fix(mysql): don't process delete PKs if no rows were affected

packages/mysql/src/mysql-adapter.ts

@@ -427,9 +427,12 @@ export class MySQLQueryResolver<T extends OrmEntity> extends SQLQueryResolver<T>
             `;
 
             const rows = await connection.execAndReturnAll(sql, select.params);
-            const returning = rows[1];
-            const pk = returning[0]['@_pk'];
-            if (pk) deleteResult.primaryKeys = JSON.parse(pk).map(primaryKeyConverted);
+            const affectedRows = rows[0].affectedRows;
+            if (affectedRows) {
+                const returning = rows[1];
+                const pk = returning[0]['@_pk'];
+                deleteResult.primaryKeys = JSON.parse(pk).map(primaryKeyConverted);
+            }
             deleteResult.modified = deleteResult.primaryKeys.length;
         } catch (error: any) {
             error = new DatabaseDeleteError(this.classSchema, 'Could not delete in database', { cause: error });

packages/mysql/tests/mysql.spec.ts

@@ -344,3 +344,43 @@ test('non-object null unions should not render as JSON', async () => {
         {name: 'Thomas', nickName: 'Tom', birthdate: new Date('1960-02-10T00:00:00Z')},
     ]);
 });
+
+test('updates & deletes should ignore previous @_pk session variable if no rows were affected', async () => {
+    @entity.name('model7')
+    class Model {
+        id: number & PrimaryKey & AutoIncrement = 0;
+
+        constructor(public name: string) {}
+    }
+
+    const database = await databaseFactory([Model]);
+    const model = new Model('Peter');
+    await database.persist(model);
+    expect(model.id).toEqual(expect.any(Number));
+
+    // perform update & delete in single database connection to ensure @_pk session variable is shared
+    // between multiple queries. outside a transaction, this is luck of the draw based on connection pooling.
+    await database.transaction(async txn => {
+        {
+            const result = await txn.query(Model).filter({id: model.id}).patchMany({name: 'Paul'});
+            expect(result.primaryKeys[0]).toEqual({ id: model.id });
+        }
+
+        {
+            const result = await txn.query(Model).filter({id: model.id}).deleteMany();
+            expect(result.primaryKeys[0]).toEqual({ id: model.id });
+        }
+
+        // there should be no ID returned if we try to update a non-existent record
+        {
+            const result = await txn.query(Model).filter({id: model.id}).patchMany({name: 'Simon'});
+            expect(result.primaryKeys[0]).toBeUndefined();
+        }
+
+        // there should be no ID returned if we try to delete a non-existent record
+        {
+            const result = await txn.query(Model).filter({id: model.id}).deleteMany();
+            expect(result.primaryKeys[0]).toBeUndefined();
+        }
+    });
+});