Refactor microsecond precision to be database agnostic

The various databases don't actually need significantly different
handling for this behavior, and they can achieve it without knowing
about the type of the object.

The old implementation was returning a string, which will cause problems
such as breaking TZ aware attributes, and making it impossible for the
adapters to supply their logic for time objects.

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

@@ -127,7 +127,12 @@ module ActiveRecord
           end
         end
 
-        value.to_s(:db)
+        result = value.to_s(:db)
+        if value.respond_to?(:usec) && value.usec > 0
+          "#{result}.#{sprintf("%06d", value.usec)}"
+        else
+          result
+        end
       end
 
       def prepare_binds_for_database(binds) # :nodoc:

activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb

@@ -29,7 +29,7 @@ module ActiveRecord
 
         limit = column.limit || native_database_types[column.type][:limit]
         spec[:limit]     = limit.inspect if limit
-        spec[:precision] = column.precision.inspect if column.precision
+        spec[:precision] = column.precision.inspect if column.precision && column.precision != 0
         spec[:scale]     = column.scale.inspect if column.scale
 
         default = schema_default(column) if column.has_default?

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -263,18 +263,6 @@ module ActiveRecord
         {}
       end
 
-      # QUOTING ==================================================
-
-      # Quote date/time values for use in SQL input. Includes microseconds
-      # if the value is a Time responding to usec.
-      def quoted_date(value) #:nodoc:
-        if value.acts_like?(:time) && value.respond_to?(:usec)
-          "#{super}.#{sprintf("%06d", value.usec)}"
-        else
-          super
-        end
-      end
-
       # Returns a bind substitution value given a bind +column+
       # NOTE: The column param is currently being used by the sqlserver-adapter
       def substitute_at(column, _unused = 0)
@@ -409,15 +397,15 @@ module ActiveRecord
       protected
 
       def initialize_type_map(m) # :nodoc:
-        register_class_with_limit m, %r(boolean)i,   Type::Boolean
-        register_class_with_limit m, %r(char)i,      Type::String
-        register_class_with_limit m, %r(binary)i,    Type::Binary
-        register_class_with_limit m, %r(text)i,      Type::Text
-        register_class_with_limit m, %r(date)i,      Type::Date
-        register_class_with_limit m, %r(time)i,      Type::Time
-        register_class_with_limit m, %r(datetime)i,  Type::DateTime
-        register_class_with_limit m, %r(float)i,     Type::Float
-        register_class_with_limit m, %r(int)i,       Type::Integer
+        register_class_with_limit m, %r(boolean)i,       Type::Boolean
+        register_class_with_limit m, %r(char)i,          Type::String
+        register_class_with_limit m, %r(binary)i,        Type::Binary
+        register_class_with_limit m, %r(text)i,          Type::Text
+        register_class_with_precision m, %r(date)i,      Type::Date
+        register_class_with_precision m, %r(time)i,      Type::Time
+        register_class_with_precision m, %r(datetime)i,  Type::DateTime
+        register_class_with_limit m, %r(float)i,         Type::Float
+        register_class_with_limit m, %r(int)i,           Type::Integer
 
         m.alias_type %r(blob)i,      'binary'
         m.alias_type %r(clob)i,      'text'
@@ -451,6 +439,13 @@ module ActiveRecord
         end
       end
 
+      def register_class_with_precision(mapping, key, klass) # :nodoc:
+        mapping.register_type(key) do |*args|
+          precision = extract_precision(args.last)
+          klass.new(precision: precision)
+        end
+      end
+
       def extract_scale(sql_type) # :nodoc:
         case sql_type
           when /\((\d+)\)/ then 0

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -712,11 +712,6 @@ module ActiveRecord
         m.alias_type %r(year)i,          'integer'
         m.alias_type %r(bit)i,           'binary'
 
-        m.register_type(%r(datetime)i) do |sql_type|
-          precision = extract_precision(sql_type)
-          MysqlDateTime.new(precision: precision)
-        end
-
         m.register_type(%r(enum)i) do |sql_type|
           limit = sql_type[/^enum\((.+)\)/i, 1]
             .split(',').map{|enum| enum.strip.length - 2}.max
@@ -734,6 +729,14 @@ module ActiveRecord
         end
       end
 
+      def extract_precision(sql_type)
+        if /datetime/ === sql_type
+          super || 0
+        else
+          super
+        end
+      end
+
       def fetch_type_metadata(sql_type, collation = "", extra = "")
         MysqlTypeMetadata.new(super(sql_type), collation: collation, extra: extra, strict: strict_mode?)
       end
@@ -916,14 +919,6 @@ module ActiveRecord
         TableDefinition.new(native_database_types, name, temporary, options, as)
       end
 
-      class MysqlDateTime < Type::DateTime # :nodoc:
-        private
-
-        def has_precision?
-          precision || 0
-        end
-      end
-
       class MysqlString < Type::String # :nodoc:
         def type_cast_for_database(value)
           case value
@@ -945,7 +940,7 @@ module ActiveRecord
       end
 
       def type_classes_with_standard_constructor
-        super.merge(string: MysqlString, date_time: MysqlDateTime)
+        super.merge(string: MysqlString)
       end
     end
   end

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

@@ -5,15 +5,6 @@ module ActiveRecord
         class DateTime < Type::DateTime # :nodoc:
           include Infinity
 
-          def type_cast_for_database(value)
-            if has_precision? && value.acts_like?(:time) && value.year <= 0
-              bce_year = format("%04d", -value.year + 1)
-              super.sub(/^-?\d+/, bce_year) + " BC"
-            else
-              super
-            end
-          end
-
           def cast_value(value)
             if value.is_a?(::String)
               case value

activerecord/lib/active_record/type/date_time.rb

@@ -11,28 +11,25 @@ module ActiveRecord
       end
 
       def type_cast_for_database(value)
-        return super unless value.acts_like?(:time)
-
-        zone_conversion_method = ActiveRecord::Base.default_timezone == :utc ? :getutc : :getlocal
-
-        if value.respond_to?(zone_conversion_method)
-          value = value.send(zone_conversion_method)
+        if precision && value.respond_to?(:usec)
+          number_of_insignificant_digits = 6 - precision
+          round_power = 10 ** number_of_insignificant_digits
+          value = value.change(usec: value.usec / round_power * round_power)
         end
 
-        return value unless has_precision?
+        if value.acts_like?(:time)
+          zone_conversion_method = ActiveRecord::Base.default_timezone == :utc ? :getutc : :getlocal
 
-        result = value.to_s(:db)
-        if value.respond_to?(:usec) && (1..6).cover?(precision)
-          "#{result}.#{sprintf("%0#{precision}d", value.usec / 10 ** (6 - precision))}"
-        else
-          result
+          if value.respond_to?(zone_conversion_method)
+            value = value.send(zone_conversion_method)
+          end
         end
+
+        value
       end
 
       private
 
-      alias has_precision? precision
-
       def cast_value(string)
         return string unless string.is_a?(::String)
         return if string.empty?

activerecord/test/cases/adapters/mysql2/connection_test.rb

@@ -122,11 +122,4 @@ class MysqlConnectionTest < ActiveRecord::TestCase
   ensure
     @connection.execute "DROP TABLE `bar_baz`"
   end
-
-  if mysql_56?
-    def test_quote_time_usec
-      assert_equal "'1970-01-01 00:00:00.000000'", @connection.quote(Time.at(0))
-      assert_equal "'1970-01-01 00:00:00.000000'", @connection.quote(Time.at(0).to_datetime)
-    end
-  end
 end

activerecord/test/cases/adapters/mysql2/datetime_test.rb

@@ -4,15 +4,12 @@ if mysql_56?
   class DateTimeTest < ActiveRecord::TestCase
     self.use_transactional_fixtures = false
 
-    class Foo < ActiveRecord::Base; end
-
-    def test_default_datetime_precision
-      ActiveRecord::Base.connection.create_table(:foos, force: true)
-      ActiveRecord::Base.connection.add_column :foos, :created_at, :datetime
-      ActiveRecord::Base.connection.add_column :foos, :updated_at, :datetime
-      assert_nil activerecord_column_option('foos', 'created_at', 'precision')
+    teardown do
+      ActiveRecord::Base.connection.drop_table(:foos, if_exists: true)
     end
 
+    class Foo < ActiveRecord::Base; end
+
     def test_datetime_data_type_with_precision
       ActiveRecord::Base.connection.create_table(:foos, force: true)
       ActiveRecord::Base.connection.add_column :foos, :created_at, :datetime, precision: 1

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

@@ -27,11 +27,6 @@ module ActiveRecord
           assert_equal "'Infinity'", @conn.quote(infinity)
         end
 
-        def test_quote_time_usec
-          assert_equal "'1970-01-01 00:00:00.000000'", @conn.quote(Time.at(0))
-          assert_equal "'1970-01-01 00:00:00.000000'", @conn.quote(Time.at(0).to_datetime)
-        end
-
         def test_quote_range
           range = "1,2]'; SELECT * FROM users; --".."a"
           type = OID::Range.new(Type::Integer.new, :int8range)

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

@@ -145,10 +145,13 @@ class TimestampTest < ActiveRecord::TestCase
     date = ::Time.utc(2014, 8, 17, 12, 30, 0, 999999)
     Foo.create!(created_at: date, updated_at: date)
     assert foo = Foo.find_by(created_at: date)
+    assert_equal 1, Foo.where(updated_at: date).count
     assert_equal date.to_s, foo.created_at.to_s
     assert_equal date.to_s, foo.updated_at.to_s
     assert_equal 000000, foo.created_at.usec
     assert_equal 999900, foo.updated_at.usec
+  ensure
+    ActiveRecord::Base.connection.drop_table(:foos, if_exists: true)
   end
 
   private

activerecord/test/cases/quoting_test.rb

@@ -46,28 +46,28 @@ module ActiveRecord
 
       def test_quoted_time_utc
         with_timezone_config default: :utc do
-          t = Time.now
+          t = Time.now.change(usec: 0)
           assert_equal t.getutc.to_s(:db), @quoter.quoted_date(t)
         end
       end
 
       def test_quoted_time_local
         with_timezone_config default: :local do
-          t = Time.now
+          t = Time.now.change(usec: 0)
           assert_equal t.getlocal.to_s(:db), @quoter.quoted_date(t)
         end
       end
 
       def test_quoted_time_crazy
         with_timezone_config default: :asdfasdf do
-          t = Time.now
+          t = Time.now.change(usec: 0)
           assert_equal t.getlocal.to_s(:db), @quoter.quoted_date(t)
         end
       end
 
       def test_quoted_datetime_utc
         with_timezone_config default: :utc do
-          t = DateTime.now
+          t = Time.now.change(usec: 0).to_datetime
           assert_equal t.getutc.to_s(:db), @quoter.quoted_date(t)
         end
       end
@@ -76,7 +76,7 @@ module ActiveRecord
       # DateTime doesn't define getlocal, so make sure it does nothing
       def test_quoted_datetime_local
         with_timezone_config default: :local do
-          t = DateTime.now
+          t = Time.now.change(usec: 0).to_datetime
           assert_equal t.to_s(:db), @quoter.quoted_date(t)
         end
       end