Reimplement Fixtures.identify so that it consistently generates identities across ruby versions.

[#2633 state:committed]

Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>

activerecord/lib/active_record/fixtures.rb

@@ -1,6 +1,7 @@
 require 'erb'
 require 'yaml'
 require 'csv'
+require 'zlib'
 require 'active_support/dependencies'
 require 'active_support/test_case'
 
@@ -433,6 +434,7 @@ end
 # Any fixture labeled "DEFAULTS" is safely ignored.
 
 class Fixtures < (RUBY_VERSION < '1.9' ? YAML::Omap : Hash)
+  MAX_ID = 2 ** 31 - 1
   DEFAULT_FILTER_RE = /\.ya?ml$/
 
   @@all_cached_fixtures = {}
@@ -524,11 +526,10 @@ class Fixtures < (RUBY_VERSION < '1.9' ? YAML::Omap : Hash)
     cached_fixtures(connection, table_names)
   end
 
-  # Returns a consistent identifier for +label+. This will always
-  # be a positive integer, and will always be the same for a given
-  # label, assuming the same OS, platform, and version of Ruby.
+  # Returns a consistent, platform-independent identifier for +label+.
+  # Identifiers are positive integers less than 2^32.
   def self.identify(label)
-    label.to_s.hash.abs
+    Zlib.crc32(label.to_s) % MAX_ID
   end
 
   attr_reader :table_name, :name

activerecord/test/cases/fixtures_test.rb

@@ -518,6 +518,11 @@ class FoxyFixturesTest < ActiveRecord::TestCase
     assert_equal(Fixtures.identify(:foo), Fixtures.identify(:foo))
   end
 
+  def test_identifies_consistently
+    assert_equal 1281023246, Fixtures.identify(:ruby)
+    assert_equal 2140105598, Fixtures.identify(:sapphire_2)
+  end
+
   TIMESTAMP_COLUMNS = %w(created_at created_on updated_at updated_on)
 
   def test_populates_timestamp_columns