From 30a576fa145a8a7d7f68ac295addb24465baf39a Mon Sep 17 00:00:00 2001
From: Damien Mathieu <42@dmathieu.com>
Date: Thu, 5 Jul 2012 13:24:59 +0200
Subject: [PATCH] fix querying with an empty hash

Closes #6960
---
 activerecord/CHANGELOG.md                             |  2 ++
 .../lib/active_record/relation/predicate_builder.rb   |  8 ++++++--
 activerecord/test/cases/relation/where_test.rb        | 11 ++++++++++-
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 0d3578f40d..eae36cd258 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,7 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Fix querying with an empty hash *Damien Mathieu*
+
 *   Fix creation of through association models when using `collection=[]`
     on a `has_many :through` association from an unsaved model.
     Fix #7661.
diff --git a/activerecord/lib/active_record/relation/predicate_builder.rb b/activerecord/lib/active_record/relation/predicate_builder.rb
index 36fc08e6ad..263fdce250 100644
--- a/activerecord/lib/active_record/relation/predicate_builder.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder.rb
@@ -10,8 +10,12 @@ module ActiveRecord
           table       = Arel::Table.new(column, default_table.engine)
           association = klass.reflect_on_association(column.to_sym)
 
-          value.each do |k, v|
-            queries.concat expand(association && association.klass, table, k, v)
+          if value.empty?
+            queries.concat ['1 = 2']
+          else
+            value.each do |k, v|
+              queries.concat expand(association && association.klass, table, k, v)
+            end
           end
         else
           column = column.to_s
diff --git a/activerecord/test/cases/relation/where_test.rb b/activerecord/test/cases/relation/where_test.rb
index 3163cf79ad..9c0b139dbf 100644
--- a/activerecord/test/cases/relation/where_test.rb
+++ b/activerecord/test/cases/relation/where_test.rb
@@ -4,10 +4,11 @@ require 'models/price_estimate'
 require 'models/treasure'
 require 'models/post'
 require 'models/comment'
+require 'models/edge'
 
 module ActiveRecord
   class WhereTest < ActiveRecord::TestCase
-    fixtures :posts
+    fixtures :posts, :edges
 
     def test_belongs_to_shallow_where
       author = Author.new
@@ -76,5 +77,13 @@ module ActiveRecord
       post = Post.first
       assert_equal post, Post.where(:posts => { 'id' => post.id }).first
     end
+
+    def test_where_with_table_name_and_empty_hash
+      assert_equal 0, Post.where(:posts => {}).count
+    end
+
+    def test_where_with_empty_hash_and_no_foreign_key
+      assert_equal 0, Edge.where(:sink => {}).count
+    end
   end
 end