Multiple databases v2

README.md

@@ -224,6 +224,70 @@ class UpdateSearchResultsToVersion2 < ActiveRecord::Migration
 end
 ```
 
+## Can I use Scenic with multiple databases?
+
+You bet! If you're using Rails 6.0 or higher with multiple databases configured,
+Scenic has you covered. Just pass a `--database` option when generating your
+view:
+
+```sh
+$ rails generate scenic:view analytics --database=secondary
+      create  db/secondary_views/analytics_v01.sql
+      create  db/secondary_migrate/[TIMESTAMP]_create_analytics.rb
+```
+
+Scenic will create your view definition in a database-specific directory
+(`db/secondary_views/` instead of `db/views/`) and the generated migration will
+include the `database:` parameter:
+
+```ruby
+class CreateAnalytics < ActiveRecord::Migration[7.0]
+  def change
+    create_view :analytics, database: :secondary
+  end
+end
+```
+
+Run the migration for your secondary database the same way you would for any
+Rails multiple database setup:
+
+```sh
+$ rake db:migrate:secondary
+```
+
+All of Scenic's migration methods accept the `database:` parameter, so you can
+create, update, and drop views on any configured database:
+
+```ruby
+def change
+  create_view :reports, version: 1, database: :secondary
+  update_view :reports, version: 2, database: :secondary
+  drop_view :reports, database: :secondary
+end
+```
+
+If you need custom paths for your views or migrations, you can configure them
+in `database.yml` just like Rails' `migrations_paths`:
+
+```yaml
+# config/database.yml
+secondary:
+  database: my_secondary_db
+  migrations_paths: db/secondary_migrate
+  views_paths: db/secondary_views
+```
+
+If you're using different adapters for different databases (say, Postgres for
+your primary database and MySQL for analytics), you can configure them in an
+initializer:
+
+```ruby
+# config/initializers/scenic.rb
+Scenic.configure do |config|
+  config.databases[:secondary] = Scenic::Adapters::Postgres.new(SecondaryRecord)
+end
+```
+
 ## I don't need this view anymore. Make it go away.
 
 Scenic gives you `drop_view` too:
@@ -232,6 +296,7 @@ Scenic gives you `drop_view` too:
 def change
   drop_view :search_results, revert_to_version: 2
   drop_view :materialized_admin_reports, revert_to_version: 3, materialized: true
+  drop_view :analytics_view, revert_to_version: 1, database: :secondary
 end
 ```
 

lib/generators/scenic/materializable.rb

@@ -27,6 +27,11 @@ module Materializable
           required: false,
           desc: "Uses replace_view instead of update_view",
           default: false
+        class_option :database,
+          type: :string,
+          required: false,
+          desc: "The database to use (requires Rails 6.0+)",
+          default: nil
       end
 
       private
@@ -47,6 +52,20 @@ def side_by_side?
         options[:side_by_side]
       end
 
+      def database
+        options[:database]&.to_sym
+      end
+
+      def validate_rails_version_for_multiple_databases!
+        return unless database
+
+        if Rails::VERSION::MAJOR < 6
+          raise ArgumentError,
+            "Multiple database support requires Rails 6.0 or higher. " \
+            "You are using Rails #{Rails::VERSION::STRING}."
+        end
+      end
+
       def materialized_view_update_options
         set_options = {no_data: no_data?, side_by_side: side_by_side?}
           .select { |_, v| v }

lib/generators/scenic/view/templates/db/migrate/update_view.erb

@@ -5,9 +5,9 @@ class <%= migration_class_name %> < <%= activerecord_migration_class %>
     <%= method_name %> <%= formatted_plural_name %>,
       version: <%= version %>,
       revert_to_version: <%= previous_version %>,
-      materialized: <%= materialized_view_update_options %>
+      materialized: <%= materialized_view_update_options %><%= update_view_options %>
   <%- else -%>
-    <%= method_name %> <%= formatted_plural_name %>, version: <%= version %>, revert_to_version: <%= previous_version %>
+    <%= method_name %> <%= formatted_plural_name %>, version: <%= version %>, revert_to_version: <%= previous_version %><%= update_view_options %>
   <%- end -%>
   end
 end

lib/generators/scenic/view/view_generator.rb

@@ -11,6 +11,10 @@ class ViewGenerator < Rails::Generators::NamedBase
 
       source_root File.expand_path("templates", __dir__)
 
+      def validate_multiple_database_support
+        validate_rails_version_for_multiple_databases!
+      end
+
       def create_views_directory
         unless views_directory_path.exist?
           empty_directory(views_directory_path)
@@ -29,12 +33,12 @@ def create_migration_file
         if creating_new_view? || destroying_initial_view?
           migration_template(
             "db/migrate/create_view.erb",
-            "db/migrate/create_#{plural_file_name}.rb"
+            File.join(migration_directory, "create_#{plural_file_name}.rb")
           )
         else
           migration_template(
             "db/migrate/update_view.erb",
-            "db/migrate/update_#{plural_file_name}_to_version_#{version}.rb"
+            File.join(migration_directory, "update_#{plural_file_name}_to_version_#{version}.rb")
           )
         end
       end
@@ -81,7 +85,51 @@ def file_name
       end
 
       def views_directory_path
-        @views_directory_path ||= Rails.root.join("db", "views")
+        @views_directory_path ||= begin
+          db_config = ActiveRecord::Base.configurations.configs_for(
+            env_name: Rails.env,
+            name: database_name
+          )
+
+          if db_config&.respond_to?(:views_paths) && (configured_path = Array(db_config.views_paths).first)
+            Rails.root.join(configured_path)
+          else
+            conventional_views_path
+          end
+        end
+      end
+
+      def conventional_views_path
+        if database && database != :default
+          Rails.root.join("db", "#{database}_views")
+        else
+          Rails.root.join("db", "views")
+        end
+      end
+
+      def migration_directory
+        db_config = ActiveRecord::Base.configurations.configs_for(
+          env_name: Rails.env,
+          name: database_name
+        )
+
+        Array(db_config&.migrations_paths).first || conventional_migration_path
+      end
+
+      def database_name
+        (database || :primary).to_s
+      end
+
+      def conventional_migration_path
+        if database && database != :default
+          "db/#{database}_migrate"
+        else
+          "db/migrate"
+        end
+      end
+
+      def different_database_set?
+        database && database != :default
       end
 
       def version_regex
@@ -93,11 +141,11 @@ def creating_new_view?
       end
 
       def definition
-        Scenic::Definition.new(plural_file_name, version)
+        Scenic::Definition.new(plural_file_name, version, database)
       end
 
       def previous_definition
-        Scenic::Definition.new(plural_file_name, previous_version)
+        Scenic::Definition.new(plural_file_name, previous_version, database)
       end
 
       def destroying?
@@ -113,8 +161,21 @@ def formatted_plural_name
       end
 
       def create_view_options
+        options = ""
         if materialized?
-          ", materialized: #{no_data? ? "{ no_data: true }" : true}"
+          options << ", materialized: #{no_data? ? "{ no_data: true }" : true}"
+        end
+
+        if different_database_set?
+          options << ", database: :#{database}"
+        end
+
+        options
+      end
+
+      def update_view_options
+        if different_database_set?
+          ", database: :#{database}"
         else
           ""
         end

lib/scenic.rb

@@ -23,11 +23,14 @@ def self.load
     ActiveRecord::SchemaDumper.prepend Scenic::SchemaDumper
   end
 
-  # The current database adapter used by Scenic.
+  # Returns the database adapter for the specified database.
   #
   # This defaults to {Adapters::Postgres} but can be overridden
   # via {Configuration}.
-  def self.database
-    configuration.database
+  #
+  # @param name [Symbol] the database name (defaults to :default)
+  # @return [Scenic::Adapters::Postgres] the database adapter
+  def self.database(name = :default)
+    configuration.database_adapter(name)
   end
 end

lib/scenic/configuration.rb

@@ -1,13 +1,39 @@
 module Scenic
   class Configuration
+    # Collection of database adapters for multi-database support.
+    # Access specific databases using database names as keys.
+    #
+    # @example
+    #   Scenic.configure do |config|
+    #     config.databases[:secondary] = Scenic::Adapters::Postgres.new(SecondaryRecord)
+    #   end
+    #
+    # @return [ActiveSupport::OrderedOptions] hash of database adapters
+    attr_reader :databases
+
     # The Scenic database adapter instance to use when executing SQL.
     #
     # Defaults to an instance of {Adapters::Postgres}
     # @return Scenic adapter
-    attr_accessor :database
+    def database
+      @databases[:default]
+    end
+
+    def database=(adapter)
+      @databases[:default] = adapter
+    end
 
     def initialize
-      @database = Scenic::Adapters::Postgres.new
+      @databases = ActiveSupport::OrderedOptions.new
+      @databases[:default] = Scenic::Adapters::Postgres.new
+    end
+
+    # Returns the database adapter for the specified database name.
+    #
+    # @param name [Symbol] the database name (defaults to :default)
+    # @return [Scenic::Adapters::Postgres] the database adapter
+    def database_adapter(name = :default)
+      @databases[name] || @databases[:default]
     end
   end
 

lib/scenic/definition.rb

@@ -1,9 +1,10 @@
 module Scenic
   # @api private
   class Definition
-    def initialize(name, version)
+    def initialize(name, version, database = nil)
       @name = name.to_s
       @version = version.to_i
+      @database = database
     end
 
     def to_sql
@@ -19,7 +20,12 @@ def full_path
     end
 
     def path
-      File.join("db", "views", filename)
+      views_dir = if @database && @database != :default
+        "#{@database}_views"
+      else
+        "views"
+      end
+      File.join("db", views_dir, filename)
     end
 
     def version