Motivation / Background

This Pull Request has been created because our team at Shopify is implementing a custom ActiveRecord adapter to integrate with Vitess, and we would like to overload the valid_{column,table}_definition_options methods and add additional valid options for schema migrations. For example:

module ActiveRecord
  module ConnectionAdapters
    class VitessMysql2Adapter < Mysql2Adapter
      ...

      def valid_table_definition_options
        super + [:skip_vschema_migrations, :sharding_keys, :auto_increment]
      end

      def valid_column_definition_options
        super + [:skip_vschema_migrations, :sharding_keys, :auto_increment]
      end
    end
  end
end

Detail

This Pull Request, as the simplest possible change, factors out the various valid_{table,column,primary_key}_definition_options to be a public method on an adapter instance.

This allows subclassing adapters to cleanly override their ancestor class' valid options.

Additional information

I don't see any harm in this, maybe except the awkwardness of the roundabout reference of

TableDefinition#valid_column_definition_options -> SchemaStatements#valid_column_definition_options -> ColumnDefinition::OPTION_NAMES

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.