+
+        it("should return null when 0 rows match the query", async () => {
+            const minimum = await repository.minimum("counter", {
+                id: LessThan(0),
+            })
+            expect(minimum).to.be.null
+        })
+    })
+
+    describe("maximum", () => {
+        it("should return the aggregate maximum", async () => {
+            const maximum = await repository.maximum("counter")
+            expect(maximum).to.equal(100)
+        })
+
+        it("should return null when 0 rows match the query", async () => {
+            const maximum = await repository.maximum("counter", {
+                id: LessThan(0),
+            })
+            expect(maximum).to.be.null
+        })
+    })
+})