fix: closing pool incorrectly works on Postgres (#7596)

* fix: Promises never get resolved in specific cases (#6958)

* Limit the number of query runners to remove when releasing one of them
* Add while loop to release all items on the connected query runners list

Closes #6958

* test: Create test for github issue #6958

src/driver/postgres/PostgresDriver.ts

@@ -1051,7 +1051,10 @@ export class PostgresDriver implements Driver {
      * Closes connection pool.
      */
     protected async closePool(pool: any): Promise<void> {
-        await Promise.all(this.connectedQueryRunners.map(queryRunner => queryRunner.release()));
+        while (this.connectedQueryRunners.length) {
+            await this.connectedQueryRunners[0].release();
+        }
+
         return new Promise<void>((ok, fail) => {
             pool.end((err: any) => err ? fail(err) : ok());
         });

src/driver/postgres/PostgresQueryRunner.ts

@@ -127,7 +127,7 @@ export class PostgresQueryRunner extends BaseQueryRunner implements QueryRunner
             this.releaseCallback();
 
         const index = this.driver.connectedQueryRunners.indexOf(this);
-        if (index !== -1) this.driver.connectedQueryRunners.splice(index);
+        if (index !== -1) this.driver.connectedQueryRunners.splice(index, 1);
 
         return Promise.resolve();
     }

test/github-issues/6958/issue-6958.ts

@@ -0,0 +1,28 @@
+import "reflect-metadata";
+import { createTestingConnections, closeTestingConnections, reloadTestingDatabases } from "../../utils/test-utils";
+import { Connection } from "../../../src/connection/Connection";
+import { PostgresDriver } from "../../../src/driver/postgres/PostgresDriver";
+import { expect } from "chai";
+
+describe("github issues > #6958 Promises never get resolved in specific cases", () => {
+
+    let connections: Connection[];
+    before(async () => connections = await createTestingConnections({
+        enabledDrivers: ["postgres"],
+    }));
+    beforeEach(() => reloadTestingDatabases(connections));
+    after(() => closeTestingConnections(connections));
+
+    it("should release all used query runners upon disconnection", () => Promise.all(connections.map(async connection => {
+        const runner1 = connection.createQueryRunner();
+        await runner1.query("SELECT 1 as foo;"); // dummy query to ensure that a database connection is established
+        const runner2 = connection.createQueryRunner();
+        await runner2.query("SELECT 2 as foo;");
+
+        await connection.close();
+
+        expect(runner1.isReleased).to.be.true;
+        expect(runner2.isReleased).to.be.true;
+        expect((connection.driver as PostgresDriver).connectedQueryRunners.length).to.equal(0);
+    })));
+});