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Developer documentation for modifying or removing database migrations

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This commit is contained in:
Quentin Gliech
2025-12-04 15:14:33 +01:00
parent b99722f42a
commit 6c5bba19f9
1 changed files with 27 additions and 1 deletions
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docs/development/database.md
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@@ -40,7 +40,7 @@ cargo sqlx prepare
## Migrations
Migration files live in the `migrations` folder in the `mas-core` crate.
Migration files live in the `migrations` folder in the `mas-storage-pg` crate.
```sh
cd crates/storage-pg/ # Again, in the mas-storage-pg crate folder
@@ -50,3 +50,29 @@ cargo sqlx migrate add [description] # Add new migration files
```
Note that migrations are embedded in the final binary and can be run from the service CLI tool.
### Removing migrations
For various reason, we may want to delete migrations.
In case we do, we *must* declare that migration version as it is fine to be missing.
This is because on startup, MAS will validate that all the applied migrations are known, and warn if some are missing.
To do so, get the migration version and add it to the `ALLOWED_MISSING_MIGRATIONS` array in the `mas-storage-pg` crate.
### Modifying existing migrations
We may want to modify existing migrations to fix mistakes.
In case we do, we *must* save the hash of the original migration file so that MAS can validate it on startup.
To do so, extract the first 16 bytes of the existing applied migration and append it to the `ALLOWED_ALTERNATE_CHECKSUMS` array in the `mas-storage-pg` crate.
```sql
SELECT version, ENCODE(SUBSTRING(checksum FOR 16), 'hex') AS short_checksum
FROM _sqlx_migrations
WHERE version = 20250410000002;
```
```
version | short_checksum
----------------+----------------------------------
20250410000002 | f2b8f120deae27e760d079a30b77eea3
```