Migrations

[nickvergessen]

Doctrine vs. ownCloud

I looked into Doctrine and ownCloud Migrations today, to see what would fit better with our needs. I saw that the difference is quite minimal:

• Doctrine comes with dependencies for better symfony support (yml instead of a class etc) and to trigger zend-events (a forth event system in nc?)
• ownCloud migrations have no "revert schema change" thing, but when you dropped a table/column you can't revert it back to get the data magically and I can see this point from DeepD

The code they come with is also rather minimal, since most of the PRs are the actual migrations.

I would now propose to go with ownCloud migration, only with two little changes:

Change 1 - Single type only

They have 3 migration types: schema, sql and simple: https://github.com/owncloud/core/pull/27041/files#diff-333567435f8bef9975c29c5e73ab7dd0R372

I would merge them all into one kind with:

• preSchemaChange
• schemaChange
• postSchemaChange

Any of those can be empty. But it allows you e.g. to store data inmemory instead of temp dir, change your db schema and then restore the data again, like we already did it in https://github.com/nextcloud/server/blob/master/apps/twofactor_backupcodes/lib/Migration/CopyEntriesFromOldTable.php

If you dont change the schema, you just leave it unchanged and only change your data in pre/post.

Change 2 - Location

They have the migration files in appinfo/Migrations/ and load them via require_once. I would chose lib/Migration so we have normal autoloading.

cc @LukasReschke @rullzer

[ChristophWurst]

I would chose lib/Migration so we have normal autoloading.

seconded 👍

[LukasReschke]

Change 1 - Single type only

👍

Change 2 - Location

👍

[rullzer]

I like the approach. Sounds clean!

🚀 👍

[nickvergessen]

Found a little issue.
Currently migrations are "dated": 'Version' . date('YmdHis')

However when you have multiple major branches, or introduce a migration in an older version, it will skip all "older" migrations from the newer major branch are not executed anymore. So I propose to add a version in between which is given by the developer: 'VersionXYDate' . date('YmdHis')

This allows us to to correctly sort them. The thing is the engine only can sort by name, and doesn't sort by branch or whatever