Added EachBatch for iterating tables in batches

This module provides a class method called `each_batch` that can be used
to iterate tables in batches in a more efficient way compared to Rails'
`in_batches` method. This commit also includes a RuboCop cop to
blacklist the use of `in_batches` in favour of this new method.

2 files changed, 17 insertions, 0 deletions

diff --git a/rubocop/cop/in_batches.rb b/rubocop/cop/in_batches.rb
new file mode 100644
index 00000000000..c0240187e66
--- /dev/null
+++ b/rubocop/cop/in_batches.rb
@@ -0,0 +1,16 @@
+require_relative '../model_helpers'
+
+module RuboCop
+  module Cop
+    # Cop that prevents the use of `in_batches`
+    class InBatches < RuboCop::Cop::Cop
+      MSG = 'Do not use `in_batches`, use `each_batch` from the EachBatch module instead'.freeze
+
+      def on_send(node)
+        return unless node.children[1] == :in_batches
+
+        add_offense(node, :selector)
+      end
+    end
+  end
+end
diff --git a/rubocop/rubocop.rb b/rubocop/rubocop.rb
index 1e70314598a..f76144275c9 100644
--- a/rubocop/rubocop.rb
+++ b/rubocop/rubocop.rb
@@ -5,6 +5,7 @@ require_relative 'cop/redirect_with_status'
 require_relative 'cop/polymorphic_associations'
 require_relative 'cop/project_path_helper'
 require_relative 'cop/active_record_dependent'
+require_relative 'cop/in_batches'
 require_relative 'cop/migration/add_column'
 require_relative 'cop/migration/add_column_with_default_to_large_table'
 require_relative 'cop/migration/add_concurrent_foreign_key'