Do not rely on the column type when quoting infinity

activerecord/lib/active_record/connection_adapters/postgresql/oid/float.rb

@@ -7,6 +7,7 @@ module ActiveRecord
 
           def cast_value(value)
             case value
+            when ::Float then     value
             when 'Infinity' then  ::Float::INFINITY
             when '-Infinity' then -::Float::INFINITY
             when 'NaN' then       ::Float::NAN

activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb

@@ -34,9 +34,7 @@ module ActiveRecord
             else super
             end
           when Float
-            if value.infinite? && column.type == :datetime
-              "'#{value.to_s.downcase}'"
-            elsif value.infinite? || value.nan?
+            if value.infinite? || value.nan?
               "'#{value.to_s}'"
             else
               super

activerecord/test/cases/adapters/postgresql/infinity_test.rb

@@ -0,0 +1,44 @@
+require "cases/helper"
+
+class PostgresqlInfinityTest < ActiveRecord::TestCase
+  class PostgresqlInfinity < ActiveRecord::Base
+  end
+
+  setup do
+    @connection = ActiveRecord::Base.connection
+    @connection.create_table(:postgresql_infinities) do |t|
+      t.float :float
+      t.datetime :datetime
+    end
+  end
+
+  teardown do
+    @connection.execute("DROP TABLE IF EXISTS postgresql_infinities")
+  end
+
+  test "type casting infinity on a float column" do
+    record = PostgresqlInfinity.create!(float: Float::INFINITY)
+    record.reload
+    assert_equal Float::INFINITY, record.float
+  end
+
+  test "update_all with infinity on a float column" do
+    record = PostgresqlInfinity.create!
+    PostgresqlInfinity.update_all(float: Float::INFINITY)
+    record.reload
+    assert_equal Float::INFINITY, record.float
+  end
+
+  test "type casting infinity on a datetime column" do
+    record = PostgresqlInfinity.create!(datetime: Float::INFINITY)
+    record.reload
+    assert_equal Float::INFINITY, record.datetime
+  end
+
+  test "update_all with infinity on a datetime column" do
+    record = PostgresqlInfinity.create!
+    PostgresqlInfinity.update_all(datetime: Float::INFINITY)
+    record.reload
+    assert_equal Float::INFINITY, record.datetime
+  end
+end