# Migrations

- [Migrations](#migrations)
    - [How migrations work](#how-migrations-work)
    - [Creating a new migration](#creating-a-new-migration)
    - [Running and reverting migrations](#running-and-reverting-migrations)
        - [Faking Migrations and Rollbacks](#faking-migrations-and-rollbacks)
        - [Transaction modes](#transaction-modes)
    - [Generating migrations](#generating-migrations)
    - [DataSource option](#datasource-option)
    - [Timestamp option](#timestamp-option)
    - [Using migration API to write migrations](#using-migration-api-to-write-migrations)

## How migrations work

Once you get into production you'll need to synchronize model changes into the database.
Typically, it is unsafe to use `synchronize: true` for schema synchronization on production once
you get data in your database. Here is where migrations come to help.

A migration is just a single file with sql queries to update a database schema
and apply new changes to an existing database.

Let's say you already have a database and a post entity:

```typescript
import { Entity, Column, PrimaryGeneratedColumn } from "typeorm"

@Entity()
export class Post {
    @PrimaryGeneratedColumn()
    id: number

    @Column()
    title: string

    @Column()
    text: string
}
```

And your entity worked in production for months without any changes.
You have thousands of posts in your database.

Now you need to make a new release and rename `title` to `name`.
What would you do?

You need to create a new migration with the following SQL query (postgres dialect):

```sql
ALTER TABLE "post" ALTER COLUMN "title" RENAME TO "name";
```

Once you run this SQL query your database schema is ready to work with your new codebase.
TypeORM provides a place where you can write such sql queries and run them when needed.
This place is called "migrations".

## Creating a new migration

**Pre-requisites**: [Installing CLI](./using-cli.md#installing-cli)

Before creating a new migration you need to setup your data source options properly:

```ts
import { DataSource } from "typeorm"

export default new DataSource({
    type: "mysql",
    host: "localhost",
    port: 3306,
    username: "test",
    password: "test",
    database: "test",
    entities: [
        /*...*/
    ],
    migrations: [
        /*...*/
    ],
    migrationsTableName: "custom_migration_table",
})
```

Here we setup two options:

- `"migrationsTableName": "migrations"` - Specify this option only if you need the migration table name to be different from `"migrations"`.
- `"migrations": [/*...*/]` - list of migrations that need to be loaded by TypeORM

Once you setup the connection options you can create a new migration using CLI:

```
typeorm migration:create ./path-to-migrations-dir/PostRefactoring

```

Here, `PostRefactoring` is the name of the migration - you can specify any name you want.
After you run the command you can see a new file generated in the "migration" directory
named `{TIMESTAMP}-PostRefactoring.ts` where `{TIMESTAMP}` is the current timestamp when the migration was generated.
Now you can open the file and add your migration sql queries there.

You should see the following content inside your migration:

```typescript
import { MigrationInterface, QueryRunner } from "typeorm"

export class PostRefactoringTIMESTAMP implements MigrationInterface {
    async up(queryRunner: QueryRunner): Promise<void> {}

    async down(queryRunner: QueryRunner): Promise<void> {}
}
```

There are two methods you must fill with your migration code: `up` and `down`.
`up` has to contain the code you need to perform the migration.
`down` has to revert whatever `up` changed.
`down` method is used to revert the last migration.

Inside both `up` and `down` you have a `QueryRunner` object.
All database operations are executed using this object.
Learn more about [query runner](./query-runner.md).

Let's see what the migration looks like with our `Post` changes:

```typescript
import { MigrationInterface, QueryRunner } from "typeorm"

export class PostRefactoringTIMESTAMP implements MigrationInterface {
    async up(queryRunner: QueryRunner): Promise<void> {
        await queryRunner.query(
            `ALTER TABLE "post" RENAME COLUMN "title" TO "name"`,
        )
    }

    async down(queryRunner: QueryRunner): Promise<void> {
        await queryRunner.query(
            `ALTER TABLE "post" RENAME COLUMN "name" TO "title"`,
        ) // reverts things made in "up" method
    }
}
```

## Running and reverting migrations

Once you have a migration to run on production, you can run them using a CLI command:

```
typeorm migration:run -- -d path-to-datasource-config
```

**`typeorm migration:create` and `typeorm migration:generate` will create `.ts` files, unless you use the `o` flag (see more in [Generating migrations](#generating-migrations)). The `migration:run` and `migration:revert` commands only work on `.js` files. Thus the typescript files need to be compiled before running the commands.** Alternatively you can use `ts-node` in conjunction with `typeorm` to run `.ts` migration files.

Example with `ts-node`:

```
npx typeorm-ts-node-commonjs migration:run -- -d path-to-datasource-config
```

Example with `ts-node` in ESM projects:

```
npx typeorm-ts-node-esm migration:run -- -d path-to-datasource-config
```

```
npx typeorm-ts-node-esm migration:generate ./src/migrations/update-post-table -d ./src/data-source.ts
```

This command will execute all pending migrations and run them in a sequence ordered by their timestamps.
This means all sql queries written in the `up` methods of your created migrations will be executed.
That's all! Now you have your database schema up-to-date.

If for some reason you want to revert the changes, you can run:

```
typeorm migration:revert -- -d path-to-datasource-config
```

This command will execute `down` in the latest executed migration.
If you need to revert multiple migrations you must call this command multiple times.

### Faking Migrations and Rollbacks

You can also fake run a migration using the `--fake` flag (`-f` for short). This will add the migration
to the migrations table without running it. This is useful for migrations created after manual changes
have already been made to the database or when migrations have been run externally
(e.g. by another tool or application), and you still would like to keep a consistent migration history.

```
typeorm migration:run --fake
```

This is also possible with rollbacks.

```
typeorm migration:revert --fake
```

### Transaction modes

By default, TypeORM will run all your migrations within a single wrapping transaction.
This corresponds to the `--transaction all` flag.
If you require more fine grained transaction control, you can use the `--transaction each` flag to wrap every migration individually, or the `--transaction none` flag to opt out of wrapping the migrations in transactions altogether.

In addition to these flags, you can also override the transaction behavior on a per-migration basis by setting the `transaction` property on the `MigrationInterface` to `true` or `false`. This only works in the `each` or `none` transaction mode.

```typescript
import { MigrationInterface, QueryRunner } from "typeorm"

export class AddIndexTIMESTAMP implements MigrationInterface {
    transaction = false

    async up(queryRunner: QueryRunner): Promise<void> {
        await queryRunner.query(
            `CREATE INDEX CONCURRENTLY post_names_idx ON post(name)`,
        )
    }

    async down(queryRunner: QueryRunner): Promise<void> {
        await queryRunner.query(`DROP INDEX CONCURRENTLY post_names_idx`)
    }
}
```

## Generating migrations

TypeORM is able to automatically generate migration files with schema changes you made.

Let's say you have a `Post` entity with a `title` column, and you have changed the name `title` to `name`.
You can run following command:

```
typeorm migration:generate PostRefactoring -d path-to-datasource-config
```

If you encounter any error, it require you have the path to migration name and data source. You can try this option

```
typeorm migration:generate -d <path/to/datasource> path/to/migrations/<migration-name>
```

And it will generate a new migration called `{TIMESTAMP}-PostRefactoring.ts` with the following content:

```typescript
import { MigrationInterface, QueryRunner } from "typeorm"

export class PostRefactoringTIMESTAMP implements MigrationInterface {
    async up(queryRunner: QueryRunner): Promise<void> {
        await queryRunner.query(
            `ALTER TABLE "post" ALTER COLUMN "title" RENAME TO "name"`,
        )
    }

    async down(queryRunner: QueryRunner): Promise<void> {
        await queryRunner.query(
            `ALTER TABLE "post" ALTER COLUMN "name" RENAME TO "title"`,
        )
    }
}
```

Alternatively you can also output your migrations as Javascript files using the `o` (alias for `--outputJs`) flag. This is useful for Javascript only projects in which TypeScript additional packages are not installed. This command, will generate a new migration file `{TIMESTAMP}-PostRefactoring.js` with the following content:

```javascript
/**
 * @typedef {import('typeorm').MigrationInterface} MigrationInterface
 */

/**
 * @class
 * @implements {MigrationInterface}
 */
module.exports = class PostRefactoringTIMESTAMP {
    async up(queryRunner) {
        await queryRunner.query(
            `ALTER TABLE "post" ALTER COLUMN "title" RENAME TO "name"`,
        )
    }

    async down(queryRunner) {
        await queryRunner.query(
            `ALTER TABLE "post" ALTER COLUMN "name" RENAME TO "title"`,
        )
    }
}

```
By default, it generates CommonJS JavaScript code with the `o` (alias for `--outputJs`) flag, but you can also generate ESM code with the `esm` flag. This is useful for Javascript projects that use ESM:

```javascript
/**
 * @typedef {import('typeorm').MigrationInterface} MigrationInterface
 */


/**
 * @class
 * @implements {MigrationInterface}
 */
export class PostRefactoringTIMESTAMP {
    async up(queryRunner) {
        await queryRunner.query(
            `ALTER TABLE "post" ALTER COLUMN "title" RENAME TO "name"`,
        )
    }

    async down(queryRunner) {
        await queryRunner.query(
            `ALTER TABLE "post" ALTER COLUMN "name" RENAME TO "title"`,
        )
    }
}
```

See, you don't need to write the queries on your own.
The rule of thumb for generating migrations is that you generate them after **each** change you made to your models. To apply multi-line formatting to your generated migration queries, use the `p` (alias for `--pretty`) flag.

## DataSource option

If you need to run/revert/generate/show your migrations use the `-d` (alias for `--dataSource`) and pass the path to the file where your DataSource instance is defined as an argument

```
typeorm -d <your-data-source-path> migration:{run|revert}
```

## Timestamp option

If you need to specify a timestamp for the migration name, use the `-t` (alias for `--timestamp`) and pass the timestamp (should be a non-negative number)

```
typeorm -t <specific-timestamp> migration:{create|generate}
```

You can get a timestamp from:

```js
Date.now()
/* OR */ new Date().getTime()
```

## Using migration API to write migrations

In order to use an API to change a database schema you can use `QueryRunner`.

Example:

```ts
import {
    MigrationInterface,
    QueryRunner,
    Table,
    TableIndex,
    TableColumn,
    TableForeignKey,
} from "typeorm"

export class QuestionRefactoringTIMESTAMP implements MigrationInterface {
    async up(queryRunner: QueryRunner): Promise<void> {
        await queryRunner.createTable(
            new Table({
                name: "question",
                columns: [
                    {
                        name: "id",
                        type: "int",
                        isPrimary: true,
                    },
                    {
                        name: "name",
                        type: "varchar",
                    },
                ],
            }),
            true,
        )

        await queryRunner.createIndex(
            "question",
            new TableIndex({
                name: "IDX_QUESTION_NAME",
                columnNames: ["name"],
            }),
        )

        await queryRunner.createTable(
            new Table({
                name: "answer",
                columns: [
                    {
                        name: "id",
                        type: "int",
                        isPrimary: true,
                    },
                    {
                        name: "name",
                        type: "varchar",
                    },
                    {
                        name: "created_at",
                        type: "timestamp",
                        default: "now()",
                    },
                ],
            }),
            true,
        )

        await queryRunner.addColumn(
            "answer",
            new TableColumn({
                name: "questionId",
                type: "int",
            }),
        )

        await queryRunner.createForeignKey(
            "answer",
            new TableForeignKey({
                columnNames: ["questionId"],
                referencedColumnNames: ["id"],
                referencedTableName: "question",
                onDelete: "CASCADE",
            }),
        )
    }

    async down(queryRunner: QueryRunner): Promise<void> {
        const table = await queryRunner.getTable("answer")
        const foreignKey = table.foreignKeys.find(
            (fk) => fk.columnNames.indexOf("questionId") !== -1,
        )
        await queryRunner.dropForeignKey("answer", foreignKey)
        await queryRunner.dropColumn("answer", "questionId")
        await queryRunner.dropTable("answer")
        await queryRunner.dropIndex("question", "IDX_QUESTION_NAME")
        await queryRunner.dropTable("question")
    }
}
```

---

```ts
getDatabases(): Promise<string[]>
```

Returns all available database names including system databases.

---

```ts
getSchemas(database?: string): Promise<string[]>
```

- `database` - If database parameter specified, returns schemas of that database

Returns all available schema names including system schemas. Useful for SQLServer and Postgres only.

---

```ts
getTable(tableName: string): Promise<Table|undefined>
```

- `tableName` - name of a table to be loaded

Loads a table by a given name from the database.

---

```ts
getTables(tableNames: string[]): Promise<Table[]>
```

- `tableNames` - name of a tables to be loaded

Loads a tables by a given names from the database.

---

```ts
hasDatabase(database: string): Promise<boolean>
```

- `database` - name of a database to be checked

Checks if database with the given name exist.

---

```ts
hasSchema(schema: string): Promise<boolean>
```

- `schema` - name of a schema to be checked

Checks if schema with the given name exist. Used only for SqlServer and Postgres.

---

```ts
hasTable(table: Table|string): Promise<boolean>
```

- `table` - Table object or name

Checks if table exist.

---

```ts
hasColumn(table: Table|string, columnName: string): Promise<boolean>
```

- `table` - Table object or name
- `columnName` - name of a column to be checked

Checks if column exist in the table.

---

```ts
createDatabase(database: string, ifNotExist?: boolean): Promise<void>
```

- `database` - database name
- `ifNotExist` - skips creation if `true`, otherwise throws error if database already exist

Creates a new database.

---

```ts
dropDatabase(database: string, ifExist?: boolean): Promise<void>
```

- `database` - database name
- `ifExist` - skips deletion if `true`, otherwise throws error if database was not found

Drops database.

---

```ts
createSchema(schemaPath: string, ifNotExist?: boolean): Promise<void>
```

- `schemaPath` - schema name. For SqlServer can accept schema path (e.g. 'dbName.schemaName') as parameter.
  If schema path passed, it will create schema in specified database
- `ifNotExist` - skips creation if `true`, otherwise throws error if schema already exist

Creates a new table schema.

---

```ts
dropSchema(schemaPath: string, ifExist?: boolean, isCascade?: boolean): Promise<void>
```

- `schemaPath` - schema name. For SqlServer can accept schema path (e.g. 'dbName.schemaName') as parameter.
  If schema path passed, it will drop schema in specified database
- `ifExist` - skips deletion if `true`, otherwise throws error if schema was not found
- `isCascade` - If `true`, automatically drop objects (tables, functions, etc.) that are contained in the schema.
  Used only in Postgres.

Drops a table schema.

---

```ts
createTable(table: Table, ifNotExist?: boolean, createForeignKeys?: boolean, createIndices?: boolean): Promise<void>
```

- `table` - Table object.
- `ifNotExist` - skips creation if `true`, otherwise throws error if table already exist. Default `false`
- `createForeignKeys` - indicates whether foreign keys will be created on table creation. Default `true`
- `createIndices` - indicates whether indices will be created on table creation. Default `true`

Creates a new table.

---

```ts
dropTable(table: Table|string, ifExist?: boolean, dropForeignKeys?: boolean, dropIndices?: boolean): Promise<void>
```

- `table` - Table object or table name to be dropped
- `ifExist` - skips dropping if `true`, otherwise throws error if table does not exist
- `dropForeignKeys` - indicates whether foreign keys will be dropped on table deletion. Default `true`
- `dropIndices` - indicates whether indices will be dropped on table deletion. Default `true`

Drops a table.

---

```ts
renameTable(oldTableOrName: Table|string, newTableName: string): Promise<void>
```

- `oldTableOrName` - old Table object or name to be renamed
- `newTableName` - new table name

Renames a table.

---

```ts
addColumn(table: Table|string, column: TableColumn): Promise<void>
```

- `table` - Table object or name
- `column` - new column

Adds a new column.

---

```ts
addColumns(table: Table|string, columns: TableColumn[]): Promise<void>
```

- `table` - Table object or name
- `columns` - new columns

Adds a new column.

---

```ts
renameColumn(table: Table|string, oldColumnOrName: TableColumn|string, newColumnOrName: TableColumn|string): Promise<void>
```

- `table` - Table object or name
- `oldColumnOrName` - old column. Accepts TableColumn object or column name
- `newColumnOrName` - new column. Accepts TableColumn object or column name

Renames a column.

---

```ts
changeColumn(table: Table|string, oldColumn: TableColumn|string, newColumn: TableColumn): Promise<void>
```

- `table` - Table object or name
- `oldColumn` - old column. Accepts TableColumn object or column name
- `newColumn` - new column. Accepts TableColumn object

Changes a column in the table.

---

```ts
changeColumns(table: Table|string, changedColumns: { oldColumn: TableColumn, newColumn: TableColumn }[]): Promise<void>
```

- `table` - Table object or name
- `changedColumns` - array of changed columns.
    - `oldColumn` - old TableColumn object
    - `newColumn` - new TableColumn object

Changes a columns in the table.

---

```ts
dropColumn(table: Table|string, column: TableColumn|string): Promise<void>
```

- `table` - Table object or name
- `column` - TableColumn object or column name to be dropped

Drops a column in the table.

---

```ts
dropColumns(table: Table|string, columns: TableColumn[]|string[]): Promise<void>
```

- `table` - Table object or name
- `columns` - array of TableColumn objects or column names to be dropped

Drops a columns in the table.

---

```ts
createPrimaryKey(table: Table|string, columnNames: string[]): Promise<void>
```

- `table` - Table object or name
- `columnNames` - array of column names which will be primary

Creates a new primary key.

---

```ts
updatePrimaryKeys(table: Table|string, columns: TableColumn[]): Promise<void>
```

- `table` - Table object or name
- `columns` - array of TableColumn objects which will be updated

Updates composite primary keys.

---

```ts
dropPrimaryKey(table: Table|string): Promise<void>
```

- `table` - Table object or name

Drops a primary key.

---

```ts
createUniqueConstraint(table: Table|string, uniqueConstraint: TableUnique): Promise<void>
```

- `table` - Table object or name
- `uniqueConstraint` - TableUnique object to be created

Creates new unique constraint.

> Note: does not work for MySQL, because MySQL stores unique constraints as unique indices. Use `createIndex()` method instead.

---

```ts
createUniqueConstraints(table: Table|string, uniqueConstraints: TableUnique[]): Promise<void>
```

- `table` - Table object or name
- `uniqueConstraints` - array of TableUnique objects to be created

Creates new unique constraints.

> Note: does not work for MySQL, because MySQL stores unique constraints as unique indices. Use `createIndices()` method instead.

---

```ts
dropUniqueConstraint(table: Table|string, uniqueOrName: TableUnique|string): Promise<void>
```

- `table` - Table object or name
- `uniqueOrName` - TableUnique object or unique constraint name to be dropped

Drops an unique constraint.

> Note: does not work for MySQL, because MySQL stores unique constraints as unique indices. Use `dropIndex()` method instead.

---

```ts
dropUniqueConstraints(table: Table|string, uniqueConstraints: TableUnique[]): Promise<void>
```

- `table` - Table object or name
- `uniqueConstraints` - array of TableUnique objects to be dropped

Drops an unique constraints.

> Note: does not work for MySQL, because MySQL stores unique constraints as unique indices. Use `dropIndices()` method instead.

---

```ts
createCheckConstraint(table: Table|string, checkConstraint: TableCheck): Promise<void>
```

- `table` - Table object or name
- `checkConstraint` - TableCheck object

Creates new check constraint.

> Note: MySQL does not support check constraints.

---

```ts
createCheckConstraints(table: Table|string, checkConstraints: TableCheck[]): Promise<void>
```

- `table` - Table object or name
- `checkConstraints` - array of TableCheck objects

Creates new check constraint.

> Note: MySQL does not support check constraints.

---

```ts
dropCheckConstraint(table: Table|string, checkOrName: TableCheck|string): Promise<void>
```

- `table` - Table object or name
- `checkOrName` - TableCheck object or check constraint name

Drops check constraint.

> Note: MySQL does not support check constraints.

---

```ts
dropCheckConstraints(table: Table|string, checkConstraints: TableCheck[]): Promise<void>
```

- `table` - Table object or name
- `checkConstraints` - array of TableCheck objects

Drops check constraints.

> Note: MySQL does not support check constraints.

---

```ts
createForeignKey(table: Table|string, foreignKey: TableForeignKey): Promise<void>
```

- `table` - Table object or name
- `foreignKey` - TableForeignKey object

Creates a new foreign key.

---

```ts
createForeignKeys(table: Table|string, foreignKeys: TableForeignKey[]): Promise<void>
```

- `table` - Table object or name
- `foreignKeys` - array of TableForeignKey objects

Creates a new foreign keys.

---

```ts
dropForeignKey(table: Table|string, foreignKeyOrName: TableForeignKey|string): Promise<void>
```

- `table` - Table object or name
- `foreignKeyOrName` - TableForeignKey object or foreign key name

Drops a foreign key.

---

```ts
dropForeignKeys(table: Table|string, foreignKeys: TableForeignKey[]): Promise<void>
```

- `table` - Table object or name
- `foreignKeys` - array of TableForeignKey objects

Drops a foreign keys.

---

```ts
createIndex(table: Table|string, index: TableIndex): Promise<void>
```

- `table` - Table object or name
- `index` - TableIndex object

Creates a new index.

---

```ts
createIndices(table: Table|string, indices: TableIndex[]): Promise<void>
```

- `table` - Table object or name
- `indices` - array of TableIndex objects

Creates a new indices.

---

```ts
dropIndex(table: Table|string, index: TableIndex|string): Promise<void>
```

- `table` - Table object or name
- `index` - TableIndex object or index name

Drops an index.

---

```ts
dropIndices(table: Table|string, indices: TableIndex[]): Promise<void>
```

- `table` - Table object or name
- `indices` - array of TableIndex objects

Drops an indices.

---

```ts
clearTable(tableName: string): Promise<void>
```

- `tableName` - table name

Clears all table contents.

> Note: this operation uses SQL's TRUNCATE query which cannot be reverted in transactions.

---

```ts
enableSqlMemory(): void
```

Enables special query runner mode in which sql queries won't be executed, instead they will be memorized into a special variable inside query runner.
You can get memorized sql using `getMemorySql()` method.

---

```ts
disableSqlMemory(): void
```

Disables special query runner mode in which sql queries won't be executed. Previously memorized sql will be flushed.

---

```ts
clearSqlMemory(): void
```

Flushes all memorized sql statements.

---

```ts
getMemorySql(): SqlInMemory
```

- returns `SqlInMemory` object with array of `upQueries` and `downQueries` sql statements

Gets sql stored in the memory. Parameters in the sql are already replaced.

---

```ts
executeMemoryUpSql(): Promise<void>
```

Executes memorized up sql queries.

---

```ts
executeMemoryDownSql(): Promise<void>
```

Executes memorized down sql queries.

---
