feat(schema): add support for timestamp columns in mysql

```ts
@Property({
  columnType: 'timestamp',
  defaultRaw: 'current_timestamp',
  extra: 'on update current_timestamp',
})
updatedAt!: Date;
```

Closes #2386

packages/core/src/decorators/Property.ts

@@ -66,6 +66,8 @@ export type PropertyOptions<T> = {
   serializer?: (value: any) => any;
   serializedName?: string;
   comment?: string;
+  /** mysql only */
+  extra?: string;
 };
 
 export interface ReferenceOptions<T, O> extends PropertyOptions<O> {

packages/core/src/metadata/EntitySchema.ts

@@ -246,8 +246,8 @@ export class EntitySchema<T extends AnyEntity<T> = AnyEntity, U extends AnyEntit
     const tableName = this._meta.collection ?? this._meta.tableName;
 
     if (tableName?.includes('.') && !this._meta.schema) {
-      this._meta.schema = tableName.substr(0, tableName.indexOf('.'));
-      this._meta.collection = tableName.substr(tableName.indexOf('.') + 1);
+      this._meta.schema = tableName.substring(0, tableName.indexOf('.'));
+      this._meta.collection = tableName.substring(tableName.indexOf('.') + 1);
     }
 
     this.initProperties();

packages/core/src/typings.ts

@@ -247,6 +247,8 @@ export interface EntityProperty<T extends AnyEntity<T> = any> {
   serializer?: (value: any) => any;
   serializedName?: string;
   comment?: string;
+  /** mysql only */
+  extra?: string;
   userDefined?: boolean;
 }
 

packages/knex/src/schema/DatabaseTable.ts

@@ -83,6 +83,7 @@ export class DatabaseTable {
         default: prop.defaultRaw,
         enumItems: prop.items?.every(Utils.isString) ? prop.items as string[] : undefined,
         comment: prop.comment,
+        extra: prop.extra,
       };
       this.columns[field].unsigned ||= this.columns[field].autoincrement;
       const defaultValue = this.platform.getSchemaHelper()!.normalizeDefaultValue(prop.defaultRaw!, prop.length);

packages/knex/src/schema/SchemaComparator.ts

@@ -370,6 +370,10 @@ export class SchemaComparator {
       changedProperties.add('enumItems');
     }
 
+    if ((column1.extra || '').toLowerCase() !== (column2.extra || '').toLowerCase()) {
+      changedProperties.add('extra');
+    }
+
     return changedProperties;
   }
 

packages/knex/src/typings.ts

@@ -45,6 +45,8 @@ export interface Column {
   enumItems?: string[];
   primary?: boolean;
   unique?: boolean;
+  /** mysql only */
+  extra?: string;
 }
 
 export interface ForeignKey {

packages/mysql-base/src/MySqlPlatform.ts

@@ -30,6 +30,7 @@ export class MySqlPlatform extends AbstractSqlPlatform {
     const normalizedType = this.extractSimpleType(type);
     const map = {
       int: 'integer',
+      timestamp: 'datetime',
     };
 
     return super.getMappedType(map[normalizedType] ?? type);

packages/mysql-base/src/MySqlSchemaHelper.ts

@@ -57,10 +57,12 @@ export class MySqlSchemaHelper extends SchemaHelper {
   }
 
   configureColumnDefault(column: Column, col: Knex.ColumnBuilder, knex: Knex, changedProperties?: Set<string>) {
-    if (changedProperties) {
-      col.defaultTo(column.default == null ? null : knex.raw(column.default));
-    } else if (column.default !== undefined) {
-      col.defaultTo(column.default == null ? null : knex.raw(column.default));
+    if (changedProperties || column.default !== undefined) {
+      if (column.default == null) {
+        col.defaultTo(null);
+      } else {
+        col.defaultTo(knex.raw(column.default + (column.extra ? ' ' + column.extra : '')));
+      }
     }
 
     return col;
@@ -145,6 +147,7 @@ export class MySqlSchemaHelper extends SchemaHelper {
         precision: col.numeric_precision,
         scale: col.numeric_scale,
         comment: col.column_comment,
+        extra: col.extra.replace('auto_increment', ''),
       });
     });
   }

tests/features/schema-generator/GH2386.test.ts

@@ -0,0 +1,80 @@
+import { Entity, MikroORM, PrimaryKey, Property } from '@mikro-orm/core';
+import type { MySqlDriver } from '@mikro-orm/mysql';
+
+@Entity({ tableName: 'book' })
+export class Book1 {
+
+  @PrimaryKey()
+  id!: number;
+
+  @Property({ columnType: 'timestamp', defaultRaw: `current_timestamp` })
+  createdAt!: Date;
+
+  @Property({ columnType: 'timestamp', defaultRaw: `current_timestamp`, extra: `on update current_timestamp` })
+  updatedAt!: Date;
+
+}
+
+@Entity({ tableName: 'book' })
+export class Book2 {
+
+  @PrimaryKey()
+  id!: number;
+
+  @Property({ columnType: 'timestamp', defaultRaw: `current_timestamp` })
+  createdAt!: Date;
+
+  @Property({ columnType: 'timestamp', defaultRaw: `current_timestamp` })
+  updatedAt!: Date;
+
+}
+
+@Entity({ tableName: 'book' })
+export class Book3 {
+
+  @PrimaryKey()
+  id!: number;
+
+  @Property({ columnType: 'timestamp', defaultRaw: `current_timestamp` })
+  createdAt!: Date;
+
+  @Property({ columnType: 'timestamp', defaultRaw: `current_timestamp`, extra: `on update current_timestamp` })
+  updatedAt!: Date;
+
+}
+
+describe('changing column in mysql (GH 2386)', () => {
+
+  let orm: MikroORM<MySqlDriver>;
+
+  beforeAll(async () => {
+    orm = await MikroORM.init({
+      entities: [Book1],
+      dbName: `mikro_orm_test_gh_2386`,
+      type: 'mysql',
+      port: 3307,
+    });
+    await orm.getSchemaGenerator().ensureDatabase();
+    await orm.getSchemaGenerator().dropSchema();
+    await orm.getSchemaGenerator().createSchema();
+  });
+
+  afterAll(() => orm.close(true));
+
+  test('schema generator respect indexes on FKs on column update', async () => {
+    const diff0 = await orm.getSchemaGenerator().getUpdateSchemaSQL({ wrap: false });
+    expect(diff0).toBe('');
+    await orm.discoverEntity(Book2);
+    orm.getMetadata().reset('Book1');
+    const diff1 = await orm.getSchemaGenerator().getUpdateSchemaSQL({ wrap: false });
+    expect(diff1).toBe('alter table `book` modify `updated_at` timestamp not null default current_timestamp;\n\n');
+    await orm.getSchemaGenerator().execute(diff1);
+
+    await orm.discoverEntity(Book3);
+    orm.getMetadata().reset('Book2');
+    const diff3 = await orm.getSchemaGenerator().getUpdateSchemaSQL({ wrap: false });
+    expect(diff3).toBe('alter table `book` modify `updated_at` timestamp not null default current_timestamp on update current_timestamp;\n\n');
+    await orm.getSchemaGenerator().execute(diff3);
+  });
+
+});