1 files changed, 25 insertions, 22 deletions

diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
index 2fd89882ff..4d14506965 100644
--- a/activerecord/lib/active_record/relation/batches.rb
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -1,21 +1,26 @@
-require 'active_support/core_ext/object/blank'
 
 module ActiveRecord
   module Batches
-    # Yields each record that was found by the find +options+. The find is
-    # performed by find_in_batches with a batch size of 1000 (or as
-    # specified by the <tt>:batch_size</tt> option).
+    # Looping through a collection of records from the database
+    # (using the +all+ method, for example) is very inefficient
+    # since it will try to instantiate all the objects at once.
     #
-    # Example:
+    # In that case, batch processing methods allow you to work
+    # with the records in batches, thereby greatly reducing memory consumption.
+    #
+    # 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.do_awesome_stuff
+    #   end
     #
     #   Person.where("age > 21").find_each do |person|
     #     person.party_all_night!
     #   end
     #
-    # Note: This method is only intended to use for batch processing of
-    # large amounts of records that wouldn't fit in memory all at once. If
-    # you just need to loop over less than 1000 records, it's probably
-    # better just to use the regular find methods.
+    #  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 }
@@ -23,14 +28,14 @@ module ActiveRecord
     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 <tt>:batch_size</tt>
+    # an array. The size of each batch is set by the +:batch_size+
     # option; the default is 1000.
     #
     # You can control the starting point for the batch processing by
-    # supplying the <tt>:start</tt> option. This is especially useful if you
+    # 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 <tt>:start</tt>
+    # worker 2 handle from 10,000 and beyond (by setting the +:start+
     # option on that worker).
     #
     # It's not possible to set the order. That is automatically set to
@@ -39,31 +44,29 @@ module ActiveRecord
     # primary keys. You can't set the limit either, that's used to control
     # the batch sizes.
     #
-    # Example:
-    #
     #   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
+    #
+    #   # Let's process the next 2000 records
+    #   Person.all.find_in_batches(start: 2000, batch_size: 2000) do |group|
+    #     group.each { |person| person.party_all_night! }
+    #   end
     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")
       end
 
-      if (finder_options = options.except(:start, :batch_size)).present?
-        raise "You can't specify an order, it's forced to be #{batch_order}" if options[:order].present?
-        raise "You can't specify a limit, it's forced to be the batch_size"  if options[:limit].present?
-
-        relation = apply_finder_options(finder_options)
-      end
-
       start = options.delete(:start).to_i
       batch_size = options.delete(:batch_size) || 1000
 
       relation = relation.reorder(batch_order).limit(batch_size)
-      records = relation.where(table[primary_key].gteq(start)).all
+      records = relation.where(table[primary_key].gteq(start)).to_a
 
       while records.any?
         records_size = records.size