Use DateTime::Tiny (and Date::Tiny and Time::Tiny) for improved performance

[ehuelsmann]

The majority of dates don't need calculation (just (de)serialization and user-formatting). DateTime is awfully slow at (de)serializing, although it does it's calculations as correct as possible. For (de)serialization alone, Date(Time)::Tiny are much more suited:

  use Benchmark qw(:all);
  use DateTime;
  use DateTime::Format::Strptime;
  use DateTime::Tiny;


my $format = DateTime::Format::Strptime->new(
      pattern => '%F'
);

timethese(100000, {
   'DateTime' => sub { $format->parse_datetime('2020-01-01'); },
   'DateTime::Tiny' => sub { DateTime::Tiny->from_string('2020-01-01T00:00:00'); }
});


my $dt = $format->parse_datetime('2020-01-01');
my $dtt = DateTime::Tiny->from_string('2020-01-01T00:00:00');


timethese(100000, {
   'DateTime' => sub { $format->format_datetime($dt); },
   'DateTime::Tiny' => sub { $dtt->as_string; }
});

prints:

Benchmark: timing 100000 iterations of DateTime, DateTime::Tiny...
  DateTime:  8 wallclock secs ( 7.88 usr +  0.00 sys =  7.88 CPU) @ 12690.36/s (n=100000)
DateTime::Tiny:  0 wallclock secs ( 0.52 usr +  0.00 sys =  0.52 CPU) @ 192307.69/s (n=100000)
Benchmark: timing 100000 iterations of DateTime, DateTime::Tiny...
  DateTime:  2 wallclock secs ( 1.31 usr +  0.00 sys =  1.31 CPU) @ 76335.88/s (n=100000)
DateTime::Tiny:  0 wallclock secs ( 0.12 usr +  0.00 sys =  0.12 CPU) @ 833333.33/s (n=100000)
            (warning: too few iterations for a reliable count)

Changing "timethese" to "cmpthese", the output is:

                   Rate       DateTime DateTime::Tiny
DateTime        12438/s             --           -94%
DateTime::Tiny 196078/s          1476%             --
            (warning: too few iterations for a reliable count)
                   Rate       DateTime DateTime::Tiny
DateTime        80645/s             --           -91%
DateTime::Tiny 909091/s          1027%             --

[einhverfr]

It should be pretty trivial to do a PGObject::Type::DateTime::Tiny and then inherit from that. The one thing is infinity and -infinity would probably need some special handling. In DateTime these are basically immutable singletons which makes sense.