Allow `truncate` for SQLite3 adapter and add `rails db:seed:replant` (#34779)

* Add `ActiveRecord::Base.connection.truncate` for SQLite3 adapter.

SQLite doesn't support `TRUNCATE TABLE`, but SQLite3 adapter can support
`ActiveRecord::Base.connection.truncate` by using `DELETE FROM`.

`DELETE` without `WHERE` uses "The Truncate Optimization",
see https://www.sqlite.org/lang_delete.html.

* Add `rails db:seed:replant` that truncates database tables and loads the seeds

Closes #34765

9 files changed, 213 insertions, 0 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 979b48c654..04449a3ebc 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,12 @@
+*   Add `rails db:seed:replant` that truncates tables of each database
+    for current environment and loads the seeds.
+
+    *bogdanvlviv*, *DHH*
+
+*   Add `ActiveRecord::Base.connection.truncate` for SQLite3 adapter.
+
+    *bogdanvlviv*
+
 *   Deprecate mismatched collation comparison for uniqueness validator.
 
     Uniqueness validator will no longer enforce case sensitive comparison in Rails 6.1.
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 9f28fdf749..63e07932d9 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -154,6 +154,10 @@ module ActiveRecord
         @statements.clear
       end
 
+      def truncate(table_name, name = nil)
+        execute "DELETE FROM #{quote_table_name(table_name)}", name
+      end
+
       def supports_index_sort_order?
         true
       end
diff --git a/activerecord/lib/active_record/railties/databases.rake b/activerecord/lib/active_record/railties/databases.rake
index 8de06e8466..f021a8f6c4 100644
--- a/activerecord/lib/active_record/railties/databases.rake
+++ b/activerecord/lib/active_record/railties/databases.rake
@@ -66,6 +66,11 @@ db_namespace = namespace :db do
     end
   end
 
+  # desc "Truncates tables of each database for current environment"
+  task truncate_all: [:load_config, :check_protected_environments] do
+    ActiveRecord::Tasks::DatabaseTasks.truncate_all
+  end
+
   # desc "Empty the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:purge:all to purge all databases in the config). Without RAILS_ENV it defaults to purging the development and test databases."
   task purge: [:load_config, :check_protected_environments] do
     ActiveRecord::Tasks::DatabaseTasks.purge_current
@@ -223,6 +228,11 @@ db_namespace = namespace :db do
     ActiveRecord::Tasks::DatabaseTasks.load_seed
   end
 
+  namespace :seed do
+    desc "Truncates tables of each database for current environment and loads the seeds"
+    task replant: [:load_config, :truncate_all, :seed]
+  end
+
   namespace :fixtures do
     desc "Loads fixtures into the current environment's database. Load specific fixtures using FIXTURES=x,y. Load from subdirectory in test/fixtures using FIXTURES_DIR=z. Specify an alternative path (eg. spec/fixtures) using FIXTURES_PATH=spec/fixtures."
     task load: :load_config do
diff --git a/activerecord/lib/active_record/tasks/database_tasks.rb b/activerecord/lib/active_record/tasks/database_tasks.rb
index 27e401a756..ef02ca8190 100644
--- a/activerecord/lib/active_record/tasks/database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/database_tasks.rb
@@ -182,6 +182,24 @@ module ActiveRecord
         }
       end
 
+      def truncate_tables(configuration)
+        ActiveRecord::Base.connected_to(database: { truncation: configuration }) do
+          table_names = ActiveRecord::Base.connection.tables
+          internal_table_names = [
+            ActiveRecord::Base.schema_migrations_table_name,
+            ActiveRecord::Base.internal_metadata_table_name
+          ]
+
+          class_for_adapter(configuration["adapter"]).new(configuration).truncate_tables(*table_names.without(*internal_table_names))
+        end
+      end
+
+      def truncate_all(environment = env)
+        ActiveRecord::Base.configurations.configs_for(env_name: environment).each do |db_config|
+          truncate_tables db_config.config
+        end
+      end
+
       def migrate
         check_target_version
 
diff --git a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
index 1c1b29b5e1..f2b4ead98d 100644
--- a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
@@ -31,6 +31,16 @@ module ActiveRecord
         connection.recreate_database configuration["database"], creation_options
       end
 
+      def truncate_tables(*table_names)
+        return if table_names.empty?
+
+        ActiveRecord::Base.connection.disable_referential_integrity do
+          table_names.each do |table_name|
+            ActiveRecord::Base.connection.truncate(table_name)
+          end
+        end
+      end
+
       def charset
         connection.charset
       end
diff --git a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
index 8acb11f75f..dc368eb97d 100644
--- a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
@@ -48,6 +48,18 @@ module ActiveRecord
         create true
       end
 
+      def truncate_tables(*table_names)
+        return if table_names.empty?
+
+        ActiveRecord::Base.connection.disable_referential_integrity do
+          quoted_table_names = table_names.map do |table_name|
+            ActiveRecord::Base.connection.quote_table_name(table_name)
+          end
+
+          ActiveRecord::Base.connection.execute "TRUNCATE TABLE #{quoted_table_names.join(", ")}"
+        end
+      end
+
       def structure_dump(filename, extra_flags)
         set_psql_env
 
diff --git a/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb b/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
index a82cea80ca..cedbae6b7f 100644
--- a/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
@@ -33,6 +33,16 @@ module ActiveRecord
         create
       end
 
+      def truncate_tables(*table_names)
+        return if table_names.empty?
+
+        ActiveRecord::Base.connection.disable_referential_integrity do
+          table_names.each do |table_name|
+            ActiveRecord::Base.connection.truncate(table_name)
+          end
+        end
+      end
+
       def charset
         connection.encoding
       end
diff --git a/activerecord/test/cases/adapters/sqlite3/connection_test.rb b/activerecord/test/cases/adapters/sqlite3/connection_test.rb
new file mode 100644
index 0000000000..3dabc8766a
--- /dev/null
+++ b/activerecord/test/cases/adapters/sqlite3/connection_test.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+
+class SQLite3ConnectionTest < ActiveRecord::SQLite3TestCase
+  fixtures :comments
+
+  def test_truncate
+    rows = ActiveRecord::Base.connection.exec_query("select count(*) from comments")
+    count = rows.first.values.first
+    assert_operator count, :>, 0
+
+    ActiveRecord::Base.connection.truncate("comments")
+    rows = ActiveRecord::Base.connection.exec_query("select count(*) from comments")
+    count = rows.first.values.first
+    assert_equal 0, count
+  end
+end
diff --git a/activerecord/test/cases/tasks/database_tasks_test.rb b/activerecord/test/cases/tasks/database_tasks_test.rb
index 3fd1813d64..bd6fb099a4 100644
--- a/activerecord/test/cases/tasks/database_tasks_test.rb
+++ b/activerecord/test/cases/tasks/database_tasks_test.rb
@@ -2,6 +2,7 @@
 
 require "cases/helper"
 require "active_record/tasks/database_tasks"
+require "models/author"
 
 module ActiveRecord
   module DatabaseTasksSetupper
@@ -944,6 +945,127 @@ module ActiveRecord
     end
   end
 
+  unless in_memory_db?
+    class DatabaseTasksTruncateAllTest < ActiveRecord::TestCase
+      self.use_transactional_tests = false
+
+      fixtures :authors, :author_addresses
+
+      def test_truncate_tables
+        assert_operator Author.count, :>, 0
+        assert_operator AuthorAddress.count, :>, 0
+
+        old_configurations = ActiveRecord::Base.configurations
+        configurations = { development: ActiveRecord::Base.configurations["arunit"] }
+        ActiveRecord::Base.configurations = configurations
+
+        ActiveRecord::Tasks::DatabaseTasks.stub(:root, nil) do
+          ActiveRecord::Tasks::DatabaseTasks.truncate_all(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+
+        assert_equal 0, Author.count
+        assert_equal 0, AuthorAddress.count
+      ensure
+        ActiveRecord::Base.configurations = old_configurations
+      end
+    end
+  end
+
+  class DatabaseTasksTruncateAllWithMultipleDatabasesTest < ActiveRecord::TestCase
+    def setup
+      @configurations = {
+        "development" => { "primary" => { "database" => "dev-db" }, "secondary" => { "database" => "secondary-dev-db" } },
+        "test" => { "primary" => { "database" => "test-db" }, "secondary" => { "database" => "secondary-test-db" } },
+        "production" => { "primary" => { "url" => "abstract://prod-db-host/prod-db" }, "secondary" => { "url" => "abstract://secondary-prod-db-host/secondary-prod-db" } }
+      }
+    end
+
+    def test_truncate_all_databases_for_environment
+      with_stubbed_configurations do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :truncate_tables,
+          [
+            ["database" => "test-db"],
+            ["database" => "secondary-test-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.truncate_all(
+            ActiveSupport::StringInquirer.new("test")
+          )
+        end
+      end
+    end
+
+    def test_truncate_all_databases_with_url_for_environment
+      with_stubbed_configurations do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :truncate_tables,
+          [
+            ["adapter" => "abstract", "database" => "prod-db", "host" => "prod-db-host"],
+            ["adapter" => "abstract", "database" => "secondary-prod-db", "host" => "secondary-prod-db-host"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.truncate_all(
+            ActiveSupport::StringInquirer.new("production")
+          )
+        end
+      end
+    end
+
+    def test_truncate_all_development_databases_when_env_was_no_specified
+      with_stubbed_configurations do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :truncate_tables,
+          [
+            ["database" => "dev-db"],
+            ["database" => "secondary-dev-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.truncate_all(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    end
+
+    def test_truncate_all_development_databases_when_env_is_development
+      old_env = ENV["RAILS_ENV"]
+      ENV["RAILS_ENV"] = "development"
+
+      with_stubbed_configurations do
+        assert_called_with(
+          ActiveRecord::Tasks::DatabaseTasks,
+          :truncate_tables,
+          [
+            ["database" => "dev-db"],
+            ["database" => "secondary-dev-db"]
+          ]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.truncate_all(
+            ActiveSupport::StringInquirer.new("development")
+          )
+        end
+      end
+    ensure
+      ENV["RAILS_ENV"] = old_env
+    end
+
+    private
+      def with_stubbed_configurations
+        old_configurations = ActiveRecord::Base.configurations
+        ActiveRecord::Base.configurations = @configurations
+
+        yield
+      ensure
+        ActiveRecord::Base.configurations = old_configurations
+      end
+  end
+
   class DatabaseTasksCharsetTest < ActiveRecord::TestCase
     include DatabaseTasksSetupper