Feat: Multiple database support

README.md

@@ -224,6 +224,126 @@ class UpdateSearchResultsToVersion2 < ActiveRecord::Migration
 end
 ```
 
+## Can I use Scenic with multiple databases?
+
+Yes! Scenic supports Rails' multiple database feature introduced in Rails 6.0.
+This allows you to manage views across different databases in your application.
+
+### Requirements
+
+- Rails 6.0 or higher
+- Multiple databases configured in your `database.yml`
+
+### Configuring Database Adapters
+
+If you need to customize the database adapter for a specific database, you can
+configure it in an initializer:
+
+```ruby
+# config/initializers/scenic.rb
+Scenic.configure do |config|
+  # The default database adapter is automatically configured
+  # config.database = Scenic::Adapters::Postgres.new
+
+  # Configure adapters for additional databases
+  config.databases[:secondary] = Scenic::Adapters::Postgres.new(SecondaryRecord)
+end
+```
+
+### Generating Views for Specific Databases
+
+Use the `--database` option to specify which database a view should be created in:
+
+```sh
+$ rails generate scenic:view analytics --database=secondary
+      create  db/views_secondary/analytics_v01.sql
+      create  db/migrate_secondary/[TIMESTAMP]_create_analytics.rb
+```
+
+This will:
+- Create the view definition in `db/views_secondary/` (instead of `db/views/`)
+- Create the migration in your database-specific migrations directory
+
+The migration will include the `database:` parameter:
+
+```ruby
+class CreateAnalytics < ActiveRecord::Migration[7.0]
+  def change
+    create_view :analytics, database: :secondary
+  end
+end
+```
+
+### Working with Multiple Database Views
+
+All Scenic methods (`create_view`, `update_view`, `replace_view`, `drop_view`)
+support the `database:` parameter:
+
+```ruby
+# In a migration
+def change
+  create_view :reports, version: 1, database: :secondary
+  update_view :analytics, version: 2, database: :secondary
+  drop_view :old_stats, database: :secondary
+end
+```
+
+### Running Migrations
+
+Use Rails' standard rake tasks for running migrations on specific databases:
+
+```sh
+$ rake db:migrate:secondary        # Run pending migrations
+$ rake db:rollback:secondary       # Rollback last migration
+```
+
+### Example: Multiple Database Setup
+
+Here's a complete example of using Scenic with multiple databases:
+
+```yaml
+# config/database.yml
+production:
+  primary:
+    <<: *default
+    database: my_app_production
+  analytics:
+    <<: *default
+    database: my_app_analytics
+    migrations_paths: db/migrate_analytics
+```
+
+```ruby
+# app/models/application_record.rb
+class ApplicationRecord < ActiveRecord::Base
+  self.abstract_class = true
+  connects_to database: { writing: :primary, reading: :primary }
+end
+
+# app/models/analytics_record.rb
+class AnalyticsRecord < ActiveRecord::Base
+  self.abstract_class = true
+  connects_to database: { writing: :analytics, reading: :analytics }
+end
+
+# app/models/user_activity_summary.rb
+class UserActivitySummary < AnalyticsRecord
+  # This view is defined in the analytics database
+  def readonly?
+    true
+  end
+end
+```
+
+Generate the view:
+
+```sh
+$ rails generate scenic:model user_activity_summary --database=analytics
+```
+
+The generated migration will automatically include `database: :analytics` and will
+be placed in your database-specific migrations directory.
+
 ## I don't need this view anymore. Make it go away.
 
 Scenic gives you `drop_view` too:
@@ -232,6 +352,7 @@ 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/model/model_generator.rb

@@ -8,6 +8,7 @@ module Generators
     # @api private
     class ModelGenerator < Rails::Generators::NamedBase
       include Scenic::Generators::Materializable
+
       source_root File.expand_path("templates", __dir__)
 
       def invoke_rails_model_generator

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

@@ -8,8 +8,13 @@ module Generators
     class ViewGenerator < Rails::Generators::NamedBase
       include Rails::Generators::Migration
       include Scenic::Generators::Materializable
+
       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)
@@ -28,12 +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
@@ -80,7 +85,26 @@ def file_name
       end
 
       def views_directory_path
-        @views_directory_path ||= Rails.root.join("db", "views")
+        @views_directory_path ||= if database && database != :default
+          Rails.root.join("db", "views_#{database}")
+        else
+          Rails.root.join("db", "views")
+        end
+      end
+
+      def migration_directory
+        if different_database_set?
+          db_config = ActiveRecord::Base.configurations.configs_for(
+            env_name: Rails.env,
+            name: database.to_s
+          )
+        end
+
+        db_config&.migrations_paths || "db/migrate"
+      end
+
+      def different_database_set?
+        database && database != :default
       end
 
       def version_regex
@@ -92,11 +116,11 @@ 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?
@@ -112,8 +136,21 @@ 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
+        "views_#{@database}"
+      else
+        "views"
+      end
+      File.join("db", views_dir, filename)
     end
 
     def version