2e16949979
* docs: update imports and package names across docs + reference configs * generate files * fix import * change preview to rc
106 lines
3.4 KiB
Plaintext
106 lines
3.4 KiB
Plaintext
export const metadata = {
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title: `${pageNumber} Data Models`,
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}
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# {metadata.title}
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In this chapter, you’ll learn what data models are and how to create a data model.
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## What is a Data Model?
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A data model is a class that represents a table in the database.
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A data model is created in a module, and its record are managed in the database using the module's service.
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---
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## How to Create a Data Model?
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A data model is created in a TypeScript or JavaScript file under a module's `models` directory. It's defined using the `model` utility imported from `@medusajs/framework/utils`.
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For example, create the file `src/modules/hello/models/my-custom.ts` with the following content:
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```ts title="src/modules/hello/models/my-custom.ts"
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import { model } from "@medusajs/framework/utils"
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const MyCustom = model.define("my_custom", {
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id: model.id().primaryKey(),
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name: model.text(),
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})
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export default MyCustom
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```
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You define a data model using the `model`'s `define` method. It accepts two parameters:
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1. The first one is the name of the data model's table in the database. It should be in snake-case form.
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2. The second is an object, which is the data model's schema. The schema's properties are defined using the `model`'s methods.
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The example above defines the data model `MyCustom` with the properties `id` and `name`.
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### Generate a Migration
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A migration is a TypeScript or JavaScript file that defines changes to be made in the database, such as creating a new table or updating it.
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To generate a migration for the data models in your module, run the following command:
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```bash
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npx medusa db:generate helloModuleService
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```
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The `db:generate` command of the Medusa CLI accepts one or more module names to generate the migration for.
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The module name (for example, `helloModuleService`) is the key used when registering the module in the `modules` configuration in `medusa-config.js`.
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The above command creates a migration file at the directory `src/modules/hello/migrations` similar to the following:
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```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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In the migration class, the `up` method creates the table `my_custom` and defines its columns. The `down` method drops the table.
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<Note>
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Data models automatically have the date properties `created_at`, `updated_at`, and `deleted_at`.
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</Note>
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### Run Migration
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To reflect the changes in the generated migration file, run the `migration` command:
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```bash
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npx medusa db:migrate
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```
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If ran successfully, the `my_custom` table will be created in the database.
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---
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## When to Use Data Models
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<Note title="Use data models when" type="success">
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You want to store data related to your customization in the database.
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</Note>
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<Note title="Don't use data models if" type="error">
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You want to store simple key-value pairs related to an existing data model. Instead, use the `metadata` field that most existing models have, which is an object of custom key-value pairs.
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</Note>
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