Added where option to add_index to support postgresql partial indices

The `add_index` method now supports a `where` option that receives a
string with the partial index criteria.

    add_index(:accounts, :code, :where => "active")

    Generates

    CREATE INDEX index_accounts_on_code ON accounts(code) WHERE active

1 files changed, 12 insertions, 0 deletions

diff --git a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
index e4746d4aa3..447d729e52 100644
--- a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
@@ -21,6 +21,18 @@ class PostgresqlActiveSchemaTest < ActiveRecord::TestCase
     assert_equal %(CREATE DATABASE "aimonetti" ENCODING = 'latin1'), create_database(:aimonetti, :encoding => :latin1)
   end
 
+  def test_add_index
+    # add_index calls index_name_exists? which can't work since execute is stubbed
+    ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.send(:define_method, :index_name_exists?) do |*|
+      false
+    end
+
+    expected = %(CREATE UNIQUE INDEX "index_people_on_last_name" ON "people" ("last_name") WHERE state = 'active')
+    assert_equal expected, add_index(:people, :last_name, :unique => true, :where => "state = 'active'")
+
+    ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.send(:remove_method, :index_name_exists?)
+  end
+
   private
     def method_missing(method_symbol, *arguments)
       ActiveRecord::Base.connection.send(method_symbol, *arguments)