pg, fix Infinity and NaN values conversion.

Before this patch `Infinity`, `-Infinity` and `Nan` were read as `0`.

activerecord/CHANGELOG.md

@@ -1,3 +1,18 @@
+*   Fix `PostgreSQLAdapter::OID::Float#type_cast` to convert Infinity and
+    NaN PostgreSQL values into a native Ruby `Float::INFINITY` and `Float::NAN`
+
+    Example:
+
+        # Before
+        Point.create(value: 1.0/0)
+        Point.last.value # => 0.0
+
+        # After
+        Point.create(value: 1.0/0)
+        Point.last.value # => Infinity
+
+    *Innokenty Mikhailov*
+
 *   Allow the PostgreSQL adapter to handle bigserial pk types again.
 
     Fixes #10410.

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

@@ -249,9 +249,14 @@ class Float < Type
           def type; :float end
 
           def type_cast(value)
-            return if value.nil?
-
-            value.to_f
+            case value
+              when nil;         nil
+              when 'Infinity';  ::Float::INFINITY
+              when '-Infinity'; -::Float::INFINITY
+              when 'NaN';       ::Float::NAN
+            else
+              value.to_f
+            end
           end
         end
 

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

@@ -50,7 +50,11 @@ def setup
     @second_money = PostgresqlMoney.find(2)
 
     @connection.execute("INSERT INTO postgresql_numbers (id, single, double) VALUES (1, 123.456, 123456.789)")
+    @connection.execute("INSERT INTO postgresql_numbers (id, single, double) VALUES (2, '-Infinity', 'Infinity')")
+    @connection.execute("INSERT INTO postgresql_numbers (id, single, double) VALUES (3, 123.456, 'NaN')")
     @first_number = PostgresqlNumber.find(1)
+    @second_number = PostgresqlNumber.find(2)
+    @third_number = PostgresqlNumber.find(3)
 
     @connection.execute("INSERT INTO postgresql_times (id, time_interval, scaled_time_interval) VALUES (1, '1 year 2 days ago', '3 weeks ago')")
     @first_time = PostgresqlTime.find(1)
@@ -154,6 +158,9 @@ def test_update_tsvector
   def test_number_values
     assert_equal 123.456, @first_number.single
     assert_equal 123456.789, @first_number.double
+    assert_equal -::Float::INFINITY, @second_number.single
+    assert_equal ::Float::INFINITY, @second_number.double
+    assert_same ::Float::NAN, @third_number.double
   end
 
   def test_time_values