add the query to AR::Relation#explain output

Rationale: this is more readable if serveral queries
are involved in one call. Also, it will be possible
to let AR log EXPLAINs automatically in production
mode, where queries are not even around.

1 files changed, 3 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index f0891440a6..0c32ad5139 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 require 'active_support/core_ext/object/blank'
 require 'active_support/core_ext/module/delegation'
 
@@ -155,8 +156,8 @@ module ActiveRecord
       end
 
       queries.map do |sql|
-        @klass.connection.explain(sql)
-      end.join
+        "EXPLAIN for: #{sql}\n#{@klass.connection.explain(sql)}"
+      end.join("\n")
     end
 
     def to_a