From b514e2767fd72c61cd0f082abd320897cfbe0099 Mon Sep 17 00:00:00 2001
From: Blythe Dunham <blythe@snowgiraffe.com>
Date: Thu, 24 Dec 2009 13:25:09 -0800
Subject: [PATCH 1/5] apply patch

---
 activerecord/lib/active_record.rb                  |    1 +
 activerecord/lib/active_record/base.rb             |    4 ++
 .../connection_adapters/abstract_adapter.rb        |    7 +++
 .../connection_adapters/mysql_adapter.rb           |   12 ++++++
 .../connection_adapters/postgresql_adapter.rb      |    7 +++
 .../connection_adapters/sqlite_adapter.rb          |    7 +++
 activerecord/lib/active_record/locale/en.yml       |    2 +
 .../lib/active_record/unique_constraints.rb        |   24 ++++++++++++
 activerecord/test/cases/adapter_test.rb            |   35 +++++++++++++++++
 activerecord/test/cases/unique_constraints_test.rb |   40 ++++++++++++++++++++
 activerecord/test/models/unique_item.rb            |    2 +
 activerecord/test/schema/schema.rb                 |   15 +++++++
 12 files changed, 156 insertions(+), 0 deletions(-)
 create mode 100644 activerecord/lib/active_record/unique_constraints.rb
 create mode 100644 activerecord/test/cases/unique_constraints_test.rb
 create mode 100644 activerecord/test/models/unique_item.rb

diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index 196b87c..057773a 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -69,6 +69,7 @@ module ActiveRecord
     autoload :Timestamp
     autoload :Transactions
     autoload :Types
+    autoload :UniqueConstraints
     autoload :Validations
   end
 
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 321bba4..da52ec1 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -3117,6 +3117,10 @@ module ActiveRecord #:nodoc:
 
     include Aggregations, Transactions, Reflection, Batches, Calculations, Serialization
 
+    # UniqueConstraints needs to be included after Transactions, because we need #save_with_unique_constraints
+    # to rescue after the transaction has been resolved for postgres.
+    include UniqueConstraints
+
   end
 end
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 8fae26b..832b962 100755
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -198,6 +198,13 @@ module ActiveRecord
         end
       end
 
+      # given an ActiveRecord::RecordNotUnique exception and a table name this returns the index whose
+      # unique constraint was violated, or nil if it can't determine the index
+      def index_for_record_not_unique(not_unique_exception, table_name) #:nodoc:
+        # override in derived class
+        nil
+      end
+
       protected
         def log(sql, name, &block)
           ActiveSupport::Notifications.instrument(:sql, :sql => sql, :name => name, &block)
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index fa28bc6..d83e3d0 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -576,6 +576,18 @@ module ActiveRecord
         where_sql
       end
 
+      def index_for_record_not_unique(exception, table_name) #:nodoc:
+        case exception.message
+        when /Duplicate entry.*for key (\d+)/
+          index_position = $1.to_i
+          # minus two b/c mysql message is one-based + rails excludes primary key index from indexes list
+          indexes(table_name)[index_position - 2]
+        when /Duplicate entry.*for key '(\w+)'/
+          index_name = $1
+          indexes(table_name).detect { |i| i.name == index_name }
+        end
+      end
+
       protected
 
         def translate_exception(exception, message)
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 1d52c5e..70bbbd8 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -929,6 +929,13 @@ module ActiveRecord
         sql << order_columns * ', '
       end
 
+      def index_for_record_not_unique(exception, table_name) #:nodoc:
+        if match = exception.message.match(/unique constraint "(\w+)"/)
+          index_name = match[1]
+          indexes(table_name).detect { |i| i.name == index_name }
+        end
+      end
+
       protected
         # Returns the version of the connected PostgreSQL version.
         def postgresql_version
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
index c9c2892..72dc049 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
@@ -294,6 +294,13 @@ module ActiveRecord
         "VALUES(NULL)"
       end
 
+      def index_for_record_not_unique(exception, table_name) #:nodoc:
+        if match = exception.message.match(/column(?:s)? (.*) (?:is|are) not unique/)
+          index_columns = match[1].split(', ')
+          indexes(table_name).detect { |i| i.columns == index_columns }
+        end
+      end
+
       protected
         def select(sql, name = nil) #:nodoc:
           execute(sql, name).map do |row|
diff --git a/activerecord/lib/active_record/locale/en.yml b/activerecord/lib/active_record/locale/en.yml
index 092f5f0..8144735 100644
--- a/activerecord/lib/active_record/locale/en.yml
+++ b/activerecord/lib/active_record/locale/en.yml
@@ -15,6 +15,8 @@ en:
         too_short: "is too short (minimum is {{count}} characters)"
         wrong_length: "is the wrong length (should be {{count}} characters)"
         taken: "has already been taken"
+        taken_multiple: "has already been taken for {{context}}"
+        taken_generic: "Unique requirement not met"
         not_a_number: "is not a number"
         greater_than: "must be greater than {{count}}"
         greater_than_or_equal_to: "must be greater than or equal to {{count}}"
diff --git a/activerecord/lib/active_record/unique_constraints.rb b/activerecord/lib/active_record/unique_constraints.rb
new file mode 100644
index 0000000..7a17b6a
--- /dev/null
+++ b/activerecord/lib/active_record/unique_constraints.rb
@@ -0,0 +1,24 @@
+module ActiveRecord
+  # See ActiveRecord::Transactions::ClassMethods for documentation.
+  module UniqueConstraints
+    def self.included(base)
+      base.class_eval do
+        alias_method_chain :save, :unique_constraints
+      end
+    end
+
+    def save_with_unique_constraints(perform_validation = true) #:nodoc:
+      save_without_unique_constraints(perform_validation)
+    rescue ActiveRecord::RecordNotUnique => e
+      index = connection.index_for_record_not_unique(e, self.class.table_name)
+      if !index
+        errors[:base] << I18n.translate(:'activerecord.errors.messages.taken_generic')
+      elsif index.columns.size == 1
+        errors.add(index.columns.first, :taken, :value => attributes[index.columns.first])
+      else
+        errors.add(index.columns.first, :taken_multiple, :context => index.columns.slice(1..-1).join('/'), :value => attributes[index.columns.first])
+      end
+      false
+    end
+  end
+end
\ No newline at end of file
diff --git a/activerecord/test/cases/adapter_test.rb b/activerecord/test/cases/adapter_test.rb
index c59be26..4c8f58b 100644
--- a/activerecord/test/cases/adapter_test.rb
+++ b/activerecord/test/cases/adapter_test.rb
@@ -142,4 +142,39 @@ class AdapterTest < ActiveRecord::TestCase
       end
     end
   end
+
+  # tests for db-enforced unique constraints
+  unique_scenarios = {
+    :single         => {:sql => "INSERT INTO unique_items(uniq) VALUES('abc')",
+                        :expected => ['uniq']},
+    :single_named   => {:sql => "INSERT INTO unique_items(uniq_named) VALUES('abc')",
+                        :expected => ['uniq_named']},
+    :multiple       => {:sql => "INSERT INTO unique_items(uniq_1, uniq_2, uniq_3) VALUES('a', 'b', 'c')",
+                        :expected => ['uniq_1', 'uniq_2', 'uniq_3']},
+    :multiple_named => {:sql => "INSERT INTO unique_items(uniq_1_named, uniq_2_named, uniq_3_named) VALUES('a', 'b', 'c')",
+                        :expected => ['uniq_1_named', 'uniq_2_named', 'uniq_3_named']}
+  }
+  unique_scenarios.each do |name, data|
+    test "finds index for unique constraint #{name}" do
+      @connection.execute data[:sql]
+      exception = get_exception(ActiveRecord::RecordNotUnique) do
+        @connection.execute data[:sql]
+      end
+      # postgres can't query indexes until transaction is rolled back
+      @connection.rollback_db_transaction if current_adapter?(:PostgreSQLAdapter)
+      assert_equal data[:expected], @connection.index_for_record_not_unique(exception, 'unique_items').columns
+    end
+  end
+
+  protected
+
+  def get_exception(expected_exception)
+    begin
+      yield
+    rescue expected_exception => e
+      e
+    else
+      flunk "Expected #{expected_exception} exception"
+    end
+  end
 end
diff --git a/activerecord/test/cases/unique_constraints_test.rb b/activerecord/test/cases/unique_constraints_test.rb
new file mode 100644
index 0000000..92ba6d8
--- /dev/null
+++ b/activerecord/test/cases/unique_constraints_test.rb
@@ -0,0 +1,40 @@
+require "cases/helper"
+require 'models/unique_item'
+
+class UniquenessValidationTest < ActiveRecord::TestCase
+
+  def test_validate_uniqueness_on_create
+    valid_item = UniqueItem.create!(:uniq => 'abc')
+    invalid_item = UniqueItem.create(:uniq => 'abc')
+    assert_equal ["has already been taken"], invalid_item.errors[:uniq]
+  end
+
+  def test_validate_uniqueness_on_save
+    item_1 = UniqueItem.create!(:uniq => 'abc')
+    item_2 = UniqueItem.create!(:uniq => 'xyz')
+    item_2.uniq = item_1.uniq
+    item_2.save
+    assert_equal ["has already been taken"], item_2.errors[:uniq]
+  end
+
+  def test_validate_uniqueness_on_update
+    item_1 = UniqueItem.create!(:uniq => 'abc')
+    item_2 = UniqueItem.create!(:uniq => 'xyz')
+    item_2.update_attributes(:uniq => item_1.uniq)
+    assert_equal ["has already been taken"], item_2.errors[:uniq]
+  end
+
+  def test_validate_uniqueness_multiple
+    valid_item = UniqueItem.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
+    invalid_item = UniqueItem.create(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
+    assert_equal ["has already been taken for uniq_2/uniq_3"], invalid_item.errors[:uniq_1]
+  end
+
+  def test_validate_uniqueness_generic
+    ActiveRecord::Base.connection.expects(:index_for_record_not_unique).returns(nil)
+    valid_item = UniqueItem.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
+    invalid_item = UniqueItem.create(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
+    assert_equal ["Unique requirement not met"], invalid_item.errors[:base]
+  end
+
+end
\ No newline at end of file
diff --git a/activerecord/test/models/unique_item.rb b/activerecord/test/models/unique_item.rb
new file mode 100644
index 0000000..3c6f6f0
--- /dev/null
+++ b/activerecord/test/models/unique_item.rb
@@ -0,0 +1,2 @@
+class UniqueItem < ActiveRecord::Base
+end
\ No newline at end of file
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 0dd9da4..1aea762 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -532,6 +532,21 @@ ActiveRecord::Schema.define do
     t.string :title
   end
 
+  create_table :unique_items, :force => true do |t|
+    t.string :uniq
+    t.string :uniq_1
+    t.string :uniq_2
+    t.string :uniq_3
+    t.string :uniq_named
+    t.string :uniq_1_named
+    t.string :uniq_2_named
+    t.string :uniq_3_named
+  end
+  add_index :unique_items, [:uniq], :unique => true
+  add_index :unique_items, [:uniq_named], :unique => true, :name => 'unique_named_single_index'
+  add_index :unique_items, [:uniq_1, :uniq_2, :uniq_3], :unique => true
+  add_index :unique_items, [:uniq_1_named, :uniq_2_named, :uniq_3_named], :unique => true, :name => 'unique_named_multiple_index'
+
   except 'SQLite' do
     # fk_test_has_fk should be before fk_test_has_pk
     create_table :fk_test_has_fk, :force => true do |t|
-- 
1.6.5


From 72b933e62bcd218d0da4443143437db1be86d88f Mon Sep 17 00:00:00 2001
From: Blythe Dunham <blythe@snowgiraffe.com>
Date: Thu, 24 Dec 2009 15:00:58 -0800
Subject: [PATCH 2/5] Add Unique Key violation errors to activerecord object for save!

---
 .../lib/active_record/unique_constraints.rb        |   31 ++++++++++++++++----
 activerecord/test/cases/unique_constraints_test.rb |   31 +++++++++++++++++++-
 2 files changed, 55 insertions(+), 7 deletions(-)

diff --git a/activerecord/lib/active_record/unique_constraints.rb b/activerecord/lib/active_record/unique_constraints.rb
index 7a17b6a..05b3dea 100644
--- a/activerecord/lib/active_record/unique_constraints.rb
+++ b/activerecord/lib/active_record/unique_constraints.rb
@@ -1,16 +1,36 @@
 module ActiveRecord
+  class RecordInvalidNotUnique < RecordInvalid; end
+
   # See ActiveRecord::Transactions::ClassMethods for documentation.
   module UniqueConstraints
     def self.included(base)
       base.class_eval do
-        alias_method_chain :save, :unique_constraints
+        alias_method_chain :save,  :unique_constraints
+        alias_method_chain :save!, :unique_constraints
       end
     end
 
-    def save_with_unique_constraints(perform_validation = true) #:nodoc:
-      save_without_unique_constraints(perform_validation)
-    rescue ActiveRecord::RecordNotUnique => e
-      index = connection.index_for_record_not_unique(e, self.class.table_name)
+    def save_with_unique_constraints(*args)#:nodoc:
+      save_without_unique_constraints(*args)
+    rescue RecordNotUnique => e
+      rescue_unique_key_violation(e)
+      false
+    end
+
+    def save_with_unique_constraints!(*args)#:nodoc:
+      save_without_unique_constraints!(*args)
+    rescue RecordNotUnique => e
+      rescue_unique_key_violation(e)
+      raise RecordInvalidNotUnique.new(self)
+    end
+
+    protected
+    # Convert the RecordNotUnique exception into an error message
+    # return true if the violation occurred on column(s) explictly declared to be
+    # handled
+    def rescue_unique_key_violation(e)#:nodoc:
+      index = connection.index_for_record_not_unique(e.original_exception, self.class.table_name)
+
       if !index
         errors[:base] << I18n.translate(:'activerecord.errors.messages.taken_generic')
       elsif index.columns.size == 1
@@ -18,7 +38,6 @@ module ActiveRecord
       else
         errors.add(index.columns.first, :taken_multiple, :context => index.columns.slice(1..-1).join('/'), :value => attributes[index.columns.first])
       end
-      false
     end
   end
 end
\ No newline at end of file
diff --git a/activerecord/test/cases/unique_constraints_test.rb b/activerecord/test/cases/unique_constraints_test.rb
index 92ba6d8..3416c0e 100644
--- a/activerecord/test/cases/unique_constraints_test.rb
+++ b/activerecord/test/cases/unique_constraints_test.rb
@@ -9,14 +9,27 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert_equal ["has already been taken"], invalid_item.errors[:uniq]
   end
 
+  def test_validate_uniqueness_on_create!
+    valid_item = UniqueItem.create!(:uniq => 'abc')
+    assert_raises_record_invalid{ UniqueItem.create!(:uniq => 'abc') }
+  end
+
   def test_validate_uniqueness_on_save
     item_1 = UniqueItem.create!(:uniq => 'abc')
     item_2 = UniqueItem.create!(:uniq => 'xyz')
     item_2.uniq = item_1.uniq
-    item_2.save
+    assert !item_2.save
     assert_equal ["has already been taken"], item_2.errors[:uniq]
   end
 
+  def test_validate_uniqueness_on_save!
+    item_1 = UniqueItem.create!(:uniq => 'abc')
+    item_2 = UniqueItem.create!(:uniq => 'xyz')
+    item_2.uniq = item_1.uniq
+    assert_raises_record_invalid{ item_2.save! }
+    assert_equal(["has already been taken"], item_2.errors[:uniq])
+  end
+
   def test_validate_uniqueness_on_update
     item_1 = UniqueItem.create!(:uniq => 'abc')
     item_2 = UniqueItem.create!(:uniq => 'xyz')
@@ -24,12 +37,24 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert_equal ["has already been taken"], item_2.errors[:uniq]
   end
 
+  def test_validate_uniqueness_on_update_attributes!
+    item_1 = UniqueItem.create!(:uniq => 'abc')
+    item_2 = UniqueItem.create!(:uniq => 'xyz')
+    assert_raises_record_invalid{ item_2.update_attributes!( :uniq => 'abc') }
+    assert_equal(["has already been taken"], item_2.errors[:uniq])
+  end
+
   def test_validate_uniqueness_multiple
     valid_item = UniqueItem.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
     invalid_item = UniqueItem.create(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
     assert_equal ["has already been taken for uniq_2/uniq_3"], invalid_item.errors[:uniq_1]
   end
 
+  def test_validate_uniqueness_multiple!
+    valid_item = UniqueItem.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
+    assert_raises_record_invalid { UniqueItem.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c') }
+  end
+
   def test_validate_uniqueness_generic
     ActiveRecord::Base.connection.expects(:index_for_record_not_unique).returns(nil)
     valid_item = UniqueItem.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
@@ -37,4 +62,8 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert_equal ["Unique requirement not met"], invalid_item.errors[:base]
   end
 
+  protected
+  def assert_raises_record_invalid(&block)
+    assert_raises(ActiveRecord::RecordInvalidNotUnique, &block)
+  end
 end
\ No newline at end of file
-- 
1.6.5


From a08841e0c9add6b4feffa7dbf7cc4566f53cc622 Mon Sep 17 00:00:00 2001
From: Blythe Dunham <blythe@snowgiraffe.com>
Date: Thu, 24 Dec 2009 15:15:28 -0800
Subject: [PATCH 3/5] rename rescue method

---
 .../lib/active_record/unique_constraints.rb        |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/activerecord/lib/active_record/unique_constraints.rb b/activerecord/lib/active_record/unique_constraints.rb
index 05b3dea..6ed0c50 100644
--- a/activerecord/lib/active_record/unique_constraints.rb
+++ b/activerecord/lib/active_record/unique_constraints.rb
@@ -13,14 +13,14 @@ module ActiveRecord
     def save_with_unique_constraints(*args)#:nodoc:
       save_without_unique_constraints(*args)
     rescue RecordNotUnique => e
-      rescue_unique_key_violation(e)
+      add_record_not_unique_errors(e)
       false
     end
 
     def save_with_unique_constraints!(*args)#:nodoc:
       save_without_unique_constraints!(*args)
     rescue RecordNotUnique => e
-      rescue_unique_key_violation(e)
+      add_record_not_unique_errors(e)
       raise RecordInvalidNotUnique.new(self)
     end
 
@@ -28,7 +28,7 @@ module ActiveRecord
     # Convert the RecordNotUnique exception into an error message
     # return true if the violation occurred on column(s) explictly declared to be
     # handled
-    def rescue_unique_key_violation(e)#:nodoc:
+    def add_record_not_unique_errors(e)#:nodoc:
       index = connection.index_for_record_not_unique(e.original_exception, self.class.table_name)
 
       if !index
-- 
1.6.5


From b96feae6eacb28077d41614d6a00917274622209 Mon Sep 17 00:00:00 2001
From: Blythe Dunham <blythe@snowgiraffe.com>
Date: Thu, 24 Dec 2009 15:17:30 -0800
Subject: [PATCH 4/5] reraise RecordNotUnique

---
 .../lib/active_record/unique_constraints.rb        |    3 +--
 activerecord/test/cases/unique_constraints_test.rb |    2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/activerecord/lib/active_record/unique_constraints.rb b/activerecord/lib/active_record/unique_constraints.rb
index 6ed0c50..d9f2da4 100644
--- a/activerecord/lib/active_record/unique_constraints.rb
+++ b/activerecord/lib/active_record/unique_constraints.rb
@@ -1,5 +1,4 @@
 module ActiveRecord
-  class RecordInvalidNotUnique < RecordInvalid; end
 
   # See ActiveRecord::Transactions::ClassMethods for documentation.
   module UniqueConstraints
@@ -21,7 +20,7 @@ module ActiveRecord
       save_without_unique_constraints!(*args)
     rescue RecordNotUnique => e
       add_record_not_unique_errors(e)
-      raise RecordInvalidNotUnique.new(self)
+      raise e
     end
 
     protected
diff --git a/activerecord/test/cases/unique_constraints_test.rb b/activerecord/test/cases/unique_constraints_test.rb
index 3416c0e..2e27d1a 100644
--- a/activerecord/test/cases/unique_constraints_test.rb
+++ b/activerecord/test/cases/unique_constraints_test.rb
@@ -64,6 +64,6 @@ class UniquenessValidationTest < ActiveRecord::TestCase
 
   protected
   def assert_raises_record_invalid(&block)
-    assert_raises(ActiveRecord::RecordInvalidNotUnique, &block)
+    assert_raises(ActiveRecord::RecordNotUnique, &block)
   end
 end
\ No newline at end of file
-- 
1.6.5


From 1777829e922330ca2e0a6b645b95990ebdb9c957 Mon Sep 17 00:00:00 2001
From: Blythe Dunham <blythe@snowgiraffe.com>
Date: Thu, 24 Dec 2009 20:31:03 -0800
Subject: [PATCH 5/5] Customization options and validation consistency for validates_unqueness_of using db constraints

---
 .../lib/active_record/unique_constraints.rb        |  106 +++++++++++++++++++-
 activerecord/test/cases/unique_constraints_test.rb |   88 +++++++++++++++--
 activerecord/test/models/unique_item.rb            |   17 +++-
 3 files changed, 198 insertions(+), 13 deletions(-)

diff --git a/activerecord/lib/active_record/unique_constraints.rb b/activerecord/lib/active_record/unique_constraints.rb
index d9f2da4..d8bbb96 100644
--- a/activerecord/lib/active_record/unique_constraints.rb
+++ b/activerecord/lib/active_record/unique_constraints.rb
@@ -1,14 +1,101 @@
 module ActiveRecord
 
+  class RecordInvalidNotUnique < RecordInvalid; end
+  VALID_HANDLE_UNIQUE_KEY_OPTIONS = [:scope, :field_name, :message]
+  
   # See ActiveRecord::Transactions::ClassMethods for documentation.
   module UniqueConstraints
-    def self.included(base)
+    def self.included(base)#:nodoc:
       base.class_eval do
+        extend ClassMethods
         alias_method_chain :save,  :unique_constraints
         alias_method_chain :save!, :unique_constraints
       end
     end
 
+    module ClassMethods
+      def self.extended(base)#:nodoc:
+        base.class_eval do
+          class << self
+            alias_method_chain :validates_uniqueness_of,      :unique_key
+            alias_method       :handle_unique_key_violations, :handle_unique_key_violation
+          end
+
+          class_inheritable_hash :unique_key_validation_options
+          self.unique_key_validation_options = {}
+        end
+      end
+
+      # Specify custom error messages to use when converting database unique key violation errors 
+      # into active record errors.
+      # For consistency with standard validation exceptions raised by save!, explicitly declared validations
+      # convert database RecordNotUnique to RecordInvalid derived exceptions.
+      #
+      # === Options
+      # <tt>:message</tt> - Specifies a custom error message (default is: "has already been taken").
+      # <tt>:scope</tt> -  One or more columns by which to limit the scope of the uniqueness constraint.
+      #
+      # === Examples
+      #    # The following are equivalent
+      #    class User
+      #      handles_unique_key_violation :name, :message => 'already exists'
+      #      validates_uniqueness_of :user, :message => 'already exists', :lazy => true, 
+      #    end
+      #
+      #    # Convert all violations for all active record classes
+      #    ActiveRecord::Base.handle_unique_key_violations
+      def handle_unique_key_violation(*attr_names)
+        options = attr_names.extract_options!
+        options.symbolize_keys!
+        options.assert_valid_keys(VALID_HANDLE_UNIQUE_KEY_OPTIONS)
+
+        # when blank, convert all violations
+        attr_names << :all if attr_names.none?
+
+        attr_names.each do |name|
+          self.unique_key_validation_options[ name.to_sym ] = if name.to_sym == :all
+            { :message => options[:message], :field_name => nil, :columns => [] }
+          else
+            options.reverse_merge(
+              :field_name => name.to_s,
+              :columns => [name.to_s].
+              concat( (options[:scope]||[]).collect(&:to_s) ).uniq.sort
+            )
+          end
+        end
+      end
+
+      # <tt>:lazy</tt>Reactively convert database unique key violations to active record error messages
+      # instead of proactively querying the database
+      #
+      # === Options
+      # <tt>:lazy</tt> option when set to true, the proactive validations are skipped
+      # Only the <tt>:scope</tt> and <tt>:message</tt> options are valid with <tt>:lazy => true</tt>
+      # === Examples
+      #    # The following are equivalent
+      #    class User
+      #      handles_unique_key_violation :name, :message => 'already exists'
+      #      validates_uniqueness_of :user, :message => 'already exists', :lazy => true, 
+      #    end
+      #
+      #    # Convert all violations for all active record classes
+      #    ActiveRecord::Base.validates_uniqueness_of :lazy => true
+      def validates_uniqueness_of_with_unique_key(*attr_names)
+        configuration = attr_names.extract_options!
+        configuration.symbolize_keys!
+
+        if configuration.delete(:lazy)
+          configuration.assert_valid_keys(VALID_HANDLE_UNIQUE_KEY_OPTIONS)
+        else
+          validates_uniqueness_of_without_unique_key(*(attr_names + [configuration]))
+        end
+  
+        attr_names << configuration.reject{|k, v| !VALID_HANDLE_UNIQUE_KEY_OPTIONS.include?(k) }
+        handle_unique_key_violation(*attr_names)
+      end
+  
+    end
+
     def save_with_unique_constraints(*args)#:nodoc:
       save_without_unique_constraints(*args)
     rescue RecordNotUnique => e
@@ -19,24 +106,37 @@ module ActiveRecord
     def save_with_unique_constraints!(*args)#:nodoc:
       save_without_unique_constraints!(*args)
     rescue RecordNotUnique => e
-      add_record_not_unique_errors(e)
+      raise RecordInvalidNotUnique.new( self ) if add_record_not_unique_errors( e )
       raise e
     end
 
     protected
+
     # Convert the RecordNotUnique exception into an error message
     # return true if the violation occurred on column(s) explictly declared to be
     # handled
     def add_record_not_unique_errors(e)#:nodoc:
       index = connection.index_for_record_not_unique(e.original_exception, self.class.table_name)
 
-      if !index
+      # If an index is found, find a the configuration for validates_uniqueness_of
+      # Or use :all (global) options if specified
+      record_not_found_options = unique_key_validation_options.values.detect{ |v| 
+        v[:columns] == index.columns.sort || v[:field_name] == index.columns.first
+      } if index
+      record_not_found_options ||= unique_key_validation_options[:all]
+
+      if record_not_found_options && record_not_found_options[:message]
+        column_name = record_not_found_options[:field_name] || index.columns.first
+        errors.add(column_name,record_not_found_options[:message], :value => column_name)
+      elsif !index
         errors[:base] << I18n.translate(:'activerecord.errors.messages.taken_generic')
       elsif index.columns.size == 1
         errors.add(index.columns.first, :taken, :value => attributes[index.columns.first])
       else
         errors.add(index.columns.first, :taken_multiple, :context => index.columns.slice(1..-1).join('/'), :value => attributes[index.columns.first])
       end
+
+      !!record_not_found_options
     end
   end
 end
\ No newline at end of file
diff --git a/activerecord/test/cases/unique_constraints_test.rb b/activerecord/test/cases/unique_constraints_test.rb
index 2e27d1a..46c0c17 100644
--- a/activerecord/test/cases/unique_constraints_test.rb
+++ b/activerecord/test/cases/unique_constraints_test.rb
@@ -1,6 +1,5 @@
 require "cases/helper"
 require 'models/unique_item'
-
 class UniquenessValidationTest < ActiveRecord::TestCase
 
   def test_validate_uniqueness_on_create
@@ -11,7 +10,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
 
   def test_validate_uniqueness_on_create!
     valid_item = UniqueItem.create!(:uniq => 'abc')
-    assert_raises_record_invalid{ UniqueItem.create!(:uniq => 'abc') }
+    assert_raises_record_not_unique{ UniqueItem.create!(:uniq => 'abc') }
   end
 
   def test_validate_uniqueness_on_save
@@ -24,9 +23,8 @@ class UniquenessValidationTest < ActiveRecord::TestCase
 
   def test_validate_uniqueness_on_save!
     item_1 = UniqueItem.create!(:uniq => 'abc')
-    item_2 = UniqueItem.create!(:uniq => 'xyz')
-    item_2.uniq = item_1.uniq
-    assert_raises_record_invalid{ item_2.save! }
+    item_2 = UniqueItem.new(:uniq => 'abc')
+    assert_raises_record_not_unique{ item_2.save! }
     assert_equal(["has already been taken"], item_2.errors[:uniq])
   end
 
@@ -37,10 +35,10 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert_equal ["has already been taken"], item_2.errors[:uniq]
   end
 
-  def test_validate_uniqueness_on_update_attributes!
+  def test_validate_uniqueness_on_update!
     item_1 = UniqueItem.create!(:uniq => 'abc')
     item_2 = UniqueItem.create!(:uniq => 'xyz')
-    assert_raises_record_invalid{ item_2.update_attributes!( :uniq => 'abc') }
+    assert_raises_record_not_unique{ item_2.update_attributes!( :uniq => 'abc') }
     assert_equal(["has already been taken"], item_2.errors[:uniq])
   end
 
@@ -52,7 +50,73 @@ class UniquenessValidationTest < ActiveRecord::TestCase
 
   def test_validate_uniqueness_multiple!
     valid_item = UniqueItem.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
-    assert_raises_record_invalid { UniqueItem.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c') }
+    assert_raises_record_not_unique { UniqueItem.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c') }
+  end
+
+  def test_validate_uniqueness_multiple_with_custom_translated_validation_message
+    UniqueItemWithValidation.validates_uniqueness_of :uniq_1, :message => :invalid, :lazy => true, :scope => %w(uniq_2 uniq_3)
+    valid_item = UniqueItemWithValidation.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
+    invalid_item = UniqueItemWithValidation.create(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
+    assert_equal ["is invalid"], invalid_item.errors[:uniq_1]
+  end
+
+  def test_validate_uniqueness_raises_record_invalid_with_custom_error_message
+    UniqueItemWithValidation.validates_uniqueness_of :uniq, :message => 'is really taken.', :lazy => true
+    item_1 = UniqueItemWithValidation.create!(:uniq => 'abc')
+    item_2 = UniqueItemWithValidation.create!(:uniq => 'xyz')
+    item_2.uniq = item_1.uniq
+    assert_raises_record_invalid{ item_2.save! }
+    assert_equal ['is really taken.'], item_2.errors[:uniq]
+  end
+
+  def test_raises_record_not_unique_violation_without_declaring_validates_uniqueness_of(message)
+    UniqueItemWithValidation.validates_uniqueness_of :uniq, :message => 'is really taken.', :lazy => true
+    item_1 = UniqueItemWithValidation.create!(:uniq_named => 'abc')
+    item_2 = UniqueItemWithValidation.create!(:uniq_named => 'xyz')
+    item_2.uniq_named = item_1.uniq_named
+    assert_raises_record_not_unique{ item_2.save! }
+    assert_equal ["has already been taken"], item_2.errors[:uniq_named]
+  end
+
+  def test_standard_validates_uniqueness_of_save_failure_is_handled
+    # Standard validation succeeds
+    UniqueItemWithStandardValidation.expects(:exists?).returns(false)
+    valid_item = UniqueItem.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
+    invalid_item = UniqueItemWithStandardValidation.new(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
+    assert_raises_record_invalid{ invalid_item.save! }
+    assert_equal ["standard validation"], invalid_item.errors[:uniq_1]
+  end
+
+  def test_standard_validates_uniqueness_of_create_failure_is_handled
+    # Standard validation succeeds
+    UniqueItemWithStandardValidation.expects(:exists?).returns(false)
+    item_1 = UniqueItem.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c')
+    assert_raises_record_invalid { 
+      UniqueItemWithStandardValidation.create!(:uniq_1 => 'a', :uniq_2 => 'b', :uniq_3 => 'c') 
+    }
+  end
+
+  def test_validate_uniqueness_of_all_on_save!
+    assert(UniqueItemWithAllValidation.unique_key_validation_options.has_key?(:all))
+    item_1 = UniqueItemWithAllValidation.create!(:uniq_named => 'abc')
+    item_2 = UniqueItemWithAllValidation.create!(:uniq_named => 'xyz')
+    item_2.uniq_named = item_1.uniq_named
+    assert_raises_record_invalid{ item_2.save! }
+    assert_equal ['all validation messages'], item_2.errors[:uniq_named]
+  end
+
+  def test_validate_uniqueness_of_invalid_options
+    assert_raises(ArgumentError) {
+      UniqueItem.validates_uniqueness_of :uniq, :allow_nil => false, :lazy => true
+    }
+
+    assert_raises(ArgumentError) {
+      UniqueItem.handle_unique_key_violations :uniq, :message => 'goo', :if => lambda{ true }, :lazy => true
+    }
+
+    assert_raises(ArgumentError) {
+      UniqueItem.handle_unique_key_violation  :allow_nil => false, :lazy => true
+    }
   end
 
   def test_validate_uniqueness_generic
@@ -63,7 +127,13 @@ class UniquenessValidationTest < ActiveRecord::TestCase
   end
 
   protected
-  def assert_raises_record_invalid(&block)
+
+  def assert_raises_record_not_unique(&block)
     assert_raises(ActiveRecord::RecordNotUnique, &block)
   end
+
+  def assert_raises_record_invalid(&block)
+    assert_raises(ActiveRecord::RecordInvalidNotUnique, &block)
+  end
+
 end
\ No newline at end of file
diff --git a/activerecord/test/models/unique_item.rb b/activerecord/test/models/unique_item.rb
index 3c6f6f0..d34a40a 100644
--- a/activerecord/test/models/unique_item.rb
+++ b/activerecord/test/models/unique_item.rb
@@ -1,2 +1,17 @@
 class UniqueItem < ActiveRecord::Base
-end
\ No newline at end of file
+end
+
+class UniqueItemWithValidation < ActiveRecord::Base
+  set_table_name 'unique_items'
+  validates_uniqueness_of :uniq, :message => :invalid, :lazy => true
+end
+
+class UniqueItemWithAllValidation < ActiveRecord::Base
+  set_table_name 'unique_items'
+  validates_uniqueness_of :message => 'all validation messages'
+end
+
+class UniqueItemWithStandardValidation < ActiveRecord::Base
+  set_table_name 'unique_items'
+  validates_uniqueness_of :uniq_1, :message => 'standard validation', :scope => [:uniq_2, :uniq_3 ], :allow_nil => true
+end
-- 
1.6.5