Merge branch 'master' into bug/filtered_parameters_class

30 files changed, 486 insertions, 390 deletions

diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index 6efa448d49..e52c2004f3 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -1649,7 +1649,7 @@ module ActiveRecord
         #   you don't want to have association presence validated, use <tt>optional: true</tt>.
         # [:default]
         #   Provide a callable (i.e. proc or lambda) to specify that the association should
-        #   be initialized with a particular record before validation. 
+        #   be initialized with a particular record before validation.
         #
         # Option examples:
         #   belongs_to :firm, foreign_key: "client_of"
diff --git a/activerecord/lib/active_record/associations/collection_association.rb b/activerecord/lib/active_record/associations/collection_association.rb
index 77282e6463..62c944fce3 100644
--- a/activerecord/lib/active_record/associations/collection_association.rb
+++ b/activerecord/lib/active_record/associations/collection_association.rb
@@ -280,35 +280,6 @@ module ActiveRecord
         replace_on_target(record, index, skip_callbacks, &block)
       end
 
-      def replace_on_target(record, index, skip_callbacks)
-        callback(:before_add, record) unless skip_callbacks
-
-        begin
-          if index
-            record_was = target[index]
-            target[index] = record
-          else
-            target << record
-          end
-
-          set_inverse_instance(record)
-
-          yield(record) if block_given?
-        rescue
-          if index
-            target[index] = record_was
-          else
-            target.delete(record)
-          end
-
-          raise
-        end
-
-        callback(:after_add, record) unless skip_callbacks
-
-        record
-      end
-
       def scope
         scope = super
         scope.none! if null_scope?
@@ -385,15 +356,19 @@ module ActiveRecord
             transaction do
               add_to_target(build_record(attributes)) do |record|
                 yield(record) if block_given?
-                insert_record(record, true, raise)
+                insert_record(record, true, raise) { @_was_loaded = loaded? }
               end
             end
           end
         end
 
         # Do the relevant stuff to insert the given record into the association collection.
-        def insert_record(record, validate = true, raise = false)
-          raise NotImplementedError
+        def insert_record(record, validate = true, raise = false, &block)
+          if raise
+            record.save!(validate: validate, &block)
+          else
+            record.save(validate: validate, &block)
+          end
         end
 
         def create_scope
@@ -448,19 +423,41 @@ module ActiveRecord
           end
         end
 
-        def concat_records(records, should_raise = false)
+        def concat_records(records, raise = false)
           result = true
 
           records.each do |record|
             raise_on_type_mismatch!(record)
-            add_to_target(record) do |rec|
-              result &&= insert_record(rec, true, should_raise) unless owner.new_record?
+            add_to_target(record) do
+              result &&= insert_record(record, true, raise) { @_was_loaded = loaded? } unless owner.new_record?
             end
           end
 
           result && records
         end
 
+        def replace_on_target(record, index, skip_callbacks)
+          callback(:before_add, record) unless skip_callbacks
+
+          set_inverse_instance(record)
+
+          @_was_loaded = true
+
+          yield(record) if block_given?
+
+          if index
+            target[index] = record
+          elsif @_was_loaded || !loaded?
+            target << record
+          end
+
+          callback(:after_add, record) unless skip_callbacks
+
+          record
+        ensure
+          @_was_loaded = nil
+        end
+
         def callback(method, record)
           callbacks_for(method).each do |callback|
             callback.call(method, owner, record)
diff --git a/activerecord/lib/active_record/associations/has_many_association.rb b/activerecord/lib/active_record/associations/has_many_association.rb
index b413eb3f9c..10ca0e47ff 100644
--- a/activerecord/lib/active_record/associations/has_many_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_association.rb
@@ -31,12 +31,7 @@ module ActiveRecord
 
       def insert_record(record, validate = true, raise = false)
         set_owner_attributes(record)
-
-        if raise
-          record.save!(validate: validate)
-        else
-          record.save(validate: validate)
-        end
+        super
       end
 
       def empty?
diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index c4a7fe4432..53ffb3b68d 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -39,11 +39,7 @@ module ActiveRecord
         ensure_not_nested
 
         if record.new_record? || record.has_changes_to_save?
-          if raise
-            record.save!(validate: validate)
-          else
-            return unless record.save(validate: validate)
-          end
+          return unless super
         end
 
         save_through_record(record)
diff --git a/activerecord/lib/active_record/autosave_association.rb b/activerecord/lib/active_record/autosave_association.rb
index 6bccbc06cd..607c54e481 100644
--- a/activerecord/lib/active_record/autosave_association.rb
+++ b/activerecord/lib/active_record/autosave_association.rb
@@ -181,6 +181,7 @@ module ActiveRecord
 
           if reflection.collection?
             before_save :before_save_collection_association
+            after_save :after_save_collection_association
 
             define_non_cyclic_method(save_method) { save_collection_association(reflection) }
             # Doesn't use after_save as that would save associations added in after_create/after_update twice
@@ -371,6 +372,10 @@ module ActiveRecord
         true
       end
 
+      def after_save_collection_association
+        @new_record_before_save = false
+      end
+
       # Saves any new associated records, or all loaded autosave associations if
       # <tt>:autosave</tt> is enabled on the association.
       #
diff --git a/activerecord/lib/active_record/collection_cache_key.rb b/activerecord/lib/active_record/collection_cache_key.rb
index 43784b70e3..1e1de1863a 100644
--- a/activerecord/lib/active_record/collection_cache_key.rb
+++ b/activerecord/lib/active_record/collection_cache_key.rb
@@ -7,17 +7,27 @@ module ActiveRecord
       if collection.loaded?
         size = collection.size
         if size > 0
-          timestamp = collection.max_by(&timestamp_column).public_send(timestamp_column)
+          timestamp = collection.max_by(&timestamp_column)._read_attribute(timestamp_column)
         end
       else
         column_type = type_for_attribute(timestamp_column.to_s)
         column = "#{connection.quote_table_name(collection.table_name)}.#{connection.quote_column_name(timestamp_column)}"
+        select_values = "COUNT(*) AS #{connection.quote_column_name("size")}, MAX(%s) AS timestamp"
 
-        query = collection
-          .unscope(:select)
-          .select("COUNT(*) AS #{connection.quote_column_name("size")}", "MAX(#{column}) AS timestamp")
-          .unscope(:order)
-        result = connection.select_one(query)
+        if collection.limit_value || collection.offset_value
+          query = collection.spawn
+          query.select_values = [column]
+          subquery_alias = "subquery_for_cache_key"
+          subquery_column = "#{subquery_alias}.#{timestamp_column}"
+          subquery = query.arel.as(subquery_alias)
+          arel = Arel::SelectManager.new(query.engine).project(select_values % subquery_column).from(subquery)
+        else
+          query = collection.unscope(:order)
+          query.select_values = [select_values % column]
+          arel = query.arel
+        end
+
+        result = connection.select_one(arel, nil, query.bound_attributes)
 
         if result.blank?
           size = 0
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 53dbbd8c21..177b253645 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -857,9 +857,9 @@ module ActiveRecord
     # All Active Record models use this handler to determine the connection pool that they
     # should use.
     #
-    # The ConnectionHandler class is not coupled with the Active models, as it has no knowlodge
+    # The ConnectionHandler class is not coupled with the Active models, as it has no knowledge
     # about the model. The model needs to pass a specification name to the handler,
-    # in order to lookup the correct connection pool.
+    # in order to look up the correct connection pool.
     class ConnectionHandler
       def initialize
         # These caches are keyed by spec.name (ConnectionSpecification#name).
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
index 4682afc188..46d7f84efd 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -2,8 +2,33 @@ module ActiveRecord
   module ConnectionAdapters #:nodoc:
     # Abstract representation of an index definition on a table. Instances of
     # this type are typically created and returned by methods in database
-    # adapters. e.g. ActiveRecord::ConnectionAdapters::AbstractMysqlAdapter#indexes
-    IndexDefinition = Struct.new(:table, :name, :unique, :columns, :lengths, :orders, :where, :type, :using, :comment) #:nodoc:
+    # adapters. e.g. ActiveRecord::ConnectionAdapters::MySQL::SchemaStatements#indexes
+    class IndexDefinition # :nodoc:
+      attr_reader :table, :name, :unique, :columns, :lengths, :orders, :where, :type, :using, :comment
+
+      def initialize(
+        table, name,
+        unique = false,
+        columns = [],
+        lengths: {},
+        orders: {},
+        where: nil,
+        type: nil,
+        using: nil,
+        comment: nil
+      )
+        @table = table
+        @name = name
+        @unique = unique
+        @columns = columns
+        @lengths = lengths
+        @orders = orders
+        @where = where
+        @type = type
+        @using = using
+        @comment = comment
+      end
+    end
 
     # Abstract representation of a column definition. Instances of this type
     # are typically created by methods in TableDefinition, and added to the
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
index 6bb072dd73..19b7821494 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
@@ -149,57 +149,67 @@ module ActiveRecord
       end
 
       def begin_transaction(options = {})
-        run_commit_callbacks = !current_transaction.joinable?
-        transaction =
-          if @stack.empty?
-            RealTransaction.new(@connection, options, run_commit_callbacks: run_commit_callbacks)
-          else
-            SavepointTransaction.new(@connection, "active_record_#{@stack.size}", options,
-                                     run_commit_callbacks: run_commit_callbacks)
-          end
+        @connection.lock.synchronize do
+          run_commit_callbacks = !current_transaction.joinable?
+          transaction =
+            if @stack.empty?
+              RealTransaction.new(@connection, options, run_commit_callbacks: run_commit_callbacks)
+            else
+              SavepointTransaction.new(@connection, "active_record_#{@stack.size}", options,
+                                       run_commit_callbacks: run_commit_callbacks)
+            end
 
-        @stack.push(transaction)
-        transaction
+          @stack.push(transaction)
+          transaction
+        end
       end
 
       def commit_transaction
-        transaction = @stack.last
+        @connection.lock.synchronize do
+          transaction = @stack.last
 
-        begin
-          transaction.before_commit_records
-        ensure
-          @stack.pop
-        end
+          begin
+            transaction.before_commit_records
+          ensure
+            @stack.pop
+          end
 
-        transaction.commit
-        transaction.commit_records
+          transaction.commit
+          transaction.commit_records
+        end
       end
 
       def rollback_transaction(transaction = nil)
-        transaction ||= @stack.pop
-        transaction.rollback
-        transaction.rollback_records
+        @connection.lock.synchronize do
+          transaction ||= @stack.pop
+          transaction.rollback
+          transaction.rollback_records
+        end
       end
 
       def within_new_transaction(options = {})
-        transaction = begin_transaction options
-        yield
-      rescue Exception => error
-        if transaction
-          rollback_transaction
-          after_failure_actions(transaction, error)
-        end
-        raise
-      ensure
-        unless error
-          if Thread.current.status == "aborting"
-            rollback_transaction if transaction
-          else
-            begin
-              commit_transaction
-            rescue Exception
-              rollback_transaction(transaction) unless transaction.state.completed?
-              raise
+        @connection.lock.synchronize do
+          begin
+            transaction = begin_transaction options
+            yield
+          rescue Exception => error
+            if transaction
+              rollback_transaction
+              after_failure_actions(transaction, error)
+            end
+            raise
+          ensure
+            unless error
+              if Thread.current.status == "aborting"
+                rollback_transaction if transaction
+              else
+                begin
+                  commit_transaction
+                rescue Exception
+                  rollback_transaction(transaction) unless transaction.state.completed?
+                  raise
+                end
+              end
             end
           end
         end
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 96083e6519..85d6fbe8b3 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -74,7 +74,7 @@ module ActiveRecord
       SIMPLE_INT = /\A\d+\z/
 
       attr_accessor :visitor, :pool
-      attr_reader :schema_cache, :owner, :logger, :prepared_statements
+      attr_reader :schema_cache, :owner, :logger, :prepared_statements, :lock
       alias :in_use? :owner
 
       def self.type_cast_config_to_integer(config)
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 f118e086bb..c742799aab 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -48,9 +48,6 @@ module ActiveRecord
         json:        { name: "json" },
       }
 
-      INDEX_TYPES  = [:fulltext, :spatial]
-      INDEX_USINGS = [:btree, :hash]
-
       class StatementPool < ConnectionAdapters::StatementPool
         private def dealloc(stmt)
           stmt[:stmt].close
@@ -67,14 +64,6 @@ module ActiveRecord
         end
       end
 
-      CHARSETS_OF_4BYTES_MAXLEN = ["utf8mb4", "utf16", "utf16le", "utf32"]
-
-      def internal_string_options_for_primary_key # :nodoc:
-        super.tap { |options|
-          options[:collation] = collation.sub(/\A[^_]+/, "utf8") if CHARSETS_OF_4BYTES_MAXLEN.include?(charset)
-        }
-      end
-
       def version #:nodoc:
         @version ||= Version.new(full_version.match(/^\d+\.\d+\.\d+/)[0])
       end
@@ -93,10 +82,8 @@ module ActiveRecord
         true
       end
 
-      # Technically MySQL allows to create indexes with the sort order syntax
-      # but at the moment (5.5) it doesn't yet implement them
       def supports_index_sort_order?
-        true
+        !mariadb? && version >= "8.0.1"
       end
 
       def supports_transaction_isolation?
@@ -304,36 +291,6 @@ module ActiveRecord
         execute "TRUNCATE TABLE #{quote_table_name(table_name)}", name
       end
 
-      # Returns an array of indexes for the given table.
-      def indexes(table_name, name = nil) #:nodoc:
-        if name
-          ActiveSupport::Deprecation.warn(<<-MSG.squish)
-            Passing name to #indexes is deprecated without replacement.
-          MSG
-        end
-
-        indexes = []
-        current_index = nil
-        execute_and_free("SHOW KEYS FROM #{quote_table_name(table_name)}", "SCHEMA") do |result|
-          each_hash(result) do |row|
-            if current_index != row[:Key_name]
-              next if row[:Key_name] == "PRIMARY" # skip the primary key
-              current_index = row[:Key_name]
-
-              mysql_index_type = row[:Index_type].downcase.to_sym
-              index_type  = INDEX_TYPES.include?(mysql_index_type)  ? mysql_index_type : nil
-              index_using = INDEX_USINGS.include?(mysql_index_type) ? mysql_index_type : nil
-              indexes << IndexDefinition.new(row[:Table], row[:Key_name], row[:Non_unique].to_i == 0, [], {}, nil, nil, index_type, index_using, row[:Index_comment].presence)
-            end
-
-            indexes.last.columns << row[:Column_name]
-            indexes.last.lengths.merge!(row[:Column_name] => row[:Sub_part].to_i) if row[:Sub_part]
-          end
-        end
-
-        indexes
-      end
-
       def table_comment(table_name) # :nodoc:
         scope = quoted_scope(table_name)
 
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
index 3e0afd9761..e2ba0ba1a0 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
@@ -55,13 +55,14 @@ module ActiveRecord
           def extract_expression_for_virtual_column(column)
             if mariadb?
               create_table_info = create_table_info(column.table_name)
-              if %r/#{quote_column_name(column.name)} #{Regexp.quote(column.sql_type)} AS \((?<expression>.+?)\) #{column.extra}/m =~ create_table_info
+              if %r/#{quote_column_name(column.name)} #{Regexp.quote(column.sql_type)}(?: COLLATE \w+)? AS \((?<expression>.+?)\) #{column.extra}/ =~ create_table_info
                 $~[:expression].inspect
               end
             else
+              scope = quoted_scope(column.table_name)
               sql = "SELECT generation_expression FROM information_schema.columns" \
-                    " WHERE table_schema = #{quote(@config[:database])}" \
-                    "   AND table_name = #{quote(column.table_name)}" \
+                    " WHERE table_schema = #{scope[:schema]}" \
+                    "   AND table_name = #{scope[:name]}" \
                     "   AND column_name = #{quote(column.name)}"
               select_value(sql, "SCHEMA").inspect
             end
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
index 9e2d0fb5e7..f9e1e046ea 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
@@ -2,7 +2,60 @@ module ActiveRecord
   module ConnectionAdapters
     module MySQL
       module SchemaStatements # :nodoc:
+        # Returns an array of indexes for the given table.
+        def indexes(table_name, name = nil)
+          if name
+            ActiveSupport::Deprecation.warn(<<-MSG.squish)
+              Passing name to #indexes is deprecated without replacement.
+            MSG
+          end
+
+          indexes = []
+          current_index = nil
+          execute_and_free("SHOW KEYS FROM #{quote_table_name(table_name)}", "SCHEMA") do |result|
+            each_hash(result) do |row|
+              if current_index != row[:Key_name]
+                next if row[:Key_name] == "PRIMARY" # skip the primary key
+                current_index = row[:Key_name]
+
+                mysql_index_type = row[:Index_type].downcase.to_sym
+                case mysql_index_type
+                when :fulltext, :spatial
+                  index_type = mysql_index_type
+                when :btree, :hash
+                  index_using = mysql_index_type
+                end
+
+                indexes << IndexDefinition.new(
+                  row[:Table],
+                  row[:Key_name],
+                  row[:Non_unique].to_i == 0,
+                  type: index_type,
+                  using: index_using,
+                  comment: row[:Index_comment].presence
+                )
+              end
+
+              indexes.last.columns << row[:Column_name]
+              indexes.last.lengths.merge!(row[:Column_name] => row[:Sub_part].to_i) if row[:Sub_part]
+              indexes.last.orders.merge!(row[:Column_name] => :desc) if row[:Collation] == "D"
+            end
+          end
+
+          indexes
+        end
+
+        def internal_string_options_for_primary_key
+          super.tap do |options|
+            if CHARSETS_OF_4BYTES_MAXLEN.include?(charset) && (mariadb? || version < "8.0.0")
+              options[:collation] = collation.sub(/\A[^_]+/, "utf8")
+            end
+          end
+        end
+
         private
+          CHARSETS_OF_4BYTES_MAXLEN = ["utf8mb4", "utf16", "utf16le", "utf32"]
+
           def schema_creation
             MySQL::SchemaCreation.new(self)
           end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index 1d439acb07..5b483ad4ab 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -140,8 +140,17 @@ module ActiveRecord
               ]
             end
 
-            IndexDefinition.new(table_name, index_name, unique, columns, [], orders, where, nil, using.to_sym, comment.presence)
-          end.compact
+            IndexDefinition.new(
+              table_name,
+              index_name,
+              unique,
+              columns,
+              orders: orders,
+              where: where,
+              using: using.to_sym,
+              comment: comment.presence
+            )
+          end
         end
 
         def table_options(table_name) # :nodoc:
@@ -344,13 +353,17 @@ module ActiveRecord
 
         def primary_keys(table_name) # :nodoc:
           select_values(<<-SQL.strip_heredoc, "SCHEMA")
-            SELECT a.attname FROM pg_index i
-            CROSS JOIN generate_subscripts(i.indkey, 1) k
-             JOIN pg_attribute a
-               ON a.attrelid = i.indrelid
-              AND a.attnum = i.indkey[k]
-            WHERE i.indrelid = #{quote(quote_table_name(table_name))}::regclass
-              AND i.indisprimary
+            SELECT a.attname
+              FROM (
+                     SELECT indrelid, indkey, generate_subscripts(indkey, 1) idx
+                       FROM pg_index
+                      WHERE indrelid = #{quote(quote_table_name(table_name))}::regclass
+                        AND indisprimary
+                   ) i
+              JOIN pg_attribute a
+                ON a.attrelid = i.indrelid
+               AND a.attnum = i.indkey[i.idx]
+             ORDER BY i.idx
           SQL
         end
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 0ad114165e..7ae9bd9a5f 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -239,7 +239,9 @@ module ActiveRecord
 
       # Is this connection alive and ready for queries?
       def active?
-        @connection.query "SELECT 1"
+        @lock.synchronize do
+          @connection.query "SELECT 1"
+        end
         true
       rescue PG::Error
         false
@@ -247,26 +249,32 @@ module ActiveRecord
 
       # Close then reopen the connection.
       def reconnect!
-        super
-        @connection.reset
-        configure_connection
+        @lock.synchronize do
+          super
+          @connection.reset
+          configure_connection
+        end
       end
 
       def reset!
-        clear_cache!
-        reset_transaction
-        unless @connection.transaction_status == ::PG::PQTRANS_IDLE
-          @connection.query "ROLLBACK"
+        @lock.synchronize do
+          clear_cache!
+          reset_transaction
+          unless @connection.transaction_status == ::PG::PQTRANS_IDLE
+            @connection.query "ROLLBACK"
+          end
+          @connection.query "DISCARD ALL"
+          configure_connection
         end
-        @connection.query "DISCARD ALL"
-        configure_connection
       end
 
       # Disconnects from the database if already connected. Otherwise, this
       # method does nothing.
       def disconnect!
-        super
-        @connection.close rescue nil
+        @lock.synchronize do
+          super
+          @connection.close rescue nil
+        end
       end
 
       def native_database_types #:nodoc:
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
index 8066a05c5e..e02491edb6 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
@@ -2,6 +2,41 @@ module ActiveRecord
   module ConnectionAdapters
     module SQLite3
       module SchemaStatements # :nodoc:
+        # Returns an array of indexes for the given table.
+        def indexes(table_name, name = nil)
+          if name
+            ActiveSupport::Deprecation.warn(<<-MSG.squish)
+              Passing name to #indexes is deprecated without replacement.
+            MSG
+          end
+
+          exec_query("PRAGMA index_list(#{quote_table_name(table_name)})", "SCHEMA").map do |row|
+            index_sql = select_value(<<-SQL, "SCHEMA")
+              SELECT sql
+              FROM sqlite_master
+              WHERE name = #{quote(row['name'])} AND type = 'index'
+              UNION ALL
+              SELECT sql
+              FROM sqlite_temp_master
+              WHERE name = #{quote(row['name'])} AND type = 'index'
+            SQL
+
+            /\sWHERE\s+(?<where>.+)$/i =~ index_sql
+
+            columns = exec_query("PRAGMA index_info(#{quote(row['name'])})", "SCHEMA").map do |col|
+              col["name"]
+            end
+
+            IndexDefinition.new(
+              table_name,
+              row["name"],
+              row["unique"] != 0,
+              columns,
+              where: where
+            )
+          end
+        end
+
         private
           def schema_creation
             SQLite3::SchemaCreation.new(self)
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index c54b88f7d1..e2c05ccc4e 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -259,37 +259,6 @@ module ActiveRecord
 
       # SCHEMA STATEMENTS ========================================
 
-      # Returns an array of indexes for the given table.
-      def indexes(table_name, name = nil) #:nodoc:
-        if name
-          ActiveSupport::Deprecation.warn(<<-MSG.squish)
-            Passing name to #indexes is deprecated without replacement.
-          MSG
-        end
-
-        exec_query("PRAGMA index_list(#{quote_table_name(table_name)})", "SCHEMA").map do |row|
-          sql = <<-SQL
-            SELECT sql
-            FROM sqlite_master
-            WHERE name=#{quote(row['name'])} AND type='index'
-            UNION ALL
-            SELECT sql
-            FROM sqlite_temp_master
-            WHERE name=#{quote(row['name'])} AND type='index'
-          SQL
-          index_sql = exec_query(sql).first["sql"]
-          match = /\sWHERE\s+(.+)$/i.match(index_sql)
-          where = match[1] if match
-          IndexDefinition.new(
-            table_name,
-            row["name"],
-            row["unique"] != 0,
-            exec_query("PRAGMA index_info('#{row['name']}')", "SCHEMA").map { |col|
-              col["name"]
-            }, nil, nil, where)
-        end
-      end
-
       def primary_keys(table_name) # :nodoc:
         pks = table_structure(table_name).select { |f| f["pk"] > 0 }
         pks.sort_by { |f| f["pk"] }.map { |f| f["name"] }
diff --git a/activerecord/lib/active_record/dynamic_matchers.rb b/activerecord/lib/active_record/dynamic_matchers.rb
index 08d42f3dd4..d9912cfb22 100644
--- a/activerecord/lib/active_record/dynamic_matchers.rb
+++ b/activerecord/lib/active_record/dynamic_matchers.rb
@@ -1,4 +1,3 @@
-
 module ActiveRecord
   module DynamicMatchers #:nodoc:
     def respond_to_missing?(name, include_private = false)
diff --git a/activerecord/lib/active_record/fixtures.rb b/activerecord/lib/active_record/fixtures.rb
index e79167d568..c19216702c 100644
--- a/activerecord/lib/active_record/fixtures.rb
+++ b/activerecord/lib/active_record/fixtures.rb
@@ -70,13 +70,32 @@ module ActiveRecord
   # test. To ensure consistent data, the environment deletes the fixtures before running the load.
   #
   # In addition to being available in the database, the fixture's data may also be accessed by
-  # using a special dynamic method, which has the same name as the model, and accepts the
-  # name of the fixture to instantiate:
+  # using a special dynamic method, which has the same name as the model.
   #
-  #   test "find" do
+  # Passing in a fixture name to this dynamic method returns the fixture matching this name:
+  #
+  #   test "find one" do
   #     assert_equal "Ruby on Rails", web_sites(:rubyonrails).name
   #   end
   #
+  # Passing in multiple fixture names returns all fixtures matching these names:
+  #
+  #   test "find all by name" do
+  #     assert_equal 2, web_sites(:rubyonrails, :google).length
+  #   end
+  #
+  # Passing in no arguments returns all fixtures:
+  #
+  #   test "find all" do
+  #     assert_equal 2, web_sites.length
+  #   end
+  #
+  # Passing in any fixture name that does not exist will raise <tt>StandardError</tt>:
+  #
+  #   test "find by name that does not exist" do
+  #     assert_raise(StandardError) { web_sites(:reddit) }
+  #   end
+  #
   # Alternatively, you may enable auto-instantiation of the fixture data. For instance, take the
   # following tests:
   #
@@ -909,6 +928,8 @@ module ActiveRecord
 
             define_method(accessor_name) do |*fixture_names|
               force_reload = fixture_names.pop if fixture_names.last == true || fixture_names.last == :reload
+              return_single_record = fixture_names.size == 1
+              fixture_names = @loaded_fixtures[fs_name].fixtures.keys if fixture_names.empty?
 
               @fixture_cache[fs_name] ||= {}
 
@@ -923,7 +944,7 @@ module ActiveRecord
                 end
               end
 
-              instances.size == 1 ? instances.first : instances
+              return_single_record ? instances.first : instances
             end
             private accessor_name
           end
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index 4e1df1432c..51c82f4ced 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -1104,13 +1104,21 @@ module ActiveRecord
 
       def move(direction, migrations_paths, steps)
         migrator = new(direction, migrations(migrations_paths))
-        start_index = migrator.migrations.index(migrator.current_migration)
 
-        if start_index
-          finish = migrator.migrations[start_index + steps]
-          version = finish ? finish.version : 0
-          send(direction, migrations_paths, version)
+        if current_version != 0 && !migrator.current_migration
+          raise UnknownMigrationVersionError.new(current_version)
         end
+
+        start_index =
+          if current_version == 0
+            0
+          else
+            migrator.migrations.index(migrator.current_migration)
+          end
+
+        finish = migrator.migrations[start_index + steps]
+        version = finish ? finish.version : 0
+        send(direction, migrations_paths, version)
       end
     end
 
diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index 7ceb7d1a55..f652c7c3a1 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -100,6 +100,10 @@ module ActiveRecord
       !(@new_record || @destroyed)
     end
 
+    ##
+    # :call-seq:
+    #   save(*args)
+    #
     # Saves the model.
     #
     # If the model is new, a record gets created in the database, otherwise
@@ -121,12 +125,16 @@ module ActiveRecord
     #
     # Attributes marked as readonly are silently ignored if the record is
     # being updated.
-    def save(*args)
-      create_or_update(*args)
+    def save(*args, &block)
+      create_or_update(*args, &block)
     rescue ActiveRecord::RecordInvalid
       false
     end
 
+    ##
+    # :call-seq:
+    #   save!(*args)
+    #
     # Saves the model.
     #
     # If the model is new, a record gets created in the database, otherwise
@@ -150,8 +158,8 @@ module ActiveRecord
     # being updated.
     #
     # Unless an error is raised, returns true.
-    def save!(*args)
-      create_or_update(*args) || raise(RecordNotSaved.new("Failed to save the record", self))
+    def save!(*args, &block)
+      create_or_update(*args, &block) || raise(RecordNotSaved.new("Failed to save the record", self))
     end
 
     # Deletes the record in the database and freezes this instance to
@@ -550,9 +558,9 @@ module ActiveRecord
       self.class.unscoped.where(self.class.primary_key => id)
     end
 
-    def create_or_update(*args)
+    def create_or_update(*args, &block)
       _raise_readonly_record_error if readonly?
-      result = new_record? ? _create_record : _update_record(*args)
+      result = new_record? ? _create_record(&block) : _update_record(*args, &block)
       result != false
     end
 
@@ -567,6 +575,9 @@ module ActiveRecord
         rows_affected = self.class.unscoped._update_record attributes_values, id, id_in_database
         @_trigger_update_callback = rows_affected > 0
       end
+
+      yield(self) if block_given?
+
       rows_affected
     end
 
@@ -579,6 +590,9 @@ module ActiveRecord
       self.id ||= new_id if self.class.primary_key
 
       @new_record = false
+
+      yield(self) if block_given?
+
       id
     end
 
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index 5d24f5f5ca..a1459c87c6 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -312,16 +312,7 @@ module ActiveRecord
       relation = apply_join_dependency(self, construct_join_dependency(eager_loading: false))
       return false if ActiveRecord::NullRelation === relation
 
-      relation = relation.except(:select, :distinct).select(ONE_AS_ONE).limit(1)
-
-      case conditions
-      when Array, Hash
-        relation = relation.where(conditions)
-      else
-        unless conditions == :none
-          relation = relation.where(primary_key => conditions)
-        end
-      end
+      relation = construct_relation_for_exists(relation, conditions)
 
       connection.select_value(relation, "#{name} Exists", relation.bound_attributes) ? true : false
     rescue ::RangeError
@@ -391,6 +382,19 @@ module ActiveRecord
         end
       end
 
+      def construct_relation_for_exists(relation, conditions)
+        relation = relation.except(:select, :distinct, :order)._select!(ONE_AS_ONE).limit!(1)
+
+        case conditions
+        when Array, Hash
+          relation.where!(conditions)
+        else
+          relation.where!(primary_key => conditions) unless conditions == :none
+        end
+
+        relation
+      end
+
       def construct_join_dependency(joins = [], eager_loading: true)
         including = eager_load_values + includes_values
         ActiveRecord::Associations::JoinDependency.new(@klass, including, joins, eager_loading: eager_loading)
@@ -401,8 +405,7 @@ module ActiveRecord
       end
 
       def apply_join_dependency(relation, join_dependency)
-        relation = relation.except(:includes, :eager_load, :preload)
-        relation = relation.joins join_dependency
+        relation = relation.except(:includes, :eager_load, :preload).joins!(join_dependency)
 
         if using_limitable_reflections?(join_dependency.reflections)
           relation
diff --git a/activerecord/lib/active_record/relation/predicate_builder.rb b/activerecord/lib/active_record/relation/predicate_builder.rb
index fca914aedd..183fe91c05 100644
--- a/activerecord/lib/active_record/relation/predicate_builder.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder.rb
@@ -1,13 +1,14 @@
+require "active_record/relation/predicate_builder/array_handler"
+require "active_record/relation/predicate_builder/base_handler"
+require "active_record/relation/predicate_builder/basic_object_handler"
+require "active_record/relation/predicate_builder/range_handler"
+require "active_record/relation/predicate_builder/relation_handler"
+
+require "active_record/relation/predicate_builder/association_query_value"
+require "active_record/relation/predicate_builder/polymorphic_array_value"
+
 module ActiveRecord
   class PredicateBuilder # :nodoc:
-    require "active_record/relation/predicate_builder/array_handler"
-    require "active_record/relation/predicate_builder/association_query_handler"
-    require "active_record/relation/predicate_builder/base_handler"
-    require "active_record/relation/predicate_builder/basic_object_handler"
-    require "active_record/relation/predicate_builder/polymorphic_array_handler"
-    require "active_record/relation/predicate_builder/range_handler"
-    require "active_record/relation/predicate_builder/relation_handler"
-
     delegate :resolve_column_aliases, to: :table
 
     def initialize(table)
@@ -20,8 +21,6 @@ module ActiveRecord
       register_handler(RangeHandler::RangeWithBinds, RangeHandler.new)
       register_handler(Relation, RelationHandler.new)
       register_handler(Array, ArrayHandler.new(self))
-      register_handler(AssociationQueryValue, AssociationQueryHandler.new(self))
-      register_handler(PolymorphicArrayValue, PolymorphicArrayHandler.new(self))
     end
 
     def build_from_hash(attributes)
@@ -87,7 +86,6 @@ module ActiveRecord
         binds = []
 
         attributes.each do |column_name, value|
-          binds.concat(value.bound_attributes) if value.is_a?(Relation)
           case
           when value.is_a?(Hash) && !table.has_column?(column_name)
             attrs, bvs = associated_predicate_builder(column_name).create_binds_for_hash(value)
@@ -99,7 +97,21 @@ module ActiveRecord
             #
             # For polymorphic relationships, find the foreign key and type:
             # PriceEstimate.where(estimate_of: treasure)
-            result[column_name] = AssociationQueryHandler.value_for(table, column_name, value)
+            associated_table = table.associated_table(column_name)
+            if associated_table.polymorphic_association?
+              case value.is_a?(Array) ? value.first : value
+              when Base, Relation
+                value = [value] unless value.is_a?(Array)
+                klass = PolymorphicArrayValue
+              end
+            end
+
+            klass ||= AssociationQueryValue
+            result[column_name] = klass.new(associated_table, value).queries.map do |query|
+              attrs, bvs = create_binds_for_hash(query)
+              binds.concat(bvs)
+              attrs
+            end
           when value.is_a?(Range) && !table.type(column_name).respond_to?(:subtype)
             first = value.begin
             last = value.end
@@ -117,6 +129,8 @@ module ActiveRecord
             if can_be_bound?(column_name, value)
               result[column_name] = Arel::Nodes::BindParam.new
               binds << build_bind_param(column_name, value)
+            elsif value.is_a?(Relation)
+              binds.concat(value.bound_attributes)
             end
           end
         end
diff --git a/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
index 88b6c37d43..1068e700e2 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
@@ -6,11 +6,11 @@ module ActiveRecord
       end
 
       def call(attribute, value)
+        return attribute.in([]) if value.empty?
+        return queries_predicates(value) if value.all? { |v| v.is_a?(Hash) }
+
         values = value.map { |x| x.is_a?(Base) ? x.id : x }
         nils, values = values.partition(&:nil?)
-
-        return attribute.in([]) if values.empty? && nils.empty?
-
         ranges, values = values.partition { |v| v.is_a?(Range) }
 
         values_predicate =
@@ -26,7 +26,7 @@ module ActiveRecord
 
         array_predicates = ranges.map { |range| predicate_builder.build(attribute, range) }
         array_predicates.unshift(values_predicate)
-        array_predicates.inject { |composite, predicate| composite.or(predicate) }
+        array_predicates.inject(&:or)
       end
 
       # TODO Change this to private once we've dropped Ruby 2.2 support.
@@ -40,6 +40,17 @@ module ActiveRecord
             other
           end
         end
+
+      private
+        def queries_predicates(queries)
+          if queries.size > 1
+            queries.map do |query|
+              Arel::Nodes::And.new(predicate_builder.build_from_hash(query))
+            end.inject(&:or)
+          else
+            predicate_builder.build_from_hash(queries.first)
+          end
+        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/relation/predicate_builder/association_query_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/association_query_handler.rb
deleted file mode 100644
index 29860ec677..0000000000
--- a/activerecord/lib/active_record/relation/predicate_builder/association_query_handler.rb
+++ /dev/null
@@ -1,88 +0,0 @@
-module ActiveRecord
-  class PredicateBuilder
-    class AssociationQueryHandler # :nodoc:
-      def self.value_for(table, column, value)
-        associated_table = table.associated_table(column)
-        klass = if associated_table.polymorphic_association? && ::Array === value && value.first.is_a?(Base)
-          PolymorphicArrayValue
-        else
-          AssociationQueryValue
-        end
-
-        klass.new(associated_table, value)
-      end
-
-      def initialize(predicate_builder)
-        @predicate_builder = predicate_builder
-      end
-
-      def call(attribute, value)
-        queries = {}
-
-        table = value.associated_table
-        if value.base_class
-          queries[table.association_foreign_type.to_s] = value.base_class.name
-        end
-
-        queries[table.association_foreign_key.to_s] = value.ids
-        predicate_builder.build_from_hash(queries)
-      end
-
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :predicate_builder
-    end
-
-    class AssociationQueryValue # :nodoc:
-      attr_reader :associated_table, :value
-
-      def initialize(associated_table, value)
-        @associated_table = associated_table
-        @value = value
-      end
-
-      def ids
-        case value
-        when Relation
-          value.select(primary_key)
-        when Array
-          value.map { |v| convert_to_id(v) }
-        else
-          convert_to_id(value)
-        end
-      end
-
-      def base_class
-        if associated_table.polymorphic_association?
-          @base_class ||= polymorphic_base_class_from_value
-        end
-      end
-
-      private
-
-        def primary_key
-          associated_table.association_primary_key(base_class)
-        end
-
-        def polymorphic_base_class_from_value
-          case value
-          when Relation
-            value.klass.base_class
-          when Base
-            value.class.base_class
-          end
-        end
-
-        def convert_to_id(value)
-          case value
-          when Base
-            value._read_attribute(primary_key)
-          else
-            value
-          end
-        end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/relation/predicate_builder/association_query_value.rb b/activerecord/lib/active_record/relation/predicate_builder/association_query_value.rb
new file mode 100644
index 0000000000..2fe0f81cab
--- /dev/null
+++ b/activerecord/lib/active_record/relation/predicate_builder/association_query_value.rb
@@ -0,0 +1,41 @@
+module ActiveRecord
+  class PredicateBuilder
+    class AssociationQueryValue # :nodoc:
+      attr_reader :associated_table, :value
+
+      def initialize(associated_table, value)
+        @associated_table = associated_table
+        @value = value
+      end
+
+      def queries
+        [associated_table.association_foreign_key.to_s => ids]
+      end
+
+      private
+        def ids
+          case value
+          when Relation
+            value.select_values.empty? ? value.select(primary_key) : value
+          when Array
+            value.map { |v| convert_to_id(v) }
+          else
+            convert_to_id(value)
+          end
+        end
+
+        def primary_key
+          associated_table.association_primary_key
+        end
+
+        def convert_to_id(value)
+          case value
+          when Base
+            value._read_attribute(primary_key)
+          else
+            value
+          end
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_handler.rb
deleted file mode 100644
index 335124c952..0000000000
--- a/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_handler.rb
+++ /dev/null
@@ -1,59 +0,0 @@
-module ActiveRecord
-  class PredicateBuilder
-    class PolymorphicArrayHandler # :nodoc:
-      def initialize(predicate_builder)
-        @predicate_builder = predicate_builder
-      end
-
-      def call(attribute, value)
-        table = value.associated_table
-        queries = value.type_to_ids_mapping.map do |type, ids|
-          { table.association_foreign_type.to_s => type, table.association_foreign_key.to_s => ids }
-        end
-
-        predicates = queries.map { |query| predicate_builder.build_from_hash(query) }
-
-        if predicates.size > 1
-          type_and_ids_predicates = predicates.map { |type_predicate, id_predicate| Arel::Nodes::Grouping.new(type_predicate.and(id_predicate)) }
-          type_and_ids_predicates.inject(&:or)
-        else
-          predicates.first
-        end
-      end
-
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :predicate_builder
-    end
-
-    class PolymorphicArrayValue # :nodoc:
-      attr_reader :associated_table, :values
-
-      def initialize(associated_table, values)
-        @associated_table = associated_table
-        @values = values
-      end
-
-      def type_to_ids_mapping
-        default_hash = Hash.new { |hsh, key| hsh[key] = [] }
-        values.each_with_object(default_hash) { |value, hash| hash[base_class(value).name] << convert_to_id(value) }
-      end
-
-      private
-
-        def primary_key(value)
-          associated_table.association_primary_key(base_class(value))
-        end
-
-        def base_class(value)
-          value.class.base_class
-        end
-
-        def convert_to_id(value)
-          value._read_attribute(primary_key(value))
-        end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_value.rb b/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_value.rb
new file mode 100644
index 0000000000..9bb2f8c8dc
--- /dev/null
+++ b/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_value.rb
@@ -0,0 +1,49 @@
+module ActiveRecord
+  class PredicateBuilder
+    class PolymorphicArrayValue # :nodoc:
+      attr_reader :associated_table, :values
+
+      def initialize(associated_table, values)
+        @associated_table = associated_table
+        @values = values
+      end
+
+      def queries
+        type_to_ids_mapping.map do |type, ids|
+          {
+            associated_table.association_foreign_type.to_s => type,
+            associated_table.association_foreign_key.to_s => ids.size > 1 ? ids : ids.first
+          }
+        end
+      end
+
+      private
+        def type_to_ids_mapping
+          default_hash = Hash.new { |hsh, key| hsh[key] = [] }
+          values.each_with_object(default_hash) { |value, hash| hash[base_class(value).name] << convert_to_id(value) }
+        end
+
+        def primary_key(value)
+          associated_table.association_primary_key(base_class(value))
+        end
+
+        def base_class(value)
+          case value
+          when Base
+            value.class.base_class
+          when Relation
+            value.klass.base_class
+          end
+        end
+
+        def convert_to_id(value)
+          case value
+          when Base
+            value._read_attribute(primary_key(value))
+          when Relation
+            value.select(primary_key(value))
+          end
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/schema_dumper.rb b/activerecord/lib/active_record/schema_dumper.rb
index 2bbfd01698..94d63765c9 100644
--- a/activerecord/lib/active_record/schema_dumper.rb
+++ b/activerecord/lib/active_record/schema_dumper.rb
@@ -47,9 +47,18 @@ module ActiveRecord
         @options = options
       end
 
-      def header(stream)
-        define_params = @version ? "version: #{@version}" : ""
+      # turns 20170404131909 into "2017_04_04_131909"
+      def formatted_version
+        stringified = @version.to_s
+        return stringified unless stringified.length == 14
+        stringified.insert(4, "_").insert(7, "_").insert(10, "_")
+      end
 
+      def define_params
+        @version ? "version: #{formatted_version}" : ""
+      end
+
+      def header(stream)
         stream.puts <<HEADER
 # This file is auto-generated from the current state of the database. Instead
 # of editing this file, please use the migrations feature of Active Record to
diff --git a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
index 920830b9cf..c05f0a8fbb 100644
--- a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
@@ -104,7 +104,7 @@ module ActiveRecord
 
         def grant_statement
           <<-SQL
-GRANT ALL PRIVILEGES ON #{configuration['database']}.*
+GRANT ALL PRIVILEGES ON `#{configuration['database']}`.*
   TO '#{configuration['username']}'@'localhost'
 IDENTIFIED BY '#{configuration['password']}' WITH GRANT OPTION;
           SQL