msgpack: support datetime extended type

Tarantool supports datetime type since version 2.10.0 [1]. This patch
introduced the support of Tarantool datetime type in msgpack decoders
and encoders.

Tarantool datetime objects are decoded to `tarantool.Datetime` type.
`tarantool.Datetime` may be encoded to Tarantool datetime objects.

`tarantool.Datetime` stores data in a `pandas.Timestamp` object. You can
create `tarantool.Datetime` objects either from msgpack data or by using
the same API as in Tarantool:

```
dt1 = tarantool.Datetime(year=2022, month=8, day=31,
                         hour=18, minute=7, sec=54,
                         nsec=308543321)

dt2 = tarantool.Datetime(timestamp=1661969274)

dt3 = tarantool.Datetime(timestamp=1661969274, nsec=308543321)
```

`tarantool.Datetime` exposes `year`, `month`, `day`, `hour`, `minute`,
`sec`, `nsec` and `timestamp` properties if you need to convert
`tarantool.Datetime` to any other kind of datetime object:

```
pdt = pandas.Timestamp(year=dt.year, month=dt.month, day=dt.day,
                       hour=dt.hour, minute=dt.minute, second=dt.sec,
                       microsecond=(dt.nsec // 1000),
                       nanosecond=(dt.nsec % 1000))
```

`pandas.Timestamp` was chosen to store data because it could be used
to store both nanoseconds and timezone information. In-build Python
`datetime.datetime` supports microseconds at most, `numpy.datetime64` do
not support timezones.

Tarantool datetime interval type is planned to be stored in custom
type `tarantool.Interval` and we'll need a way to support arithmetic
between datetime and interval. This is the main reason we use custom
class instead of plain `pandas.Timestamp`. It is also hard to implement
Tarantool-compatible timezones with full conversion support without
custom classes.

This patch does not yet introduce the support of timezones in datetime.

1. tarantool/tarantool#5941
2. https://pandas.pydata.org/docs/reference/api/pandas.Timestamp.html

Part of #204

CHANGELOG.md

@@ -9,6 +9,35 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Decimal type support (#203).
 - UUID type support (#202).
+- Datetime type support and tarantool.Datetime type (#204).
+
+  Tarantool datetime objects are decoded to `tarantool.Datetime`
+  type. `tarantool.Datetime` may be encoded to Tarantool datetime
+  objects.
+
+  You can create `tarantool.Datetime` objects either from msgpack
+  data or by using the same API as in Tarantool:
+
+  ```python
+  dt1 = tarantool.Datetime(year=2022, month=8, day=31,
+                           hour=18, minute=7, sec=54,
+                           nsec=308543321)
+
+  dt2 = tarantool.Datetime(timestamp=1661969274)
+
+  dt3 = tarantool.Datetime(timestamp=1661969274, nsec=308543321)
+  ```
+
+  `tarantool.Datetime` exposes `year`, `month`, `day`, `hour`,
+  `minute`, `sec`, `nsec` and `timestamp` properties if you need
+  to convert `tarantool.Datetime` to any other kind of datetime object:
+
+  ```python
+  pdt = pandas.Timestamp(year=dt.year, month=dt.month, day=dt.day,
+                         hour=dt.hour, minute=dt.minute, second=dt.sec,
+                         microsecond=(dt.nsec // 1000),
+                         nanosecond=(dt.nsec % 1000))
+  ```
 
 ### Changed
 - Bump msgpack requirement to 1.0.4 (PR #223).

requirements.txt

@@ -1 +1,2 @@
 msgpack>=1.0.4
+pandas

tarantool/__init__.py

@@ -32,6 +32,10 @@
     ENCODING_DEFAULT,
 )
 
+from tarantool.msgpack_ext.types.datetime import (
+    Datetime,
+)
+
 __version__ = "0.9.0"
 
 
@@ -91,7 +95,7 @@ def connectmesh(addrs=({'host': 'localhost', 'port': 3301},), user=None,
 
 __all__ = ['connect', 'Connection', 'connectmesh', 'MeshConnection', 'Schema',
            'Error', 'DatabaseError', 'NetworkError', 'NetworkWarning',
-           'SchemaError', 'dbapi']
+           'SchemaError', 'dbapi', 'Datetime']
 
 # ConnectionPool is supported only for Python 3.7 or newer.
 if sys.version_info.major >= 3 and sys.version_info.minor >= 7:

tarantool/msgpack_ext/datetime.py

@@ -0,0 +1,9 @@
+from tarantool.msgpack_ext.types.datetime import Datetime
+
+EXT_ID = 4
+
+def encode(obj):
+    return obj.msgpack_encode()
+
+def decode(data):
+    return Datetime(data)

tarantool/msgpack_ext/packer.py

@@ -2,12 +2,16 @@
 from uuid import UUID
 from msgpack import ExtType
 
+from tarantool.msgpack_ext.types.datetime import Datetime
+
 import tarantool.msgpack_ext.decimal as ext_decimal
 import tarantool.msgpack_ext.uuid as ext_uuid
+import tarantool.msgpack_ext.datetime as ext_datetime
 
 encoders = [
-    {'type': Decimal, 'ext': ext_decimal},
-    {'type': UUID,    'ext': ext_uuid   },
+    {'type': Decimal,  'ext': ext_decimal },
+    {'type': UUID,     'ext': ext_uuid    },
+    {'type': Datetime, 'ext': ext_datetime},
 ]
 
 def default(obj):

tarantool/msgpack_ext/types/datetime.py

@@ -0,0 +1,192 @@
+from copy import deepcopy
+
+import pandas
+
+# https://www.tarantool.io/en/doc/latest/dev_guide/internals/msgpack_extensions/#the-datetime-type
+#
+# The datetime MessagePack representation looks like this:
+# +---------+----------------+==========+-----------------+
+# | MP_EXT  | MP_DATETIME    | seconds  | nsec; tzoffset; |
+# | = d7/d8 | = 4            |          | tzindex;        |
+# +---------+----------------+==========+-----------------+
+# MessagePack data contains:
+#
+# * Seconds (8 bytes) as an unencoded 64-bit signed integer stored in the
+#   little-endian order.
+# * The optional fields (8 bytes), if any of them have a non-zero value.
+#   The fields include nsec (4 bytes), tzoffset (2 bytes), and
+#   tzindex (2 bytes) packed in the little-endian order.
+#
+# seconds is seconds since Epoch, where the epoch is the point where the time
+# starts, and is platform dependent. For Unix, the epoch is January 1,
+# 1970, 00:00:00 (UTC). Tarantool uses a double type, see a structure
+# definition in src/lib/core/datetime.h and reasons in
+# https://github.com/tarantool/tarantool/wiki/Datetime-internals#intervals-in-c
+#
+# nsec is nanoseconds, fractional part of seconds. Tarantool uses int32_t, see
+# a definition in src/lib/core/datetime.h.
+#
+# tzoffset is timezone offset in minutes from UTC. Tarantool uses a int16_t type,
+# see a structure definition in src/lib/core/datetime.h.
+#
+# tzindex is Olson timezone id. Tarantool uses a int16_t type, see a structure
+# definition in src/lib/core/datetime.h. If both tzoffset and tzindex are
+# specified, tzindex has the preference and the tzoffset value is ignored.
+
+SECONDS_SIZE_BYTES  = 8
+NSEC_SIZE_BYTES     = 4
+TZOFFSET_SIZE_BYTES = 2
+TZINDEX_SIZE_BYTES  = 2
+
+BYTEORDER = 'little'
+
+NSEC_IN_SEC = 1000000000
+NSEC_IN_MKSEC = 1000
+
+def get_bytes_as_int(data, cursor, size):
+    part = data[cursor:cursor + size]
+    return int.from_bytes(part, BYTEORDER, signed=True), cursor + size
+
+def get_int_as_bytes(data, size):
+    return data.to_bytes(size, byteorder=BYTEORDER, signed=True)
+
+def msgpack_decode(data):
+    cursor = 0
+    seconds, cursor = get_bytes_as_int(data, cursor, SECONDS_SIZE_BYTES)
+
+    data_len = len(data)
+    if data_len == (SECONDS_SIZE_BYTES + NSEC_SIZE_BYTES + \
+                    TZOFFSET_SIZE_BYTES + TZINDEX_SIZE_BYTES):
+        nsec, cursor     = get_bytes_as_int(data, cursor, NSEC_SIZE_BYTES)
+        tzoffset, cursor = get_bytes_as_int(data, cursor, TZOFFSET_SIZE_BYTES)
+        tzindex, cursor  = get_bytes_as_int(data, cursor, TZINDEX_SIZE_BYTES)
+    elif data_len == SECONDS_SIZE_BYTES:
+        nsec = 0
+        tzoffset = 0
+        tzindex = 0
+    else:
+        raise MsgpackError(f'Unexpected datetime payload length {data_len}')
+
+    if (tzoffset != 0) or (tzindex != 0):
+        raise NotImplementedError
+
+    total_nsec = seconds * NSEC_IN_SEC + nsec
+
+    return pandas.to_datetime(total_nsec, unit='ns')
+
+class Datetime():
+    def __init__(self, data=None, *, timestamp=None, year=None, month=None,
+                 day=None, hour=None, minute=None, sec=None, nsec=None):
+        if data is not None:
+            if not isinstance(data, bytes):
+                raise ValueError('data argument (first positional argument) ' +
+                                 'expected to be a "bytes" instance')
+
+            self._datetime = msgpack_decode(data)
+            return
+
+        # The logic is same as in Tarantool, refer to datetime API.
+        # https://www.tarantool.io/en/doc/latest/reference/reference_lua/datetime/new/
+        if timestamp is not None:
+            if ((year is not None) or (month is not None) or \
+                    (day is not None) or (hour is not None) or \
+                    (minute is not None) or (sec is not None)):
+                raise ValueError('Cannot provide both timestamp and year, month, ' +
+                                 'day, hour, minute, sec')
+
+            if nsec is not None:
+                if not isinstance(timestamp, int):
+                    raise ValueError('timestamp must be int if nsec provided')
+
+                total_nsec = timestamp * NSEC_IN_SEC + nsec
+                self._datetime = pandas.to_datetime(total_nsec, unit='ns')
+            else:
+                self._datetime = pandas.to_datetime(timestamp, unit='s')
+        else:
+            if nsec is not None:
+                microsecond = nsec // NSEC_IN_MKSEC
+                nanosecond = nsec % NSEC_IN_MKSEC
+            else:
+                microsecond = 0
+                nanosecond = 0
+
+            self._datetime = pandas.Timestamp(year=year, month=month, day=day,
+                                              hour=hour, minute=minute, second=sec,
+                                              microsecond=microsecond,
+                                              nanosecond=nanosecond)
+
+    def __eq__(self, other):
+        if isinstance(other, Datetime):
+            return self._datetime == other._datetime
+        elif isinstance(other, pandas.Timestamp):
+            return self._datetime == other
+        else:
+            return False
+
+    def __str__(self):
+        return self._datetime.__str__()
+
+    def __repr__(self):
+        return f'datetime: {self._datetime.__repr__()}'
+
+    def __copy__(self):
+        cls = self.__class__
+        result = cls.__new__(cls)
+        result.__dict__.update(self.__dict__)
+        return result
+
+    def __deepcopy__(self, memo):
+        cls = self.__class__
+        result = cls.__new__(cls)
+        memo[id(self)] = result
+        for k, v in self.__dict__.items():
+            setattr(result, k, deepcopy(v, memo))
+        return result
+
+    @property
+    def year(self):
+        return self._datetime.year
+
+    @property
+    def month(self):
+        return self._datetime.month
+
+    @property
+    def day(self):
+        return self._datetime.day
+
+    @property
+    def hour(self):
+        return self._datetime.hour
+
+    @property
+    def minute(self):
+        return self._datetime.minute
+
+    @property
+    def sec(self):
+        return self._datetime.second
+
+    @property
+    def nsec(self):
+        # microseconds + nanoseconds
+        return self._datetime.value % NSEC_IN_SEC
+
+    @property
+    def timestamp(self):
+        return self._datetime.timestamp()
+
+    def msgpack_encode(self):
+        seconds = self._datetime.value // NSEC_IN_SEC
+        nsec = self.nsec
+        tzoffset = 0
+        tzindex = 0
+
+        buf = get_int_as_bytes(seconds, SECONDS_SIZE_BYTES)
+
+        if (nsec != 0) or (tzoffset != 0) or (tzindex != 0):
+            buf = buf + get_int_as_bytes(nsec, NSEC_SIZE_BYTES)
+            buf = buf + get_int_as_bytes(tzoffset, TZOFFSET_SIZE_BYTES)
+            buf = buf + get_int_as_bytes(tzindex, TZINDEX_SIZE_BYTES)
+
+        return buf

tarantool/msgpack_ext/unpacker.py

@@ -1,9 +1,11 @@
 import tarantool.msgpack_ext.decimal as ext_decimal
 import tarantool.msgpack_ext.uuid as ext_uuid
+import tarantool.msgpack_ext.datetime as ext_datetime
 
 decoders = {
-    ext_decimal.EXT_ID: ext_decimal.decode,
-    ext_uuid.EXT_ID   : ext_uuid.decode   ,
+    ext_decimal.EXT_ID : ext_decimal.decode ,
+    ext_uuid.EXT_ID    : ext_uuid.decode    ,
+    ext_datetime.EXT_ID: ext_datetime.decode,
 }
 
 def ext_hook(code, data):

test/suites/__init__.py

@@ -17,13 +17,14 @@
 from .test_ssl import TestSuite_Ssl
 from .test_decimal import TestSuite_Decimal
 from .test_uuid import TestSuite_UUID
+from .test_datetime import TestSuite_Datetime
 
 test_cases = (TestSuite_Schema_UnicodeConnection,
               TestSuite_Schema_BinaryConnection,
               TestSuite_Request, TestSuite_Protocol, TestSuite_Reconnect,
               TestSuite_Mesh, TestSuite_Execute, TestSuite_DBAPI,
               TestSuite_Encoding, TestSuite_Pool, TestSuite_Ssl,
-              TestSuite_Decimal, TestSuite_UUID)
+              TestSuite_Decimal, TestSuite_UUID, TestSuite_Datetime)
 
 def load_tests(loader, tests, pattern):
     suite = unittest.TestSuite()

test/suites/lib/skip.py

@@ -154,3 +154,14 @@ def skip_or_run_UUID_test(func):
 
     return skip_or_run_test_tarantool(func, '2.4.1',
                                       'does not support UUID type')
+
+def skip_or_run_datetime_test(func):
+    """Decorator to skip or run datetime-related tests depending on
+    the tarantool version.
+
+    Tarantool supports datetime type only since 2.10.0 version.
+    See https://github.com/tarantool/tarantool/issues/5941
+    """
+
+    return skip_or_run_test_pcall_require(func, 'datetime',
+                                      'does not support datetime type')