Rails 7.1.1: UUID support for MariaDB/MySQL is missing -> ActiveStorage setup migration fails to correctly dump the new schema.rb (with primary key type: UUID)

[john-999]

Steps to reproduce

After running the ActiveStorage setup, the migration producing the new schema.rb dump appears to fail, the beginning of it looking like this:

ActiveRecord::Schema[7.0].define(version: 2023_09_29_141433) do
# Could not dump table "active_storage_attachments" because of following StandardError
#   Unknown type 'uuid' for column 'id'

# Could not dump table "active_storage_blobs" because of following StandardError
#   Unknown type 'uuid' for column 'id'

# Could not dump table "active_storage_variant_records" because of following StandardError
#   Unknown type 'uuid' for column 'id'
...

In the config/application.rb file, I have added:

config.generators do |g|
  g.orm :active_record, primary_key_type: :uuid
end

However, looking at the generated DB tables in phpMyAdmin, all key and foreign-key values in the "Type" columns correctly show "uuid" (MariaDB supports the UUID data type natively).

System configuration

Rails version: 7.0.4.3
Ruby version: 3.0.1p64 (2021-04-05 revision 0fb782ee38) [x86_64-linux]
MariaDB version: 11.1.2
gem mysql2 version: 0.5.5

[fatkodima]

I cannot reproduce. Could you create a sample rails app that reproduces the issue and share with us? Also note that Rails 7.0 is not supported for bug fixed (see https://guides.rubyonrails.org/maintenance_policy.html), so test against 7.1+.

[john-999]

Yes, I have reproduced the issue in a new sample Rails 7.1.1 app: as_tables_in_schema_dump.zip

1. Download the attached .zipped app folder, and uncompress it to your preferred location.
2. Find the error messages in the file db/schema.rb.

If you want to work on/with this app directly:

3. Make sure the above mentioned System configuration is satisfied.
4. Ensure presence of gems: $ bundle install
5. Set your database user and password: $ rails credentials:edit
6. Create the new database: $ rails db:create
7. Create the ActiveStorage tables: $ rails db:migrate
8. Optionally: Reproduce the error by regenerating the file db/schema.rb: $ rails db:rollback, then $ rails db:migrate, see the error messages in the file db/schema.rb.

If you wish to recreate your own sample app to work with, here are the steps:

1. Make sure the above mentioned System configuration is satisfied.
2. Create the new app: $ rails new as_tables_in_schema_dump
3. Configure + install gem in Gemfile: gem "mysql2", "~> 0.5.3", then $ bundle install.
4. Configure file: database.yml
5. Set your database user and password: $ rails credentials:edit
6. Create the new database: $ rails db:create
7. Add in file: config/application.rb:

config.generators do |g|
  g.orm :active_record, primary_key_type: :uuid
end

8. Set up ActiveStorage: $ rails active_storage:install
9. Run the copied migrations: $ rails db:migrate
10. See the errors in the file db/schema.rb.

EDIT:

Could it be that the errors in the file schema.rb are caused by the gem mysql2? Does this gem play a role during the execution of the task db:schema:dump? In other words: Does it need to have some kind of explicit support for UUID built in?
(I do not have the skills to answer this question.)

[fatkodima]

Thanks, was able to reproduce. Will look into it.

[fatkodima]

Was this working before? Seems like tables with uuid columns are not dumped in schema.rb. I haven't investigated, but does Rails support uuids for MariaDB at all?

cc @matthewd @kamipo @rafaelfranca

[john-999]

I don't know if uuid columns in general have worked before in Rails, for MariaDB/MySQL.

FWIW, what I do know is that uuid is an important feature, that MariaDB is a popular DB, and that Rails correctly creates uuid columns in MariaDB which has support for uuid.

(It is only the schema.rb dump in Rails that fails).

[rafaelfranca]

If it is supported in the mysql adapter, it should also work for MariaDB

[john-999]

@rafaelfranca - If you're referring to the gem mysql2, then take a look at what the creator of the gem says: brianmario/mysql2#1337

So, if I understand correctly, Rails uuid support for MariaDB/MySQL entirely depends on the intention of @brianmario, correct?

[fatkodima]

uuids are working in migrations, because we can specify basically any type in t.column :column_name, :some_type and it will work. But it is not dumped into the schema file.

I was asking if it was supported, because I was surprised to not found it in mysql rails adapter, but it is explicitly supported in postgres adapter. Maybe I am missing something?

I can try to work on introducing it into rails, if desired.