---
title: Automatic migration planning
id: auto-plan
---

import InstallationInstructions from '../components/_installation_instructions.mdx';
import AtlasMigrateDiff from '../components/_atlas_migrate_diff.mdx';

## Automatic migration planning

One of the convenient features of Automatic Migrations is that developers do not
need to write the SQL statements to create or modify the database schema. To 
achieve similar benefits, we will now add a script to our project that will 
automatically plan migration files for us based on the changes to our schema. 

To do this, Ent uses [Atlas](https://atlasgo.io), an open-source tool for managing database
schemas, created by the same people behind Ent. 

If you have been following our example repo, we have been using SQLite as our database
until this point. To demonstrate a more realistic use case, we will now switch to MySQL.
See this change in [PR #3](https://github.com/rotemtam/ent-versioned-migrations-demo/pull/3/files).

## Using the Atlas CLI to plan migrations

In this section, we will demonstrate how to use the Atlas CLI to automatically plan
schema migrations for us. In the past, users had to create a custom Go program to
do this (as described [here](07-programmatically.mdx)). With recent versions of Atlas,
this is no longer necessary: Atlas can natively load the desired databaes schema from an Ent schema.

<InstallationInstructions />

Then, run the following command to automatically generate migration files for your Ent schema:

<AtlasMigrateDiff/>

:::info The role of the [dev database](https://atlasgo.io/concepts/dev-database)
Atlas loads the **current state** by executing the SQL files stored in the migration directory onto the provided
[dev database](https://atlasgo.io/concepts/dev-database). It then compares this state against the **desired state**
defined by the `ent/schema` package and writes a migration plan for moving from the current state to the desired state.
:::


Next, let's see how to upgrade an existing production database to be managed with versioned migrations. 
