a74c900ab1
* docs: add documentation for migration generate cli tool * changed migrations details in marketplace recipe * added generated oas files to action * vale + lint fixes * don't import from src in medusa-config.js * fix generate command in recipe * fix module name
59 lines
2.0 KiB
Plaintext
59 lines
2.0 KiB
Plaintext
export const metadata = {
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title: `${pageNumber} Write Migration`,
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}
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# {metadata.title}
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In this chapter, you'll learn how to create a migration and write it manually.
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## What is a Migration?
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A migration is a class created in a TypeScript or JavaScript file under a module's `migrations` directory. It has two methods:
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- The `up` method reflects changes on the database.
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- The `down` method reverts the changes made in the `up` method.
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---
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## How to Write a Migration?
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The Medusa CLI tool provides a [migrations generate](!resources!/medusa-cli#migrations-generate) command to generate a migration for the specified modules' data models.
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Alternatively, you can manually create a migration file under the `migrations` directory of your module.
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For example:
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```ts title="src/modules/hello/migrations/Migration20240429.ts"
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import { Migration } from "@mikro-orm/migrations"
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export class Migration20240702105919 extends Migration {
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async up(): Promise<void> {
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this.addSql("create table if not exists \"my_custom\" (\"id\" text not null, \"name\" text not null, \"created_at\" timestamptz not null default now(), \"updated_at\" timestamptz not null default now(), \"deleted_at\" timestamptz null, constraint \"my_custom_pkey\" primary key (\"id\"));")
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}
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async down(): Promise<void> {
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this.addSql("drop table if exists \"my_custom\" cascade;")
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}
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}
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```
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The migration's file name should be of the format `Migration{YEAR}{MONTH}{DAY}.ts`. The migration class in the file extends the `Migration` class imported from `@mikro-orm/migrations`.
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In the `up` and `down` method of the migration class, you use the `addSql` method provided by MikroORM's `Migration` class to run PostgreSQL syntax.
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In the example above, the `up` method creates the table `my_custom`, and the `down` method drops the table if the migration is reverted.
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---
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## Run the Migration
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To run your migration, run the following command:
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```bash
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npx medusa migrations run
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```
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This reflects the changes in the database as implemented in the migration's `up` method.
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