Merge branch 'master' into activestorage-guide

32 files changed, 428 insertions, 66 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 217eada1d7..60ceffac5e 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,22 @@
+*   Don't allow scopes to be defined which conflict with instance methods on `Relation`.
+
+    Fixes #31120.
+
+    *kinnrot*
+
+
+## Rails 5.2.0.beta2 (November 28, 2017) ##
+
+*   No changes.
+
+
+## Rails 5.2.0.beta1 (November 27, 2017) ##
+
+*   Add new error class `QueryCanceled` which will be raised
+    when canceling statement due to user request.
+
+    *Ryuta Kamizono*
+
 *   Add `#up_only` to database migrations for code that is only relevant when
     migrating up, e.g. populating a new column.
 
@@ -190,7 +209,7 @@
 
     *Jeremy Green*
 
-*   Add new error class `TransactionTimeout` which will be raised
+*   Add new error class `LockWaitTimeout` which will be raised
     when lock wait timeout exceeded.
 
     *Gabriel Courtemanche*
diff --git a/activerecord/README.rdoc b/activerecord/README.rdoc
index ba83a9adb2..19650b82ae 100644
--- a/activerecord/README.rdoc
+++ b/activerecord/README.rdoc
@@ -208,7 +208,7 @@ API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/activerecord/lib/active_record/associations/collection_association.rb b/activerecord/lib/active_record/associations/collection_association.rb
index ed215fb22c..921237a735 100644
--- a/activerecord/lib/active_record/associations/collection_association.rb
+++ b/activerecord/lib/active_record/associations/collection_association.rb
@@ -79,7 +79,13 @@ module ActiveRecord
       def find(*args)
         if options[:inverse_of] && loaded?
           args_flatten = args.flatten
-          raise RecordNotFound, "Couldn't find #{scope.klass.name} without an ID" if args_flatten.blank?
+          model = scope.klass
+
+          if args_flatten.blank?
+            error_message = "Couldn't find #{model.name} without an ID"
+            raise RecordNotFound.new(error_message, model.name, model.primary_key, args)
+          end
+
           result = find_by_scan(*args)
 
           result_size = Array(result).size
diff --git a/activerecord/lib/active_record/autosave_association.rb b/activerecord/lib/active_record/autosave_association.rb
index 6974cf74f6..a1250c3835 100644
--- a/activerecord/lib/active_record/autosave_association.rb
+++ b/activerecord/lib/active_record/autosave_association.rb
@@ -436,6 +436,9 @@ module ActiveRecord
             if (autosave && record.changed_for_autosave?) || new_record? || record_changed?(reflection, record, key)
               unless reflection.through_reflection
                 record[reflection.foreign_key] = key
+                if inverse_reflection = reflection.inverse_of
+                  record.association(inverse_reflection.name).loaded!
+                end
               end
 
               saved = record.save(validate: !autosave)
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
index 6c06f67239..9849f9d5d7 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -63,15 +63,13 @@ module ActiveRecord
     # There are several connection-pooling-related options that you can add to
     # your database connection configuration:
     #
-    # * +pool+: number indicating size of connection pool (default 5)
-    # * +checkout_timeout+: number of seconds to block and wait for a connection
-    #   before giving up and raising a timeout error (default 5 seconds).
-    # * +reaping_frequency+: frequency in seconds to periodically run the
-    #   Reaper, which attempts to find and recover connections from dead
-    #   threads, which can occur if a programmer forgets to close a
-    #   connection at the end of a thread or a thread dies unexpectedly.
-    #   Regardless of this setting, the Reaper will be invoked before every
-    #   blocking wait. (Default +nil+, which means don't schedule the Reaper).
+    # * +pool+: maximum number of connections the pool may manage (default 5).
+    # * +idle_timeout+: number of seconds that a connection will be kept
+    #   unused in the pool before it is automatically disconnected (default
+    #   300 seconds). Set this to zero to keep connections forever.
+    # * +checkout_timeout+: number of seconds to wait for a connection to
+    #   become available before giving up and raising a timeout error (default
+    #   5 seconds).
     #
     #--
     # Synchronization policy:
@@ -280,12 +278,12 @@ module ActiveRecord
           end
       end
 
-      # Every +frequency+ seconds, the reaper will call +reap+ on +pool+.
-      # A reaper instantiated with a +nil+ frequency will never reap the
-      # connection pool.
+      # Every +frequency+ seconds, the reaper will call +reap+ and +flush+ on
+      # +pool+. A reaper instantiated with a zero frequency will never reap
+      # the connection pool.
       #
-      # Configure the frequency by setting "reaping_frequency" in your
-      # database yaml file.
+      # Configure the frequency by setting +reaping_frequency+ in your database
+      # yaml file (default 60 seconds).
       class Reaper
         attr_reader :pool, :frequency
 
@@ -295,11 +293,12 @@ module ActiveRecord
         end
 
         def run
-          return unless frequency
+          return unless frequency && frequency > 0
           Thread.new(frequency, pool) { |t, p|
             loop do
               sleep t
               p.reap
+              p.flush
             end
           }
         end
@@ -323,6 +322,10 @@ module ActiveRecord
         @spec = spec
 
         @checkout_timeout = (spec.config[:checkout_timeout] && spec.config[:checkout_timeout].to_f) || 5
+        if @idle_timeout = spec.config.fetch(:idle_timeout, 300)
+          @idle_timeout = @idle_timeout.to_f
+          @idle_timeout = nil if @idle_timeout <= 0
+        end
 
         # default max pool size to 5
         @size = (spec.config[:pool] && spec.config[:pool].to_i) || 5
@@ -353,7 +356,10 @@ module ActiveRecord
 
         @lock_thread = false
 
-        @reaper = Reaper.new(self, spec.config[:reaping_frequency] && spec.config[:reaping_frequency].to_f)
+        # +reaping_frequency+ is configurable mostly for historical reasons, but it could
+        # also be useful if someone wants a very low +idle_timeout+.
+        reaping_frequency = spec.config.fetch(:reaping_frequency, 60)
+        @reaper = Reaper.new(self, reaping_frequency && reaping_frequency.to_f)
         @reaper.run
       end
 
@@ -447,6 +453,21 @@ module ActiveRecord
         disconnect(false)
       end
 
+      # Discards all connections in the pool (even if they're currently
+      # leased!), along with the pool itself. Any further interaction with the
+      # pool (except #spec and #schema_cache) is undefined.
+      #
+      # See AbstractAdapter#discard!
+      def discard! # :nodoc:
+        synchronize do
+          return if @connections.nil? # already discarded
+          @connections.each do |conn|
+            conn.discard!
+          end
+          @connections = @available = @thread_cached_conns = nil
+        end
+      end
+
       # Clears the cache which maps classes and re-connects connections that
       # require reloading.
       #
@@ -572,6 +593,35 @@ module ActiveRecord
         end
       end
 
+      # Disconnect all connections that have been idle for at least
+      # +minimum_idle+ seconds. Connections currently checked out, or that were
+      # checked in less than +minimum_idle+ seconds ago, are unaffected.
+      def flush(minimum_idle = @idle_timeout)
+        return if minimum_idle.nil?
+
+        idle_connections = synchronize do
+          @connections.select do |conn|
+            !conn.in_use? && conn.seconds_idle >= minimum_idle
+          end.each do |conn|
+            conn.lease
+
+            @available.delete conn
+            @connections.delete conn
+          end
+        end
+
+        idle_connections.each do |conn|
+          conn.disconnect!
+        end
+      end
+
+      # Disconnect all currently idle connections. Connections currently checked
+      # out are unaffected.
+      def flush!
+        reap
+        flush(-1)
+      end
+
       def num_waiting_in_queue # :nodoc:
         @available.num_waiting
       end
@@ -863,11 +913,31 @@ module ActiveRecord
     # about the model. The model needs to pass a specification name to the handler,
     # in order to look up the correct connection pool.
     class ConnectionHandler
+      def self.unowned_pool_finalizer(pid_map) # :nodoc:
+        lambda do |_|
+          discard_unowned_pools(pid_map)
+        end
+      end
+
+      def self.discard_unowned_pools(pid_map) # :nodoc:
+        pid_map.each do |pid, pools|
+          pools.values.compact.each(&:discard!) unless pid == Process.pid
+        end
+      end
+
       def initialize
         # These caches are keyed by spec.name (ConnectionSpecification#name).
         @owner_to_pool = Concurrent::Map.new(initial_capacity: 2) do |h, k|
+          # Discard the parent's connection pools immediately; we have no need
+          # of them
+          ConnectionHandler.discard_unowned_pools(h)
+
           h[k] = Concurrent::Map.new(initial_capacity: 2)
         end
+
+        # Backup finalizer: if the forked child never needed a pool, the above
+        # early discard has not occurred
+        ObjectSpace.define_finalizer self, ConnectionHandler.unowned_pool_finalizer(@owner_to_pool)
       end
 
       def connection_pool_list
@@ -921,6 +991,13 @@ module ActiveRecord
         connection_pool_list.each(&:disconnect!)
       end
 
+      # Disconnects all currently idle connections.
+      #
+      # See ConnectionPool#flush! for details.
+      def flush_idle_connections!
+        connection_pool_list.each(&:flush!)
+      end
+
       # Locate the connection of the nearest super class. This can be an
       # active or defined connection: if it is the latter, it will be
       # opened and set as the active connection for the class it was defined
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 7e6db860dd..8993c517a6 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -105,6 +105,7 @@ module ActiveRecord
         @logger              = logger
         @config              = config
         @pool                = nil
+        @idle_since          = Concurrent.monotonic_time
         @schema_cache        = SchemaCache.new self
         @quoted_column_names, @quoted_table_names = {}, {}
         @visitor = arel_visitor
@@ -164,6 +165,7 @@ module ActiveRecord
               "Current thread: #{Thread.current}."
           end
 
+          @idle_since = Concurrent.monotonic_time
           @owner = nil
         else
           raise ActiveRecordError, "Cannot expire connection, it is not currently leased."
@@ -183,6 +185,12 @@ module ActiveRecord
         end
       end
 
+      # Seconds since this connection was returned to the pool
+      def seconds_idle # :nodoc:
+        return 0 if in_use?
+        Concurrent.monotonic_time - @idle_since
+      end
+
       def unprepared_statement
         old_prepared_statements, @prepared_statements = @prepared_statements, false
         yield
@@ -367,6 +375,19 @@ module ActiveRecord
         reset_transaction
       end
 
+      # Immediately forget this connection ever existed. Unlike disconnect!,
+      # this will not communicate with the server.
+      #
+      # After calling this method, the behavior of all other methods becomes
+      # undefined. This is called internally just before a forked process gets
+      # rid of a connection that belonged to its parent.
+      def discard!
+        # This should be overridden by concrete adapters.
+        #
+        # Prevent @connection's finalizer from touching the socket, or
+        # otherwise communicating with its server, when it is collected.
+      end
+
       # Reset the state of this connection, directing the DBMS to clear
       # transactions and other connection-related server-side state. Usually a
       # database-dependent operation.
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index ca651ef390..ede8a9c1e2 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -44,7 +44,7 @@ module ActiveRecord
         json:        { name: "json" },
       }
 
-      class StatementPool < ConnectionAdapters::StatementPool
+      class StatementPool < ConnectionAdapters::StatementPool # :nodoc:
         private def dealloc(stmt)
           stmt[:stmt].close
         end
@@ -635,6 +635,7 @@ module ActiveRecord
         ER_CANNOT_ADD_FOREIGN   = 1215
         ER_CANNOT_CREATE_TABLE  = 1005
         ER_LOCK_WAIT_TIMEOUT    = 1205
+        ER_QUERY_INTERRUPTED    = 1317
         ER_QUERY_TIMEOUT        = 3024
 
         def translate_exception(exception, message)
@@ -660,9 +661,11 @@ module ActiveRecord
           when ER_LOCK_DEADLOCK
             Deadlocked.new(message)
           when ER_LOCK_WAIT_TIMEOUT
-            TransactionTimeout.new(message)
+            LockWaitTimeout.new(message)
           when ER_QUERY_TIMEOUT
             StatementTimeout.new(message)
+          when ER_QUERY_INTERRUPTED
+            QueryCanceled.new(message)
           else
             super
           end
diff --git a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
index 8de582fee1..bfdc7995f0 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
@@ -3,9 +3,8 @@
 require "active_record/connection_adapters/abstract_mysql_adapter"
 require "active_record/connection_adapters/mysql/database_statements"
 
-gem "mysql2", ">= 0.3.18", "< 0.5"
+gem "mysql2", "~> 0.4.4"
 require "mysql2"
-raise "mysql2 0.4.3 is not supported. Please upgrade to 0.4.4+" if Mysql2::VERSION == "0.4.3"
 
 module ActiveRecord
   module ConnectionHandling # :nodoc:
@@ -105,6 +104,11 @@ module ActiveRecord
         @connection.close
       end
 
+      def discard! # :nodoc:
+        @connection.automatic_close = false
+        @connection = nil
+      end
+
       private
 
         def connect
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 5ce6765dd8..27011bfe92 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -166,7 +166,7 @@ module ActiveRecord
         { concurrently: "CONCURRENTLY" }
       end
 
-      class StatementPool < ConnectionAdapters::StatementPool
+      class StatementPool < ConnectionAdapters::StatementPool # :nodoc:
         def initialize(connection, max)
           super(max)
           @connection = connection
@@ -182,7 +182,6 @@ module ActiveRecord
         end
 
         private
-
           def dealloc(key)
             @connection.query "DEALLOCATE #{key}" if connection_active?
           rescue PG::Error
@@ -273,6 +272,11 @@ module ActiveRecord
         end
       end
 
+      def discard! # :nodoc:
+        @connection.socket_io.reopen(IO::NULL)
+        @connection = nil
+      end
+
       def native_database_types #:nodoc:
         NATIVE_DATABASE_TYPES
       end
@@ -413,9 +417,9 @@ module ActiveRecord
           when DEADLOCK_DETECTED
             Deadlocked.new(message)
           when LOCK_NOT_AVAILABLE
-            TransactionTimeout.new(message)
+            LockWaitTimeout.new(message)
           when QUERY_CANCELED
-            StatementTimeout.new(message)
+            QueryCanceled.new(message)
           else
             super
           end
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 670afa3684..daece2bffd 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -90,9 +90,8 @@ module ActiveRecord
       #   Rails.application.config.active_record.sqlite3.represent_boolean_as_integer = true
       class_attribute :represent_boolean_as_integer, default: false
 
-      class StatementPool < ConnectionAdapters::StatementPool
+      class StatementPool < ConnectionAdapters::StatementPool # :nodoc:
         private
-
           def dealloc(stmt)
             stmt[:stmt].close unless stmt[:stmt].closed?
           end
diff --git a/activerecord/lib/active_record/connection_handling.rb b/activerecord/lib/active_record/connection_handling.rb
index 9a47edfba4..88d28dc52a 100644
--- a/activerecord/lib/active_record/connection_handling.rb
+++ b/activerecord/lib/active_record/connection_handling.rb
@@ -140,6 +140,6 @@ module ActiveRecord
     end
 
     delegate :clear_active_connections!, :clear_reloadable_connections!,
-      :clear_all_connections!, to: :connection_handler
+      :clear_all_connections!, :flush_idle_connections!, to: :connection_handler
   end
 end
diff --git a/activerecord/lib/active_record/enum.rb b/activerecord/lib/active_record/enum.rb
index f373b98035..1a3e6e4d09 100644
--- a/activerecord/lib/active_record/enum.rb
+++ b/activerecord/lib/active_record/enum.rb
@@ -221,6 +221,8 @@ module ActiveRecord
       def detect_enum_conflict!(enum_name, method_name, klass_method = false)
         if klass_method && dangerous_class_method?(method_name)
           raise_conflict_error(enum_name, method_name, type: "class")
+        elsif klass_method && method_defined_within?(method_name, Relation)
+          raise_conflict_error(enum_name, method_name, type: "class", source: Relation.name)
         elsif !klass_method && dangerous_attribute_method?(method_name)
           raise_conflict_error(enum_name, method_name)
         elsif !klass_method && method_defined_within?(method_name, _enum_methods_module, Module)
diff --git a/activerecord/lib/active_record/errors.rb b/activerecord/lib/active_record/errors.rb
index 7382879fce..efcbd44776 100644
--- a/activerecord/lib/active_record/errors.rb
+++ b/activerecord/lib/active_record/errors.rb
@@ -335,14 +335,18 @@ module ActiveRecord
   class IrreversibleOrderError < ActiveRecordError
   end
 
-  # TransactionTimeout will be raised when lock wait timeout exceeded.
-  class TransactionTimeout < StatementInvalid
+  # LockWaitTimeout will be raised when lock wait timeout exceeded.
+  class LockWaitTimeout < StatementInvalid
   end
 
   # StatementTimeout will be raised when statement timeout exceeded.
   class StatementTimeout < StatementInvalid
   end
 
+  # QueryCanceled will be raised when canceling statement due to user request.
+  class QueryCanceled < StatementInvalid
+  end
+
   # UnknownAttributeReference is raised when an unknown and potentially unsafe
   # value is passed to a query method when allow_unsafe_raw_sql is set to
   # :disabled. For example, passing a non column name value to a relation's
diff --git a/activerecord/lib/active_record/gem_version.rb b/activerecord/lib/active_record/gem_version.rb
index 7ccb57b305..7e47dac016 100644
--- a/activerecord/lib/active_record/gem_version.rb
+++ b/activerecord/lib/active_record/gem_version.rb
@@ -10,7 +10,7 @@ module ActiveRecord
     MAJOR = 5
     MINOR = 2
     TINY  = 0
-    PRE   = "alpha"
+    PRE   = "beta2"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index 360bf25a8c..15e9c09ffb 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -737,8 +737,8 @@ module ActiveRecord
     # Used to specify an operation that is only run when migrating up
     # (for example, populating a new column with its initial values).
     #
-    # In the following example, the new column `published` will be given
-    # the value `true` for all existing records.
+    # In the following example, the new column +published+ will be given
+    # the value +true+ for all existing records.
     #
     #    class AddPublishedToPosts < ActiveRecord::Migration[5.2]
     #      def change
diff --git a/activerecord/lib/active_record/migration/command_recorder.rb b/activerecord/lib/active_record/migration/command_recorder.rb
index ac7d506fd1..81ef4828f8 100644
--- a/activerecord/lib/active_record/migration/command_recorder.rb
+++ b/activerecord/lib/active_record/migration/command_recorder.rb
@@ -110,7 +110,7 @@ module ActiveRecord
 
       private
 
-        module StraightReversions
+        module StraightReversions # :nodoc:
           private
             { transaction:       :transaction,
               execute_block:     :execute_block,
diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index 12ee4a4137..1941d3d5ea 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -323,11 +323,11 @@ module ActiveRecord
       end
 
       def attributes_builder # :nodoc:
-        @attributes_builder ||= ActiveModel::AttributeSet::Builder.new(attribute_types, primary_key) do |name|
-          unless columns_hash.key?(name)
-            _default_attributes[name].dup
-          end
+        unless defined?(@attributes_builder) && @attributes_builder
+          defaults = _default_attributes.except(*(column_names - [primary_key]))
+          @attributes_builder = ActiveModel::AttributeSet::Builder.new(attribute_types, defaults)
         end
+        @attributes_builder
       end
 
       def columns_hash # :nodoc:
diff --git a/activerecord/lib/active_record/railtie.rb b/activerecord/lib/active_record/railtie.rb
index 812e1d7a00..9ee8425e1b 100644
--- a/activerecord/lib/active_record/railtie.rb
+++ b/activerecord/lib/active_record/railtie.rb
@@ -177,7 +177,16 @@ end_warning
     initializer "active_record.clear_active_connections" do
       config.after_initialize do
         ActiveSupport.on_load(:active_record) do
+          # Ideally the application doesn't connect to the database during boot,
+          # but sometimes it does. In case it did, we want to empty out the
+          # connection pools so that a non-database-using process (e.g. a master
+          # process in a forking server model) doesn't retain a needless
+          # connection. If it was needed, the incremental cost of reestablishing
+          # this connection is trivial: the rest of the pool would need to be
+          # populated anyway.
+
           clear_active_connections!
+          flush_idle_connections!
         end
       end
     end
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index 706fd57704..ff06ecbee1 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -18,9 +18,10 @@ module ActiveRecord
     #   Person.find([1])        # returns an array for the object with ID = 1
     #   Person.where("administrator = 1").order("created_on DESC").find(1)
     #
-    # NOTE: The returned records may not be in the same order as the ids you
-    # provide since database rows are unordered. You will need to provide an explicit QueryMethods#order
-    # option if you want the results to be sorted.
+    # NOTE: The returned records are in the same order as the ids you provide.
+    # If you want the results to be sorted by database, you can use ActiveRecord::QueryMethods#where
+    # method and provide an explicit ActiveRecord::QueryMethods#order option.
+    # But ActiveRecord::QueryMethods#where method doesn't raise ActiveRecord::RecordNotFound.
     #
     # ==== Find with lock
     #
@@ -88,7 +89,7 @@ module ActiveRecord
       where(arg, *args).take!
     rescue ::RangeError
       raise RecordNotFound.new("Couldn't find #{@klass.name} with an out of range value",
-                               @klass.name)
+                               @klass.name, @klass.primary_key)
     end
 
     # Gives a record (or N records if a parameter is supplied) without any implied
@@ -339,7 +340,7 @@ module ActiveRecord
       if ids.nil?
         error = "Couldn't find #{name}".dup
         error << " with#{conditions}" if conditions
-        raise RecordNotFound.new(error, name)
+        raise RecordNotFound.new(error, name, key)
       elsif Array(ids).size == 1
         error = "Couldn't find #{name} with '#{key}'=#{ids}#{conditions}"
         raise RecordNotFound.new(error, name, key, ids)
@@ -347,7 +348,7 @@ module ActiveRecord
         error = "Couldn't find all #{name.pluralize} with '#{key}': ".dup
         error << "(#{ids.join(", ")})#{conditions} (found #{result_size} results, but was looking for #{expected_size})."
         error << " Couldn't find #{name.pluralize(not_found_ids.size)} with #{key.to_s.pluralize(not_found_ids.size)} #{not_found_ids.join(', ')}." if not_found_ids
-        raise RecordNotFound.new(error, name, primary_key, ids)
+        raise RecordNotFound.new(error, name, key, ids)
       end
     end
 
@@ -433,9 +434,12 @@ module ActiveRecord
 
         ids = ids.flatten.compact.uniq
 
+        model_name = @klass.name
+
         case ids.size
         when 0
-          raise RecordNotFound, "Couldn't find #{@klass.name} without an ID"
+          error_message = "Couldn't find #{model_name} without an ID"
+          raise RecordNotFound.new(error_message, model_name, primary_key)
         when 1
           result = find_one(ids.first)
           expects_array ? [ result ] : result
@@ -443,7 +447,8 @@ module ActiveRecord
           find_some(ids)
         end
       rescue ::RangeError
-        raise RecordNotFound, "Couldn't find #{@klass.name} with an out of range ID"
+        error_message = "Couldn't find #{model_name} with an out of range ID"
+        raise RecordNotFound.new(error_message, model_name, primary_key, ids)
       end
 
       def find_one(id)
diff --git a/activerecord/lib/active_record/scoping.rb b/activerecord/lib/active_record/scoping.rb
index da585a9562..01ac56570a 100644
--- a/activerecord/lib/active_record/scoping.rb
+++ b/activerecord/lib/active_record/scoping.rb
@@ -11,23 +11,23 @@ module ActiveRecord
       include Named
     end
 
-    module ClassMethods
-      def current_scope(skip_inherited_scope = false) # :nodoc:
+    module ClassMethods # :nodoc:
+      def current_scope(skip_inherited_scope = false)
         ScopeRegistry.value_for(:current_scope, self, skip_inherited_scope)
       end
 
-      def current_scope=(scope) #:nodoc:
+      def current_scope=(scope)
         ScopeRegistry.set_value_for(:current_scope, self, scope)
       end
 
       # Collects attributes from scopes that should be applied when creating
       # an AR instance for the particular class this is called on.
-      def scope_attributes # :nodoc:
+      def scope_attributes
         all.scope_for_create
       end
 
       # Are there attributes associated with this scope?
-      def scope_attributes? # :nodoc:
+      def scope_attributes?
         current_scope
       end
     end
diff --git a/activerecord/lib/active_record/scoping/named.rb b/activerecord/lib/active_record/scoping/named.rb
index 310af72c41..752655aa05 100644
--- a/activerecord/lib/active_record/scoping/named.rb
+++ b/activerecord/lib/active_record/scoping/named.rb
@@ -171,6 +171,12 @@ module ActiveRecord
               "a class method with the same name."
           end
 
+          if method_defined_within?(name, Relation)
+            raise ArgumentError, "You tried to define a scope named \"#{name}\" " \
+              "on the model \"#{self.name}\", but ActiveRecord::Relation already defined " \
+              "an instance method with the same name."
+          end
+
           valid_scope_name?(name)
           extension = Module.new(&block) if block
 
diff --git a/activerecord/test/cases/adapters/mysql2/transaction_test.rb b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
index 4a3a4503de..cb183cc54c 100644
--- a/activerecord/test/cases/adapters/mysql2/transaction_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
@@ -60,8 +60,8 @@ module ActiveRecord
       end
     end
 
-    test "raises TransactionTimeout when lock wait timeout exceeded" do
-      assert_raises(ActiveRecord::TransactionTimeout) do
+    test "raises LockWaitTimeout when lock wait timeout exceeded" do
+      assert_raises(ActiveRecord::LockWaitTimeout) do
         s = Sample.create!(value: 1)
         latch1 = Concurrent::CountDownLatch.new
         latch2 = Concurrent::CountDownLatch.new
@@ -116,5 +116,32 @@ module ActiveRecord
         end
       end
     end
+
+    test "raises QueryCanceled when canceling statement due to user request" do
+      assert_raises(ActiveRecord::QueryCanceled) do
+        s = Sample.create!(value: 1)
+        latch = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch.count_down
+            sleep(0.5)
+            conn = Sample.connection
+            pid = conn.query_value("SELECT id FROM information_schema.processlist WHERE info LIKE '% FOR UPDATE'")
+            conn.execute("KILL QUERY #{pid}")
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch.wait
+            Sample.lock.find(s.id)
+          end
+        ensure
+          thread.join
+        end
+      end
+    end
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/transaction_test.rb b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
index 4d63bbce59..c24dfeb345 100644
--- a/activerecord/test/cases/adapters/postgresql/transaction_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
@@ -91,9 +91,9 @@ module ActiveRecord
       end
     end
 
-    test "raises TransactionTimeout when lock wait timeout exceeded" do
+    test "raises LockWaitTimeout when lock wait timeout exceeded" do
       skip unless ActiveRecord::Base.connection.postgresql_version >= 90300
-      assert_raises(ActiveRecord::TransactionTimeout) do
+      assert_raises(ActiveRecord::LockWaitTimeout) do
         s = Sample.create!(value: 1)
         latch1 = Concurrent::CountDownLatch.new
         latch2 = Concurrent::CountDownLatch.new
@@ -120,8 +120,8 @@ module ActiveRecord
       end
     end
 
-    test "raises StatementTimeout when statement timeout exceeded" do
-      assert_raises(ActiveRecord::StatementTimeout) do
+    test "raises QueryCanceled when statement timeout exceeded" do
+      assert_raises(ActiveRecord::QueryCanceled) do
         s = Sample.create!(value: 1)
         latch1 = Concurrent::CountDownLatch.new
         latch2 = Concurrent::CountDownLatch.new
@@ -148,6 +148,33 @@ module ActiveRecord
       end
     end
 
+    test "raises QueryCanceled when canceling statement due to user request" do
+      assert_raises(ActiveRecord::QueryCanceled) do
+        s = Sample.create!(value: 1)
+        latch = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch.count_down
+            sleep(0.5)
+            conn = Sample.connection
+            pid = conn.query_value("SELECT pid FROM pg_stat_activity WHERE query LIKE '% FOR UPDATE'")
+            conn.execute("SELECT pg_cancel_backend(#{pid})")
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch.wait
+            Sample.lock.find(s.id)
+          end
+        ensure
+          thread.join
+        end
+      end
+    end
+
     private
 
       def with_warning_suppression
diff --git a/activerecord/test/cases/associations/inverse_associations_test.rb b/activerecord/test/cases/associations/inverse_associations_test.rb
index e13cf93dcf..c0d328ca8a 100644
--- a/activerecord/test/cases/associations/inverse_associations_test.rb
+++ b/activerecord/test/cases/associations/inverse_associations_test.rb
@@ -484,7 +484,10 @@ class InverseHasManyTests < ActiveRecord::TestCase
   def test_raise_record_not_found_error_when_no_ids_are_passed
     man = Man.create!
 
-    assert_raise(ActiveRecord::RecordNotFound) { man.interests.find() }
+    exception = assert_raise(ActiveRecord::RecordNotFound) { man.interests.load.find() }
+
+    assert_equal exception.model, "Interest"
+    assert_equal exception.primary_key, "id"
   end
 
   def test_trying_to_use_inverses_that_dont_exist_should_raise_an_error
@@ -672,6 +675,16 @@ class InversePolymorphicBelongsToTests < ActiveRecord::TestCase
     assert_equal old_inversed_man.object_id, new_inversed_man.object_id
   end
 
+  def test_inversed_instance_should_not_be_reloaded_after_stale_state_changed_with_validation
+    face = Face.new man: Man.new
+
+    old_inversed_man = face.man
+    face.save!
+    new_inversed_man = face.man
+
+    assert_equal old_inversed_man.object_id, new_inversed_man.object_id
+  end
+
   def test_should_not_try_to_set_inverse_instances_when_the_inverse_is_a_has_many
     i = interests(:llama_wrangling)
     m = i.polymorphic_man
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 2f42684212..c48f7d3518 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -200,12 +200,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   if current_adapter?(:Mysql2Adapter)
     test "read attributes_before_type_cast on a boolean" do
       bool = Boolean.create!("value" => false)
-      if RUBY_PLATFORM.include?("java")
-        # JRuby will return the value before typecast as string.
-        assert_equal "0", bool.reload.attributes_before_type_cast["value"]
-      else
-        assert_equal 0, bool.reload.attributes_before_type_cast["value"]
-      end
+      assert_equal 0, bool.reload.attributes_before_type_cast["value"]
     end
   end
 
diff --git a/activerecord/test/cases/connection_adapters/connection_handler_test.rb b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
index 74d0ed348e..cae74a2b9b 100644
--- a/activerecord/test/cases/connection_adapters/connection_handler_test.rb
+++ b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
@@ -1,10 +1,15 @@
 # frozen_string_literal: true
 
 require "cases/helper"
+require "models/person"
 
 module ActiveRecord
   module ConnectionAdapters
     class ConnectionHandlerTest < ActiveRecord::TestCase
+      self.use_transactional_tests = false
+
+      fixtures :people
+
       def setup
         @handler = ConnectionHandler.new
         @spec_name = "primary"
@@ -139,6 +144,33 @@ module ActiveRecord
           rd.close
         end
 
+        def test_forked_child_doesnt_mangle_parent_connection
+          object_id = ActiveRecord::Base.connection.object_id
+          assert ActiveRecord::Base.connection.active?
+
+          rd, wr = IO.pipe
+          rd.binmode
+          wr.binmode
+
+          pid = fork {
+            rd.close
+            if ActiveRecord::Base.connection.active?
+              wr.write Marshal.dump ActiveRecord::Base.connection.object_id
+            end
+            wr.close
+
+            exit # allow finalizers to run
+          }
+
+          wr.close
+
+          Process.waitpid pid
+          assert_not_equal object_id, Marshal.load(rd.read)
+          rd.close
+
+          assert_equal 3, ActiveRecord::Base.connection.select_value("SELECT COUNT(*) FROM people")
+        end
+
         def test_retrieve_connection_pool_copies_schema_cache_from_ancestor_pool
           @pool.schema_cache = @pool.connection.schema_cache
           @pool.schema_cache.add("posts")
diff --git a/activerecord/test/cases/connection_pool_test.rb b/activerecord/test/cases/connection_pool_test.rb
index cb2fefb4f6..1e08cc74dc 100644
--- a/activerecord/test/cases/connection_pool_test.rb
+++ b/activerecord/test/cases/connection_pool_test.rb
@@ -156,6 +156,53 @@ module ActiveRecord
         @pool.connections.each { |conn| conn.close if conn.in_use? }
       end
 
+      def test_flush
+        idle_conn = @pool.checkout
+        recent_conn = @pool.checkout
+        active_conn = @pool.checkout
+
+        @pool.checkin idle_conn
+        @pool.checkin recent_conn
+
+        assert_equal 3, @pool.connections.length
+
+        def idle_conn.seconds_idle
+          1000
+        end
+
+        @pool.flush(30)
+
+        assert_equal 2, @pool.connections.length
+
+        assert_equal [recent_conn, active_conn].sort_by(&:__id__), @pool.connections.sort_by(&:__id__)
+      ensure
+        @pool.checkin active_conn
+      end
+
+      def test_flush_bang
+        idle_conn = @pool.checkout
+        recent_conn = @pool.checkout
+        active_conn = @pool.checkout
+        _dead_conn = Thread.new { @pool.checkout }.join
+
+        @pool.checkin idle_conn
+        @pool.checkin recent_conn
+
+        assert_equal 4, @pool.connections.length
+
+        def idle_conn.seconds_idle
+          1000
+        end
+
+        @pool.flush!
+
+        assert_equal 1, @pool.connections.length
+
+        assert_equal [active_conn].sort_by(&:__id__), @pool.connections.sort_by(&:__id__)
+      ensure
+        @pool.checkin active_conn
+      end
+
       def test_remove_connection
         conn = @pool.checkout
         assert conn.in_use?
diff --git a/activerecord/test/cases/enum_test.rb b/activerecord/test/cases/enum_test.rb
index 78cb89ccc5..7cda712112 100644
--- a/activerecord/test/cases/enum_test.rb
+++ b/activerecord/test/cases/enum_test.rb
@@ -308,6 +308,24 @@ class EnumTest < ActiveRecord::TestCase
     end
   end
 
+  test "reserved enum values for relation" do
+    relation_method_samples = [
+      :records,
+      :to_ary,
+      :scope_for_create
+    ]
+
+    relation_method_samples.each do |value|
+      e = assert_raises(ArgumentError, "enum value `#{value}` should not be allowed") do
+        Class.new(ActiveRecord::Base) do
+          self.table_name = "books"
+          enum category: [:other, value]
+        end
+      end
+      assert_match(/You tried to define an enum named .* on the model/, e.message)
+    end
+  end
+
   test "overriding enum method should not raise" do
     assert_nothing_raised do
       Class.new(ActiveRecord::Base) do
diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb
index 1268949ba9..e936c56ab8 100644
--- a/activerecord/test/cases/finder_test.rb
+++ b/activerecord/test/cases/finder_test.rb
@@ -120,6 +120,21 @@ class FinderTest < ActiveRecord::TestCase
     assert_equal "The Fourth Topic of the day", records[2].title
   end
 
+  def test_find_with_ids_with_no_id_passed
+    exception = assert_raises(ActiveRecord::RecordNotFound) { Topic.find }
+    assert_equal exception.model, "Topic"
+    assert_equal exception.primary_key, "id"
+  end
+
+  def test_find_with_ids_with_id_out_of_range
+    exception = assert_raises(ActiveRecord::RecordNotFound) do
+      Topic.find("9999999999999999999999999999999")
+    end
+
+    assert_equal exception.model, "Topic"
+    assert_equal exception.primary_key, "id"
+  end
+
   def test_find_passing_active_record_object_is_not_permitted
     assert_raises(ArgumentError) do
       Topic.find(Topic.last)
diff --git a/activerecord/test/cases/reaper_test.rb b/activerecord/test/cases/reaper_test.rb
index 49170abe6f..6c7727ab1b 100644
--- a/activerecord/test/cases/reaper_test.rb
+++ b/activerecord/test/cases/reaper_test.rb
@@ -18,6 +18,7 @@ module ActiveRecord
 
       class FakePool
         attr_reader :reaped
+        attr_reader :flushed
 
         def initialize
           @reaped = false
@@ -26,6 +27,10 @@ module ActiveRecord
         def reap
           @reaped = true
         end
+
+        def flush
+          @flushed = true
+        end
       end
 
       # A reaper with nil time should never reap connections
@@ -47,6 +52,7 @@ module ActiveRecord
           Thread.pass
         end
         assert fp.reaped
+        assert fp.flushed
       end
 
       def test_pool_has_reaper
diff --git a/activerecord/test/cases/scoping/named_scoping_test.rb b/activerecord/test/cases/scoping/named_scoping_test.rb
index b0431a4e34..17d3f27bb1 100644
--- a/activerecord/test/cases/scoping/named_scoping_test.rb
+++ b/activerecord/test/cases/scoping/named_scoping_test.rb
@@ -151,6 +151,22 @@ class NamedScopingTest < ActiveRecord::TestCase
     assert_equal "The scope body needs to be callable.", e.message
   end
 
+  def test_scopes_name_is_relation_method
+    conflicts = [
+      :records,
+      :to_ary,
+      :to_sql,
+      :explain
+    ]
+
+    conflicts.each do |name|
+      e = assert_raises ArgumentError do
+        Class.new(Post).class_eval { scope name, -> { where(approved: true) } }
+      end
+      assert_match(/You tried to define a scope named \"#{name}\" on the model/, e.message)
+    end
+  end
+
   def test_active_records_have_scope_named__all__
     assert !Topic.all.empty?
 
diff --git a/activerecord/test/models/face.rb b/activerecord/test/models/face.rb
index 796aaa4dc9..948435136d 100644
--- a/activerecord/test/models/face.rb
+++ b/activerecord/test/models/face.rb
@@ -8,4 +8,8 @@ class Face < ActiveRecord::Base
   # These is a "broken" inverse_of for the purposes of testing
   belongs_to :horrible_man, class_name: "Man", inverse_of: :horrible_face
   belongs_to :horrible_polymorphic_man, polymorphic: true, inverse_of: :horrible_polymorphic_face
+
+  validate do
+    man
+  end
 end