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` objects may be encoded to Tarantool datetime
objects.

`tarantool.Datetime` is basically a `pandas.Timestamp` wrapper. You can
create `tarantool.Datetime` objects
- from `pandas.Timestamp` object,
- by using the same API as in `pandas.Timestamp()` [2],
- from another `tarantool.Datetime` object.

To work with datetime data as a `pandas.Timestamp`, convert
`tarantool.Datetime` object to a `pandas.Timestamp` with
`to_pd_timestamp()` method call. You can use this `pandas.Timestamp`
object to build a `tarantool.Datetime` object before sending data to
Tarantool.

To work with data as `numpy.datetime64` or `datetime.datetime`, convert
to a `pandas.Timestamp` and then use `to_datetime64()` or
`to_datetime()` converter.

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 reason we use custom class
instead of plain pandas.Timestamp.

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

Author: DifferentialOrange

CHANGELOG.md

@@ -9,6 +9,27 @@ 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.
+
+  `tarantool.Datetime` is basically a `pandas.Timestamp` wrapper.
+  You can create `tarantool.Datetime` objects
+  - from `pandas.Timestamp` object,
+  - by using the same API as in `pandas.Timestamp()`,
+  - from another `tarantool.Datetime` object.
+
+  To work with datetime data as a `pandas.Timestamp`, convert
+  `tarantool.Datetime` object to a `pandas.Timestamp` with
+  `to_pd_timestamp()` method call. You can use this
+  `pandas.Timestamp` object to build a `tarantool.Datetime`
+  object before sending data to Tarantool.
+
+  To work with data as `numpy.datetime64` or `datetime.datetime`,
+  convert to a `pandas.Timestamp` and then use `to_datetime64()`
+  or `to_datetime()` converter.
 
 ### 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 +1,126 @@
+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
+
+
+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)
+
+    if len(data) > SECONDS_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 len(data) == SECONDS_SIZE_BYTES:
+        nsec = 0
+        tzoffset = 0
+        tzindex = 0
+    else:
+        raise MsgpackError('Unexpected datetime payload length')
+
+    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, *args, **kwargs):
+        if len(args) > 0:
+            data = args[0]
+            if isinstance(data, bytes):
+                self._timestamp = msgpack_decode(data)
+                return
+
+            if isinstance(data, pandas.Timestamp):
+                self._timestamp = = deepcopy(data)
+                return
+
+            if isinstance(data, Datetime):
+                self._timestamp = deepcopy(data._timestamp)
+                return
+        else:
+            self._timestamp = pandas.Timestamp(*args, **kwargs)
+            return
+
+    def __eq__(self, other):
+        if isinstance(other, Datetime):
+            return self._timestamp == other._timestamp
+        elif isinstance(other, pandas.Timestamp):
+            return self._timestamp == other
+        else:
+            return False
+
+    def __str__(self):
+        return self._timestamp.__str__()
+
+    def __repr__(self):
+        return self._timestamp.__repr__()
+
+    def to_pd_timestamp(self):
+        return deepcopy(self._timestamp)
+
+    def msgpack_encode(self):
+        ts_value = self._timestamp.value
+
+        seconds = ts_value // NSEC_IN_SEC
+        nsec = ts_value % NSEC_IN_SEC
+        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')