[Koha-devel] Rolling DB upgrades

[Julian Maurice]

Le 02/03/2021 à 16:00, Joonas Kylmälä a écrit :
> With rolling upgrade we would first create another
> column with the new name and write & read data to both columns during
> the 1st step of upgrade, then in 2nd step when all web server nodes are
> using latest version we could upgrade again to newer version and just
> delete the old column and start using new one.

Does it mean that the application (Perl) code should be aware of that 
intermediary state where both columns exist at the same time ? If so, 
for how long should it be aware of that old database state ?

Does it mean that, for every database schema update, you have to do 
something like this:
- git reset --hard commit_for_1st_step
- updatedatabase (add new column) && reload starman
- git reset --hard commit_for_2nd_step
- updatedatabase (remove old column) && reload starman
?

Do you know another open source software that allows rolling upgrade ? 
It seems like a great idea, but from what I just read online it looks 
really hard to do it correctly.

-- 
Julian Maurice
BibLibre