Patterns for "data-only" Rails migrations

[skatkov (Stanislav (Stas) Katkov)]

Can you expand on this a bit, what is a data migration?

Migrations that don’t tend to change the schema, but intended to move data around in one database. It might not be a beginner level problem, but a problem that will hit users in a face at some moment.

database evolves, data should be retained and safely migrated. with bigger dataset, things could get rather complicated and not beginner friendly.

[etagwerker (Ernesto Tagwerker)]

@skatkov

While there are couple of gems that address that. It would be nice if Rails would offer a official recommendations for data migrations or maybe even a dedicated migration functionality for data only.

I think this is a good idea. What do you think about the data_migrate gem?

I agree that it would be interesting to have an “official convention” for data migrations and maybe even native support to avoid people getting hurt with this sharp knife:

@samsaffron

I think Rails should certainly document how to use the sharp knife that is disable_ddl_transaction! ,