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Add support for horizontal sharding for Rails 6.1+ #108

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alexeisersun
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Since Rails 6.1, it is possible for a model to connect to multiple databases. A minimal example of such application is:

class ApplicationRecord < ActiveRecord::Base
  connects_to shard: {
    defaul: { writing: :primary_db },
    shard_one: { writing: :secondary_db }
  }
end

class User < ApplicationRecord; end

ApplicationRecord.connected_to(shard: :shard_one, role: :writing) do
  User.create!(...) # creates users in secondary_db DB
end

ApplicationRecord.connection_handler.connection_pools.map { |pool|
pool.db_config.configuration_hash[:database] } # [:primary_db,
:secondary_db]

With support for multiple databases for a model, one would have something like this in tests:

DatabaseCleaner[:active_record, db: ApplicationRecord]

DatabaseCleaner.start
DatabaseCleaner.clean

In .clean, however, the bug occurs: it doesn't actually delete or truncate data from the :secondary_db.

To fix the bug, DatabaseCleaner should iterate through all connection pools the model is connected to.

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@alexeisersun Looks good, could you please update your branch with the latest from main? Thanks!

Since Rails 6.1, it is possible for a model to connect to multiple
databases. A minimal example of such application is:

```ruby
class ApplicationRecord < ActiveRecord::Base
  connects_to shard: {
    defaul: { writing: :primary_db },
    shard_one: { writing: :secondary_db }
  }
end

class User < ApplicationRecord; end

ApplicationRecord.connected_to(shard: :shard_one, role: :writing) do
  User.create!(...) # creates users in secondary_db DB
end

ApplicationRecord.connection_handler.connection_pools.map { |pool|
pool.db_config.configuration_hash[:database] } # [:primary_db,
:secondary_db]
```

With support for multiple databases for a model, one would have something like this in tests:

```ruby
DatabaseCleaner[:active_record, db: ApplicationRecord]

DatabaseCleaner.start
DatabaseCleaner.clean
```

In `.clean`, however, the bug occurs: it doesn't actually
delete or truncate data from the :secondary_db.

To fix the bug, DatabaseCleaner should iterate through _all_ connection pools the model is connected to.
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2 participants