Merge branch 'master' into set_binds

* master: (2794 commits)
  doc, API example on how to use `Model#exists?` with multiple IDs. [ci skip]
  Restore DATABASE_URL even if it's nil in connection_handler test
  [ci skip] - error_messages_for has been deprecated since 2.3.8 - lets reduce any confusion for users
  Ensure Active Record connection consistency
  Revert "ask the fixture set for the sql statements"
  Check `respond_to` before delegation due to: https://github.com/ruby/ruby/commit/d781caaf313b8649948c107bba277e5ad7307314
  Adding Hash#compact and Hash#compact! methods
  MySQL version 4.1 was EOL on December 31, 2009 We should at least recommend modern versions of MySQL to users.
  clear cache on body close so that cache remains during rendering
  add a more restricted codepath for templates fixes #13390
  refactor generator tests to use block form of Tempfile
  Fix typo [ci skip]
  Move finish_template as the last public method in the generator
  Minor typos fix [ci skip]
  make `change_column_null` reversible. Closes #13576.
  create/drop test and development databases only if RAILS_ENV is nil
  Revert "Speedup String#to"
  typo fix in test name. [ci skip].
  `core_ext/string/access.rb` test what we are documenting.
  Fix typo in image_tag documentation
  ...

Conflicts:
	activerecord/lib/active_record/associations/join_dependency/join_association.rb
	activerecord/lib/active_record/relation/query_methods.rb

1 files changed, 54 insertions, 23 deletions

diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
index b921f2eddb..49b01909c6 100644
--- a/activerecord/lib/active_record/relation/batches.rb
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -11,7 +11,7 @@ module ActiveRecord
     # The #find_each method uses #find_in_batches with a batch size of 1000 (or as
     # specified by the +:batch_size+ option).
     #
-    #   Person.all.find_each do |person|
+    #   Person.find_each do |person|
     #     person.do_awesome_stuff
     #   end
     #
@@ -19,47 +19,78 @@ module ActiveRecord
     #     person.party_all_night!
     #   end
     #
-    #  You can also pass the +:start+ option to specify
-    #  an offset to control the starting point.
-    def find_each(options = {})
-      find_in_batches(options) do |records|
-        records.each { |record| yield record }
-      end
-    end
-
-    # Yields each batch of records that was found by the find +options+ as
-    # an array. The size of each batch is set by the +:batch_size+
-    # option; the default is 1000.
+    # If you do not provide a block to #find_each, it will return an Enumerator
+    # for chaining with other methods:
+    #
+    #   Person.find_each.with_index do |person, index|
+    #     person.award_trophy(index + 1)
+    #   end
+    #
+    # ==== Options
+    # * <tt>:batch_size</tt> - Specifies the size of the batch. Default to 1000.
+    # * <tt>:start</tt> - Specifies the starting point for the batch processing.
+    # This is especially useful if you want multiple workers dealing with
+    # the same processing queue. You can make worker 1 handle all the records
+    # between id 0 and 10,000 and worker 2 handle from 10,000 and beyond
+    # (by setting the +:start+ option on that worker).
     #
-    # You can control the starting point for the batch processing by
-    # supplying the +:start+ option. This is especially useful if you
-    # want multiple workers dealing with the same processing queue. You can
-    # make worker 1 handle all the records between id 0 and 10,000 and
-    # worker 2 handle from 10,000 and beyond (by setting the +:start+
-    # option on that worker).
+    #   # Let's process for a batch of 2000 records, skipping the first 2000 rows
+    #   Person.find_each(start: 2000, batch_size: 2000) do |person|
+    #     person.party_all_night!
+    #   end
     #
-    # It's not possible to set the order. That is automatically set to
+    # NOTE: It's not possible to set the order. That is automatically set to
     # ascending on the primary key ("id ASC") to make the batch ordering
     # work. This also means that this method only works with integer-based
-    # primary keys. You can't set the limit either, that's used to control
+    # primary keys.
+    #
+    # NOTE: You can't set the limit either, that's used to control
     # the batch sizes.
+    def find_each(options = {})
+      if block_given?
+        find_in_batches(options) do |records|
+          records.each { |record| yield record }
+        end
+      else
+        enum_for :find_each, options
+      end
+    end
+
+    # Yields each batch of records that was found by the find +options+ as
+    # an array.
     #
     #   Person.where("age > 21").find_in_batches do |group|
     #     sleep(50) # Make sure it doesn't get too crowded in there!
     #     group.each { |person| person.party_all_night! }
     #   end
     #
+    # ==== Options
+    # * <tt>:batch_size</tt> - Specifies the size of the batch. Default to 1000.
+    # * <tt>:start</tt> - Specifies the starting point for the batch processing.
+    # This is especially useful if you want multiple workers dealing with
+    # the same processing queue. You can make worker 1 handle all the records
+    # between id 0 and 10,000 and worker 2 handle from 10,000 and beyond
+    # (by setting the +:start+ option on that worker).
+    #
     #   # Let's process the next 2000 records
-    #   Person.all.find_in_batches(start: 2000, batch_size: 2000) do |group|
+    #   Person.find_in_batches(start: 2000, batch_size: 2000) do |group|
     #     group.each { |person| person.party_all_night! }
     #   end
+    #
+    # NOTE: It's not possible to set the order. That is automatically set to
+    # ascending on the primary key ("id ASC") to make the batch ordering
+    # work. This also means that this method only works with integer-based
+    # primary keys.
+    #
+    # NOTE: You can't set the limit either, that's used to control
+    # the batch sizes.
     def find_in_batches(options = {})
       options.assert_valid_keys(:start, :batch_size)
 
       relation = self
 
-      unless arel.orders.blank? && arel.taken.blank?
-        ActiveRecord::Base.logger.warn("Scoped order and limit are ignored, it's forced to be batch order and batch size")
+      if logger && (arel.orders.present? || arel.taken.present?)
+        logger.warn("Scoped order and limit are ignored, it's forced to be batch order and batch size")
       end
 
       start = options.delete(:start)