Add option to disable schema dumb per-database

Dumping the schema is on by default for all databases in an application. To turn it off for a
specific database use the `schema_dump` option:

```yaml
  # config/database.yml

  production:
  schema_dump: false
```

Co-authored-by: Luis Vasconcellos <vasconcelloslf@gmail.com>

activerecord/CHANGELOG.md

@@ -1,3 +1,17 @@
+*   Add option to disable schema dumb per-database
+
+    Dumping the schema is on by default for all databases in an application. To turn it off for a
+    specific database use the `schema_dump` option:
+
+    ```yaml
+    # config/database.yml
+
+    production:
+      schema_dump: false
+    ```
+
+    *Luis Vasconcellos*, *Eileen M. Uchitelle*
+
 *   Fix `eager_loading?` when ordering with `Hash` syntax
 
     `eager_loading?` is triggered correctly when using `order` with hash syntax

activerecord/lib/active_record/database_configurations/hash_config.rb

@@ -26,6 +26,7 @@ module ActiveRecord
     #   connections.
     class HashConfig < DatabaseConfig
       attr_reader :configuration_hash
+
       def initialize(env_name, name, configuration_hash)
         super(env_name, name)
         @configuration_hash = configuration_hash.symbolize_keys.freeze
@@ -103,6 +104,11 @@ module ActiveRecord
       def schema_cache_path
         configuration_hash[:schema_cache_path]
       end
+
+      # Determines whether to dump the schema for a database.
+      def schema_dump
+        configuration_hash.fetch(:schema_dump, true)
+      end
     end
   end
 end

activerecord/lib/active_record/railties/databases.rake

@@ -121,9 +121,13 @@ db_namespace = namespace :db do
     ActiveRecord::Tasks::DatabaseTasks.for_each(databases) do |name|
       # IMPORTANT: This task won't dump the schema if ActiveRecord.dump_schema_after_migration is set to false
       task name do
-        if ActiveRecord.dump_schema_after_migration
+        db_config = ActiveRecord::Base.configurations.configs_for(env_name: ActiveRecord::Tasks::DatabaseTasks.env, name: name)
+
+        if ActiveRecord.dump_schema_after_migration && db_config.schema_dump
+          ActiveRecord::Base.establish_connection(db_config)
           db_namespace["schema:dump:#{name}"].invoke
         end
+
         # Allow this task to be called as many times as required. An example is the
         # migrate:redo task, which calls other two internally that depend on this one.
         db_namespace["_dump:#{name}"].reenable
@@ -433,9 +437,11 @@ db_namespace = namespace :db do
     desc "Creates a database schema file (either db/schema.rb or db/structure.sql, depending on `config.active_record.schema_format`)"
     task dump: :load_config do
       ActiveRecord::Base.configurations.configs_for(env_name: ActiveRecord::Tasks::DatabaseTasks.env).each do |db_config|
+        if db_config.schema_dump
           ActiveRecord::Base.establish_connection(db_config)
           ActiveRecord::Tasks::DatabaseTasks.dump_schema(db_config)
         end
+      end
 
       db_namespace["schema:dump"].reenable
     end

activerecord/test/cases/database_configurations/hash_config_test.rb

@@ -102,6 +102,26 @@ module ActiveRecord
         config = HashConfig.new("default_env", "primary", idle_timeout: "0")
         assert_nil config.idle_timeout
       end
+
+      def test_default_schema_dump_value
+        config = HashConfig.new("default_env", "primary", {})
+        assert_equal true, config.schema_dump
+      end
+
+      def test_schema_dump_value_set_to_true
+        config = HashConfig.new("default_env", "primary", { schema_dump: true })
+        assert_equal true, config.schema_dump
+      end
+
+      def test_schema_dump_value_set_to_nil
+        config = HashConfig.new("default_env", "primary", { schema_dump: nil })
+        assert_nil config.schema_dump
+      end
+
+      def test_schema_dump_value_set_to_false
+        config = HashConfig.new("default_env", "primary", { schema_dump: false })
+        assert_equal false, config.schema_dump
+      end
     end
   end
 end

railties/test/application/rake/migrations_test.rb

@@ -425,6 +425,42 @@ module ApplicationTests
         assert_match(/up\s+002\s+Two migration/, output)
       end
 
+      test "schema generation when dump_schema_after_migration and schema_dump are true" do
+        add_to_config("config.active_record.dump_schema_after_migration = true")
+
+        app_file "config/database.yml", <<~EOS
+          development:
+            adapter: sqlite3
+            database: 'dev_db'
+            schema_dump: true
+        EOS
+
+        Dir.chdir(app_path) do
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate"
+
+          assert File.exist?("db/schema.rb"), "should dump schema when configured to"
+        end
+      end
+
+      test "schema generation when dump_schema_after_migration is true schema_dump is false" do
+        add_to_config("config.active_record.dump_schema_after_migration = true")
+
+        app_file "config/database.yml", <<~EOS
+          development:
+            adapter: sqlite3
+            database: 'dev_db'
+            schema_dump: false
+        EOS
+
+        Dir.chdir(app_path) do
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate"
+
+          assert_not File.exist?("db/schema.rb"), "should not dump schema when configured not to"
+        end
+      end
+
       test "schema generation when dump_schema_after_migration is set" do
         add_to_config("config.active_record.dump_schema_after_migration = false")
 

railties/test/application/rake/multi_dbs_test.rb

@@ -812,6 +812,112 @@ module ApplicationTests
         db_create_and_drop_namespace("primary", "db/development.sqlite3")
       end
 
+      test "schema generation when dump_schema_after_migration is true schema_dump is false" do
+        app_file "config/database.yml", <<~EOS
+          development:
+            primary:
+              adapter: sqlite3
+              database: dev_db
+              schema_dump: false
+            secondary:
+              adapter: sqlite3
+              database: secondary_dev_db
+              schema_dump: false
+        EOS
+
+        Dir.chdir(app_path) do
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate"
+
+          assert_not File.exist?("db/schema.rb"), "should not dump schema when configured not to"
+          assert_not File.exist?("db/secondary_schema.rb"), "should not dump schema when configured not to"
+        end
+      end
+
+      test "schema generation when dump_schema_after_migration is false and schema_dump is true" do
+        add_to_config("config.active_record.dump_schema_after_migration = false")
+
+        app_file "config/database.yml", <<~EOS
+          development:
+            primary:
+              adapter: sqlite3
+              database: dev_db
+            secondary:
+              adapter: sqlite3
+              database: secondary_dev_db
+        EOS
+
+        Dir.chdir(app_path) do
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate"
+
+          assert_not File.exist?("db/schema.rb"), "should not dump schema when configured not to"
+          assert_not File.exist?("db/secondary_schema.rb"), "should not dump schema when configured not to"
+        end
+      end
+
+      test "schema generation with schema dump only for primary" do
+        app_file "config/database.yml", <<~EOS
+          development:
+            primary:
+              adapter: sqlite3
+              database: primary_dev_db
+            secondary:
+              adapter: sqlite3
+              database: secondary_dev_db
+              schema_dump: false
+        EOS
+
+        Dir.chdir(app_path) do
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate:primary", "db:migrate:secondary"
+
+          assert File.exist?("db/schema.rb"), "should not dump schema when configured not to"
+          assert_not File.exist?("db/secondary_schema.rb"), "should not dump schema when configured not to"
+        end
+      end
+
+      test "schema generation with schema dump only for secondary" do
+        app_file "config/database.yml", <<~EOS
+          development:
+            primary:
+              adapter: sqlite3
+              database: primary_dev_db
+              schema_dump: false
+            secondary:
+              adapter: sqlite3
+              database: secondary_dev_db
+        EOS
+
+        Dir.chdir(app_path) do
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate:primary", "db:migrate:secondary"
+
+          assert_not File.exist?("db/schema.rb"), "should not dump schema when configured not to"
+          assert File.exist?("db/secondary_schema.rb"), "should dump schema when configured to"
+        end
+      end
+
+      test "schema generation when dump_schema_after_migration and schema_dump are true" do
+        app_file "config/database.yml", <<~EOS
+          development:
+            primary:
+              adapter: sqlite3
+              database: dev_db
+            secondary:
+              adapter: sqlite3
+              database: secondary_dev_db
+        EOS
+
+        Dir.chdir(app_path) do
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate"
+
+          assert File.exist?("db/schema.rb"), "should dump schema when configured to"
+          assert File.exist?("db/secondary_schema.rb"), "should dump schema when configured to"
+        end
+      end
+
       test "db:create and db:drop don't raise errors when loading YAML containing multiple ERB statements on the same line" do
         app_file "config/database.yml", <<-YAML
           development: