1 files changed, 22 insertions, 16 deletions
diff --git a/activerecord/lib/active_record/relation/spawn_methods.rb b/activerecord/lib/active_record/relation/spawn_methods.rb
index 648a02f1cc..db5f1af5ca 100644
--- a/activerecord/lib/active_record/relation/spawn_methods.rb
+++ b/activerecord/lib/active_record/relation/spawn_methods.rb
@@ -3,10 +3,11 @@ require 'active_support/core_ext/object/blank'
 module ActiveRecord
   module SpawnMethods
     def merge(r)
-      merged_relation = clone
-      return merged_relation unless r
+      return self unless r
       return to_a & r if r.is_a?(Array)
 
+      merged_relation = clone
+
       Relation::ASSOCIATION_METHODS.each do |method|
         value = r.send(:"#{method}_values")
 
@@ -24,31 +25,36 @@ module ActiveRecord
         merged_relation.send(:"#{method}_values=", merged_relation.send(:"#{method}_values") + value) if value.present?
       end
 
-      merged_relation = merged_relation.joins(r.joins_values)
+      merged_relation.joins_values += r.joins_values
 
       merged_wheres = @where_values + r.where_values
 
-      # Remove duplicates, last one wins.
-      seen = {}
-      merged_wheres = merged_wheres.reverse.reject { |w|
-        nuke = false
-        if w.respond_to?(:operator) && w.operator == :==
-          name       = w.left.name
-          nuke       = seen[name]
-          seen[name] = true
-        end
-        nuke
-      }.reverse
+      unless @where_values.empty?
+        # Remove duplicates, last one wins.
+        seen = Hash.new { |h,table| h[table] = {} }
+        merged_wheres = merged_wheres.reverse.reject { |w|
+          nuke = false
+          if w.respond_to?(:operator) && w.operator == :==
+            name              = w.left.name
+            table             = w.left.relation.name
+            nuke              = seen[table][name]
+            seen[table][name] = true
+          end
+          nuke
+        }.reverse
+      end
 
       merged_relation.where_values = merged_wheres
 
-      (Relation::SINGLE_VALUE_METHODS - [:lock]).each do |method|
+      (Relation::SINGLE_VALUE_METHODS - [:lock, :create_with]).each do |method|
         value = r.send(:"#{method}_value")
         merged_relation.send(:"#{method}_value=", value) unless value.nil?
       end
 
       merged_relation.lock_value = r.lock_value unless merged_relation.lock_value
 
+      merged_relation = merged_relation.create_with(r.create_with_value) if r.create_with_value
+
       # Apply scope extension modules
       merged_relation.send :apply_modules, r.extensions
 
@@ -94,7 +100,7 @@ module ActiveRecord
 
       options.assert_valid_keys(VALID_FIND_OPTIONS)
       finders = options.dup
-      finders.delete_if { |key, value| value.nil? }
+      finders.delete_if { |key, value| value.nil? && key != :limit }
 
       ([:joins, :select, :group, :order, :having, :limit, :offset, :from, :lock, :readonly] & finders.keys).each do |finder|
         relation = relation.send(finder, finders[finder])