[Owncloud] migration issues

[Frank Karlitschek]

Hi guys,

our users often have database issues with upgrading to new ownCloud version. This is bad of course.

I think we have to be careful with changing the DB schema:

1. Our automatic database migration routine can handle simple changes like adding a new field to a table. But you can't expect miracles from it if you do bigger changes. So the basic database structure has to stay compatible. We _can't_ do bigger changes in the database structure otherwise upgrade will break and users will loose data. This is not acceptable. 

2. Indexes. It's great to add indexes to the database for good performance. But please keep in mind that different databases have different limitations. This sometimes even vary from version to version. The migration bug with incompatible indexes is like a zombie. We kill it every few week but it always comes back.
So if you change or add indexes you _have_ to test this with all databases and sometimes be a bit more conservative to stay compatible.


Thanks a lot to everyone who contributes.


Frank