[Rails5] Update ar5_batching initializer

config/initializers/ar5_batching.rb

-# Port ActiveRecord::Relation#in_batches from ActiveRecord 5.
-# https://github.com/rails/rails/blob/ac027338e4a165273607dccee49a3d38bc836794/activerecord/lib/active_record/relation/batches.rb#L184
-# TODO: this can be removed once we're using AR5.
-raise "Vendored ActiveRecord 5 code! Delete #{__FILE__}!" if ActiveRecord::VERSION::MAJOR >= 5
-
-module ActiveRecord
-  module Batches
-    # Differences from upstream: enumerator support was removed, and custom
-    # order/limit clauses are ignored without a warning.
-    def in_batches(of: 1000, start: nil, finish: nil, load: false)
-      raise "Must provide a block" unless block_given?
-
-      relation = self.reorder(batch_order).limit(of)
-      relation = relation.where(arel_table[primary_key].gteq(start)) if start
-      relation = relation.where(arel_table[primary_key].lteq(finish)) if finish
-      batch_relation = relation
-
-      loop do
-        if load
-          records = batch_relation.records
-          ids = records.map(&:id)
-          yielded_relation = self.where(primary_key => ids)
-          yielded_relation.load_records(records)
-        else
-          ids = batch_relation.pluck(primary_key)
-          yielded_relation = self.where(primary_key => ids)
+# Remove this file when upgraded to rails 5.0.
+unless Gitlab.rails5?
+  module ActiveRecord
+    module Batches
+      # Differences from upstream: enumerator support was removed, and custom
+      # order/limit clauses are ignored without a warning.
+      def in_batches(of: 1000, start: nil, finish: nil, load: false)
+        raise "Must provide a block" unless block_given?
+
+        relation = self.reorder(batch_order).limit(of)
+        relation = relation.where(arel_table[primary_key].gteq(start)) if start
+        relation = relation.where(arel_table[primary_key].lteq(finish)) if finish
+        batch_relation = relation
+
+        loop do
+          if load
+            records = batch_relation.records
+            ids = records.map(&:id)
+            yielded_relation = self.where(primary_key => ids)
+            yielded_relation.load_records(records)
+          else
+            ids = batch_relation.pluck(primary_key)
+            yielded_relation = self.where(primary_key => ids)
+          end
+
+          break if ids.empty?
+
+          primary_key_offset = ids.last
+          raise ArgumentError.new("Primary key not included in the custom select clause") unless primary_key_offset
+
+          yield yielded_relation
+
+          break if ids.length < of
+
+          batch_relation = relation.where(arel_table[primary_key].gt(primary_key_offset))
         end
-
-        break if ids.empty?
-
-        primary_key_offset = ids.last
-        raise ArgumentError.new("Primary key not included in the custom select clause") unless primary_key_offset
-
-        yield yielded_relation
-
-        break if ids.length < of
-
-        batch_relation = relation.where(arel_table[primary_key].gt(primary_key_offset))
       end
     end
   end