Django/docs/2.2.x/ modules/django/db/models/functions/datetime
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django.db.models.functions.datetime 源代码
from datetime import datetime
from django.conf import settings
from django.db.models.expressions import Func
from django.db.models.fields import (
DateField, DateTimeField, DurationField, Field, IntegerField, TimeField,
)
from django.db.models.lookups import (
Transform, YearExact, YearGt, YearGte, YearLt, YearLte,
)
from django.utils import timezone
class TimezoneMixin:
tzinfo = None
def get_tzname(self):
# Timezone conversions must happen to the input datetime *before*
# applying a function. 2015-12-31 23:00:00 -02:00 is stored in the
# database as 2016-01-01 01:00:00 +00:00. Any results should be
# based on the input datetime not the stored datetime.
tzname = None
if settings.USE_TZ:
if self.tzinfo is None:
tzname = timezone.get_current_timezone_name()
else:
tzname = timezone._get_timezone_name(self.tzinfo)
return tzname
[文档]class Extract(TimezoneMixin, Transform):
lookup_name = None
output_field = IntegerField()
def __init__(self, expression, lookup_name=None, tzinfo=None, **extra):
if self.lookup_name is None:
self.lookup_name = lookup_name
if self.lookup_name is None:
raise ValueError('lookup_name must be provided')
self.tzinfo = tzinfo
super().__init__(expression, **extra)
def as_sql(self, compiler, connection):
sql, params = compiler.compile(self.lhs)
lhs_output_field = self.lhs.output_field
if isinstance(lhs_output_field, DateTimeField):
tzname = self.get_tzname()
sql = connection.ops.datetime_extract_sql(self.lookup_name, sql, tzname)
elif isinstance(lhs_output_field, DateField):
sql = connection.ops.date_extract_sql(self.lookup_name, sql)
elif isinstance(lhs_output_field, TimeField):
sql = connection.ops.time_extract_sql(self.lookup_name, sql)
elif isinstance(lhs_output_field, DurationField):
if not connection.features.has_native_duration_field:
raise ValueError('Extract requires native DurationField database support.')
sql = connection.ops.time_extract_sql(self.lookup_name, sql)
else:
# resolve_expression has already validated the output_field so this
# assert should never be hit.
assert False, "Tried to Extract from an invalid type."
return sql, params
def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False):
copy = super().resolve_expression(query, allow_joins, reuse, summarize, for_save)
field = copy.lhs.output_field
if not isinstance(field, (DateField, DateTimeField, TimeField, DurationField)):
raise ValueError(
'Extract input expression must be DateField, DateTimeField, '
'TimeField, or DurationField.'
)
# Passing dates to functions expecting datetimes is most likely a mistake.
if type(field) == DateField and copy.lookup_name in ('hour', 'minute', 'second'):
raise ValueError(
"Cannot extract time component '%s' from DateField '%s'. " % (copy.lookup_name, field.name)
)
return copy
[文档]class ExtractYear(Extract):
lookup_name = 'year'
[文档]class ExtractIsoYear(Extract):
"""Return the ISO-8601 week-numbering year."""
lookup_name = 'iso_year'
[文档]class ExtractMonth(Extract):
lookup_name = 'month'
[文档]class ExtractDay(Extract):
lookup_name = 'day'
[文档]class ExtractWeek(Extract):
"""
Return 1-52 or 53, based on ISO-8601, i.e., Monday is the first of the
week.
"""
lookup_name = 'week'
[文档]class ExtractWeekDay(Extract):
"""
Return Sunday=1 through Saturday=7.
To replicate this in Python: (mydatetime.isoweekday() % 7) + 1
"""
lookup_name = 'week_day'
[文档]class ExtractQuarter(Extract):
lookup_name = 'quarter'
[文档]class ExtractHour(Extract):
lookup_name = 'hour'
[文档]class ExtractMinute(Extract):
lookup_name = 'minute'
[文档]class ExtractSecond(Extract):
lookup_name = 'second'
DateField.register_lookup(ExtractYear)
DateField.register_lookup(ExtractMonth)
DateField.register_lookup(ExtractDay)
DateField.register_lookup(ExtractWeekDay)
DateField.register_lookup(ExtractWeek)
DateField.register_lookup(ExtractIsoYear)
DateField.register_lookup(ExtractQuarter)
TimeField.register_lookup(ExtractHour)
TimeField.register_lookup(ExtractMinute)
TimeField.register_lookup(ExtractSecond)
DateTimeField.register_lookup(ExtractHour)
DateTimeField.register_lookup(ExtractMinute)
DateTimeField.register_lookup(ExtractSecond)
ExtractYear.register_lookup(YearExact)
ExtractYear.register_lookup(YearGt)
ExtractYear.register_lookup(YearGte)
ExtractYear.register_lookup(YearLt)
ExtractYear.register_lookup(YearLte)
ExtractIsoYear.register_lookup(YearExact)
ExtractIsoYear.register_lookup(YearGt)
ExtractIsoYear.register_lookup(YearGte)
ExtractIsoYear.register_lookup(YearLt)
ExtractIsoYear.register_lookup(YearLte)
[文档]class Now(Func):
template = 'CURRENT_TIMESTAMP'
output_field = DateTimeField()
def as_postgresql(self, compiler, connection, **extra_context):
# PostgreSQL's CURRENT_TIMESTAMP means "the time at the start of the
# transaction". Use STATEMENT_TIMESTAMP to be cross-compatible with
# other databases.
return self.as_sql(compiler, connection, template='STATEMENT_TIMESTAMP()', **extra_context)
class TruncBase(TimezoneMixin, Transform):
kind = None
tzinfo = None
def __init__(self, expression, output_field=None, tzinfo=None, **extra):
self.tzinfo = tzinfo
super().__init__(expression, output_field=output_field, **extra)
def as_sql(self, compiler, connection):
inner_sql, inner_params = compiler.compile(self.lhs)
if isinstance(self.output_field, DateTimeField):
tzname = self.get_tzname()
sql = connection.ops.datetime_trunc_sql(self.kind, inner_sql, tzname)
elif isinstance(self.output_field, DateField):
sql = connection.ops.date_trunc_sql(self.kind, inner_sql)
elif isinstance(self.output_field, TimeField):
sql = connection.ops.time_trunc_sql(self.kind, inner_sql)
else:
raise ValueError('Trunc only valid on DateField, TimeField, or DateTimeField.')
return sql, inner_params
def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False):
copy = super().resolve_expression(query, allow_joins, reuse, summarize, for_save)
field = copy.lhs.output_field
# DateTimeField is a subclass of DateField so this works for both.
assert isinstance(field, (DateField, TimeField)), (
"%r isn't a DateField, TimeField, or DateTimeField." % field.name
)
# If self.output_field was None, then accessing the field will trigger
# the resolver to assign it to self.lhs.output_field.
if not isinstance(copy.output_field, (DateField, DateTimeField, TimeField)):
raise ValueError('output_field must be either DateField, TimeField, or DateTimeField')
# Passing dates or times to functions expecting datetimes is most
# likely a mistake.
class_output_field = self.__class__.output_field if isinstance(self.__class__.output_field, Field) else None
output_field = class_output_field or copy.output_field
has_explicit_output_field = class_output_field or field.__class__ is not copy.output_field.__class__
if type(field) == DateField and (
isinstance(output_field, DateTimeField) or copy.kind in ('hour', 'minute', 'second', 'time')):
raise ValueError("Cannot truncate DateField '%s' to %s. " % (
field.name, output_field.__class__.__name__ if has_explicit_output_field else 'DateTimeField'
))
elif isinstance(field, TimeField) and (
isinstance(output_field, DateTimeField) or
copy.kind in ('year', 'quarter', 'month', 'week', 'day', 'date')):
raise ValueError("Cannot truncate TimeField '%s' to %s. " % (
field.name, output_field.__class__.__name__ if has_explicit_output_field else 'DateTimeField'
))
return copy
def convert_value(self, value, expression, connection):
if isinstance(self.output_field, DateTimeField):
if not settings.USE_TZ:
pass
elif value is not None:
value = value.replace(tzinfo=None)
value = timezone.make_aware(value, self.tzinfo)
elif not connection.features.has_zoneinfo_database:
raise ValueError(
'Database returned an invalid datetime value. Are time '
'zone definitions for your database installed?'
)
elif isinstance(value, datetime):
if value is None:
pass
elif isinstance(self.output_field, DateField):
value = value.date()
elif isinstance(self.output_field, TimeField):
value = value.time()
return value
[文档]class Trunc(TruncBase):
def __init__(self, expression, kind, output_field=None, tzinfo=None, **extra):
self.kind = kind
super().__init__(expression, output_field=output_field, tzinfo=tzinfo, **extra)
[文档]class TruncYear(TruncBase):
kind = 'year'
[文档]class TruncQuarter(TruncBase):
kind = 'quarter'
[文档]class TruncMonth(TruncBase):
kind = 'month'
[文档]class TruncWeek(TruncBase):
"""Truncate to midnight on the Monday of the week."""
kind = 'week'
[文档]class TruncDay(TruncBase):
kind = 'day'
[文档]class TruncDate(TruncBase):
kind = 'date'
lookup_name = 'date'
output_field = DateField()
def as_sql(self, compiler, connection):
# Cast to date rather than truncate to date.
lhs, lhs_params = compiler.compile(self.lhs)
tzname = timezone.get_current_timezone_name() if settings.USE_TZ else None
sql = connection.ops.datetime_cast_date_sql(lhs, tzname)
return sql, lhs_params
[文档]class TruncTime(TruncBase):
kind = 'time'
lookup_name = 'time'
output_field = TimeField()
def as_sql(self, compiler, connection):
# Cast to time rather than truncate to time.
lhs, lhs_params = compiler.compile(self.lhs)
tzname = timezone.get_current_timezone_name() if settings.USE_TZ else None
sql = connection.ops.datetime_cast_time_sql(lhs, tzname)
return sql, lhs_params
[文档]class TruncHour(TruncBase):
kind = 'hour'
[文档]class TruncMinute(TruncBase):
kind = 'minute'
[文档]class TruncSecond(TruncBase):
kind = 'second'
DateTimeField.register_lookup(TruncDate)
DateTimeField.register_lookup(TruncTime)
