| --- |
| title: "DB Migration" |
| description: > |
| DB Migration |
| sidebar_position: 3 |
| --- |
| |
| ## Summary |
| Starting in v0.10.0, DevLake provides a lightweight migration tool for executing migration scripts. |
| Both framework itself and plugins define their migration scripts in their own migration folder. |
| The migration scripts are written with gorm in Golang to support different SQL dialects. |
| |
| |
| ## Migration Script |
| Migration script describes how to do database migration. |
| They implement the `Script` interface. |
| When DevLake starts, scripts register themselves to the framework by invoking the `Register` function |
| |
| ```go |
| type Script interface { |
| Up(ctx context.Context, db *gorm.DB) error |
| Version() uint64 |
| Name() string |
| } |
| ``` |
| |
| ## Table `migration_history` |
| |
| The table tracks migration scripts execution and schemas changes. |
| From which, DevLake could figure out the current state of database schemas. |
| |
| |
| ## How It Works |
| 1. Check `migration_history` table, calculate all the migration scripts need to be executed. |
| 2. Sort scripts by Version in ascending order. |
| 3. Execute scripts. |
| 4. Save results in the `migration_history` table. |
