When .find_each is called without a block, return an Enumerator.

This lets us do things like call: .find_each.with_index

3 files changed, 36 insertions, 2 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 21b0a52180..ddd6377dc9 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,8 @@
+*   `find_each` now returns an `Enumerator` when called without a block, so that it
+    can be chained with other `Enumerable` methods.
+
+    *Ben Woosley*
+
 *   Fixture setup does no longer depend on `ActiveRecord::Base.configurations`.
     This is relevant when `ENV["DATABASE_URL"]` is used in place of a `database.yml`.
 
diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
index 41291844fc..91ea1756c4 100644
--- a/activerecord/lib/active_record/relation/batches.rb
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -19,6 +19,13 @@ module ActiveRecord
     #     person.party_all_night!
     #   end
     #
+    # 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.
@@ -40,8 +47,12 @@ module ActiveRecord
     # NOTE: You can't set the limit either, that's used to control
     # the batch sizes.
     def find_each(options = {})
-      find_in_batches(options) do |records|
-        records.each { |record| yield record }
+      if block_given?
+        find_in_batches(options) do |records|
+          records.each { |record| yield record }
+        end
+      else
+        enum_for :find_each, options
       end
     end
 
diff --git a/activerecord/test/cases/batches_test.rb b/activerecord/test/cases/batches_test.rb
index e09fa95756..1d6676da1c 100644
--- a/activerecord/test/cases/batches_test.rb
+++ b/activerecord/test/cases/batches_test.rb
@@ -26,6 +26,24 @@ class EachTest < ActiveRecord::TestCase
     end
   end
 
+  def test_each_should_return_an_enumerator_if_no_block_is_present
+    assert_queries(1) do
+      Post.find_each(:batch_size => 100000).with_index do |post, index|
+        assert_kind_of Post, post
+        assert_kind_of Integer, index
+      end
+    end
+  end
+
+  def test_each_enumerator_should_execute_one_query_per_batch
+    assert_queries(@total + 1) do
+      Post.find_each(:batch_size => 1).with_index do |post, index|
+        assert_kind_of Post, post
+        assert_kind_of Integer, index
+      end
+    end
+  end
+
   def test_each_should_raise_if_select_is_set_without_id
     assert_raise(RuntimeError) do
       Post.select(:title).find_each(:batch_size => 1) { |post| post }