Source code for django.db.models.expressions

import copy
import datetime

from django.conf import settings
from django.core.exceptions import FieldError
from django.db.backends import utils as backend_utils
from django.db.models import fields
from django.db.models.constants import LOOKUP_SEP
from django.db.models.query_utils import Q, refs_aggregate
from django.utils import six, timezone
from django.utils.functional import cached_property


class Combinable(object):
    """
    Provides the ability to combine one or two objects with
    some connector. For example F('foo') + F('bar').
    """

    # Arithmetic connectors
    ADD = '+'
    SUB = '-'
    MUL = '*'
    DIV = '/'
    POW = '^'
    # The following is a quoted % operator - it is quoted because it can be
    # used in strings that also have parameter substitution.
    MOD = '%%'

    # Bitwise operators - note that these are generated by .bitand()
    # and .bitor(), the '&' and '|' are reserved for boolean operator
    # usage.
    BITAND = '&'
    BITOR = '|'

    def _combine(self, other, connector, reversed, node=None):
        if not hasattr(other, 'resolve_expression'):
            # everything must be resolvable to an expression
            if isinstance(other, datetime.timedelta):
                other = DurationValue(other, output_field=fields.DurationField())
            else:
                other = Value(other)

        if reversed:
            return CombinedExpression(other, connector, self)
        return CombinedExpression(self, connector, other)

    #############
    # OPERATORS #
    #############

    def __add__(self, other):
        return self._combine(other, self.ADD, False)

    def __sub__(self, other):
        return self._combine(other, self.SUB, False)

    def __mul__(self, other):
        return self._combine(other, self.MUL, False)

    def __truediv__(self, other):
        return self._combine(other, self.DIV, False)

    def __div__(self, other):  # Python 2 compatibility
        return type(self).__truediv__(self, other)

    def __mod__(self, other):
        return self._combine(other, self.MOD, False)

    def __pow__(self, other):
        return self._combine(other, self.POW, False)

    def __and__(self, other):
        raise NotImplementedError(
            "Use .bitand() and .bitor() for bitwise logical operations."
        )

    def bitand(self, other):
        return self._combine(other, self.BITAND, False)

    def __or__(self, other):
        raise NotImplementedError(
            "Use .bitand() and .bitor() for bitwise logical operations."
        )

    def bitor(self, other):
        return self._combine(other, self.BITOR, False)

    def __radd__(self, other):
        return self._combine(other, self.ADD, True)

    def __rsub__(self, other):
        return self._combine(other, self.SUB, True)

    def __rmul__(self, other):
        return self._combine(other, self.MUL, True)

    def __rtruediv__(self, other):
        return self._combine(other, self.DIV, True)

    def __rdiv__(self, other):  # Python 2 compatibility
        return type(self).__rtruediv__(self, other)

    def __rmod__(self, other):
        return self._combine(other, self.MOD, True)

    def __rpow__(self, other):
        return self._combine(other, self.POW, True)

    def __rand__(self, other):
        raise NotImplementedError(
            "Use .bitand() and .bitor() for bitwise logical operations."
        )

    def __ror__(self, other):
        raise NotImplementedError(
            "Use .bitand() and .bitor() for bitwise logical operations."
        )


class BaseExpression(object):
    """
    Base class for all query expressions.
    """

    # aggregate specific fields
    is_summary = False

    def __init__(self, output_field=None):
        self._output_field = output_field

    def get_db_converters(self, connection):
        return [self.convert_value] + self.output_field.get_db_converters(connection)

    def get_source_expressions(self):
        return []

    def set_source_expressions(self, exprs):
        assert len(exprs) == 0

    def _parse_expressions(self, *expressions):
        return [
            arg if hasattr(arg, 'resolve_expression') else (
                F(arg) if isinstance(arg, six.string_types) else Value(arg)
            ) for arg in expressions
        ]

    def as_sql(self, compiler, connection):
        """
        Responsible for returning a (sql, [params]) tuple to be included
        in the current query.

        Different backends can provide their own implementation, by
        providing an `as_{vendor}` method and patching the Expression:

        ```
        def override_as_sql(self, compiler, connection):
            # custom logic
            return super(Expression, self).as_sql(compiler, connection)
        setattr(Expression, 'as_' + connection.vendor, override_as_sql)
        ```

        Arguments:
         * compiler: the query compiler responsible for generating the query.
           Must have a compile method, returning a (sql, [params]) tuple.
           Calling compiler(value) will return a quoted `value`.

         * connection: the database connection used for the current query.

        Returns: (sql, params)
          Where `sql` is a string containing ordered sql parameters to be
          replaced with the elements of the list `params`.
        """
        raise NotImplementedError("Subclasses must implement as_sql()")

    @cached_property
    def contains_aggregate(self):
        for expr in self.get_source_expressions():
            if expr and expr.contains_aggregate:
                return True
        return False

    @cached_property
    def contains_column_references(self):
        for expr in self.get_source_expressions():
            if expr and expr.contains_column_references:
                return True
        return False

    def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False):
        """
        Provides the chance to do any preprocessing or validation before being
        added to the query.

        Arguments:
         * query: the backend query implementation
         * allow_joins: boolean allowing or denying use of joins
           in this query
         * reuse: a set of reusable joins for multijoins
         * summarize: a terminal aggregate clause
         * for_save: whether this expression about to be used in a save or update

        Returns: an Expression to be added to the query.
        """
        c = self.copy()
        c.is_summary = summarize
        c.set_source_expressions([
            expr.resolve_expression(query, allow_joins, reuse, summarize)
            for expr in c.get_source_expressions()
        ])
        return c

    def _prepare(self, field):
        """
        Hook used by Field.get_prep_lookup() to do custom preparation.
        """
        return self

    @property
    def field(self):
        return self.output_field

    @cached_property
    def output_field(self):
        """
        Returns the output type of this expressions.
        """
        if self._output_field_or_none is None:
            raise FieldError("Cannot resolve expression type, unknown output_field")
        return self._output_field_or_none

    @cached_property
    def _output_field_or_none(self):
        """
        Returns the output field of this expression, or None if no output type
        can be resolved. Note that the 'output_field' property will raise
        FieldError if no type can be resolved, but this attribute allows for
        None values.
        """
        if self._output_field is None:
            self._resolve_output_field()
        return self._output_field

    def _resolve_output_field(self):
        """
        Attempts to infer the output type of the expression. If the output
        fields of all source fields match then we can simply infer the same
        type here. This isn't always correct, but it makes sense most of the
        time.

        Consider the difference between `2 + 2` and `2 / 3`. Inferring
        the type here is a convenience for the common case. The user should
        supply their own output_field with more complex computations.

        If a source does not have an `_output_field` then we exclude it from
        this check. If all sources are `None`, then an error will be thrown
        higher up the stack in the `output_field` property.
        """
        if self._output_field is None:
            sources = self.get_source_fields()
            num_sources = len(sources)
            if num_sources == 0:
                self._output_field = None
            else:
                for source in sources:
                    if self._output_field is None:
                        self._output_field = source
                    if source is not None and not isinstance(self._output_field, source.__class__):
                        raise FieldError(
                            "Expression contains mixed types. You must set output_field")

    def convert_value(self, value, expression, connection, context):
        """
        Expressions provide their own converters because users have the option
        of manually specifying the output_field which may be a different type
        from the one the database returns.
        """
        field = self.output_field
        internal_type = field.get_internal_type()
        if value is None:
            return value
        elif internal_type == 'FloatField':
            return float(value)
        elif internal_type.endswith('IntegerField'):
            return int(value)
        elif internal_type == 'DecimalField':
            return backend_utils.typecast_decimal(value)
        return value

    def get_lookup(self, lookup):
        return self.output_field.get_lookup(lookup)

    def get_transform(self, name):
        return self.output_field.get_transform(name)

    def relabeled_clone(self, change_map):
        clone = self.copy()
        clone.set_source_expressions(
            [e.relabeled_clone(change_map) for e in self.get_source_expressions()])
        return clone

    def copy(self):
        c = copy.copy(self)
        c.copied = True
        return c

    def refs_aggregate(self, existing_aggregates):
        """
        Does this expression contain a reference to some of the
        existing aggregates? If so, returns the aggregate and also
        the lookup parts that *weren't* found. So, if
            existing_aggregates = {'max_id': Max('id')}
            self.name = 'max_id'
            queryset.filter(max_id__range=[10,100])
        then this method will return Max('id') and those parts of the
        name that weren't found. In this case `max_id` is found and the range
        portion is returned as ('range',).
        """
        for node in self.get_source_expressions():
            agg, lookup = node.refs_aggregate(existing_aggregates)
            if agg:
                return agg, lookup
        return False, ()

    def get_group_by_cols(self):
        if not self.contains_aggregate:
            return [self]
        cols = []
        for source in self.get_source_expressions():
            cols.extend(source.get_group_by_cols())
        return cols

    def get_source_fields(self):
        """
        Returns the underlying field types used by this
        aggregate.
        """
        return [e._output_field_or_none for e in self.get_source_expressions()]

    def asc(self):
        return OrderBy(self)

    def desc(self):
        return OrderBy(self, descending=True)

    def reverse_ordering(self):
        return self

    def flatten(self):
        """
        Recursively yield this expression and all subexpressions, in
        depth-first order.
        """
        yield self
        for expr in self.get_source_expressions():
            if expr:
                for inner_expr in expr.flatten():
                    yield inner_expr


[docs]class Expression(BaseExpression, Combinable): """ An expression that can be combined with other expressions. """ pass
class CombinedExpression(Expression): def __init__(self, lhs, connector, rhs, output_field=None): super(CombinedExpression, self).__init__(output_field=output_field) self.connector = connector self.lhs = lhs self.rhs = rhs def __repr__(self): return "<{}: {}>".format(self.__class__.__name__, self) def __str__(self): return "{} {} {}".format(self.lhs, self.connector, self.rhs) def get_source_expressions(self): return [self.lhs, self.rhs] def set_source_expressions(self, exprs): self.lhs, self.rhs = exprs def as_sql(self, compiler, connection): try: lhs_output = self.lhs.output_field except FieldError: lhs_output = None try: rhs_output = self.rhs.output_field except FieldError: rhs_output = None if (not connection.features.has_native_duration_field and ((lhs_output and lhs_output.get_internal_type() == 'DurationField') or (rhs_output and rhs_output.get_internal_type() == 'DurationField'))): return DurationExpression(self.lhs, self.connector, self.rhs).as_sql(compiler, connection) expressions = [] expression_params = [] sql, params = compiler.compile(self.lhs) expressions.append(sql) expression_params.extend(params) sql, params = compiler.compile(self.rhs) expressions.append(sql) expression_params.extend(params) # order of precedence expression_wrapper = '(%s)' sql = connection.ops.combine_expression(self.connector, expressions) return expression_wrapper % sql, expression_params def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): c = self.copy() c.is_summary = summarize c.lhs = c.lhs.resolve_expression(query, allow_joins, reuse, summarize, for_save) c.rhs = c.rhs.resolve_expression(query, allow_joins, reuse, summarize, for_save) return c class DurationExpression(CombinedExpression): def compile(self, side, compiler, connection): if not isinstance(side, DurationValue): try: output = side.output_field except FieldError: pass else: if output.get_internal_type() == 'DurationField': sql, params = compiler.compile(side) return connection.ops.format_for_duration_arithmetic(sql), params return compiler.compile(side) def as_sql(self, compiler, connection): connection.ops.check_expression_support(self) expressions = [] expression_params = [] sql, params = self.compile(self.lhs, compiler, connection) expressions.append(sql) expression_params.extend(params) sql, params = self.compile(self.rhs, compiler, connection) expressions.append(sql) expression_params.extend(params) # order of precedence expression_wrapper = '(%s)' sql = connection.ops.combine_duration_expression(self.connector, expressions) return expression_wrapper % sql, expression_params
[docs]class F(Combinable): """ An object capable of resolving references to existing query objects. """ def __init__(self, name): """ Arguments: * name: the name of the field this expression references """ self.name = name def __repr__(self): return "{}({})".format(self.__class__.__name__, self.name) def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): return query.resolve_ref(self.name, allow_joins, reuse, summarize) def refs_aggregate(self, existing_aggregates): return refs_aggregate(self.name.split(LOOKUP_SEP), existing_aggregates) def asc(self): return OrderBy(self) def desc(self): return OrderBy(self, descending=True)
[docs]class Func(Expression): """ An SQL function call. """ function = None template = '%(function)s(%(expressions)s)' arg_joiner = ', ' def __init__(self, *expressions, **extra): output_field = extra.pop('output_field', None) super(Func, self).__init__(output_field=output_field) self.source_expressions = self._parse_expressions(*expressions) self.extra = extra def __repr__(self): args = self.arg_joiner.join(str(arg) for arg in self.source_expressions) extra = ', '.join(str(key) + '=' + str(val) for key, val in self.extra.items()) if extra: return "{}({}, {})".format(self.__class__.__name__, args, extra) return "{}({})".format(self.__class__.__name__, args) def get_source_expressions(self): return self.source_expressions def set_source_expressions(self, exprs): self.source_expressions = exprs def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): c = self.copy() c.is_summary = summarize for pos, arg in enumerate(c.source_expressions): c.source_expressions[pos] = arg.resolve_expression(query, allow_joins, reuse, summarize, for_save) return c def as_sql(self, compiler, connection, function=None, template=None): connection.ops.check_expression_support(self) sql_parts = [] params = [] for arg in self.source_expressions: arg_sql, arg_params = compiler.compile(arg) sql_parts.append(arg_sql) params.extend(arg_params) if function is None: self.extra['function'] = self.extra.get('function', self.function) else: self.extra['function'] = function self.extra['expressions'] = self.extra['field'] = self.arg_joiner.join(sql_parts) template = template or self.extra.get('template', self.template) return template % self.extra, params def as_sqlite(self, *args, **kwargs): sql, params = self.as_sql(*args, **kwargs) try: if self.output_field.get_internal_type() == 'DecimalField': sql = 'CAST(%s AS NUMERIC)' % sql except FieldError: pass return sql, params def copy(self): copy = super(Func, self).copy() copy.source_expressions = self.source_expressions[:] copy.extra = self.extra.copy() return copy
[docs]class Value(Expression): """ Represents a wrapped value as a node within an expression """ def __init__(self, value, output_field=None): """ Arguments: * value: the value this expression represents. The value will be added into the sql parameter list and properly quoted. * output_field: an instance of the model field type that this expression will return, such as IntegerField() or CharField(). """ super(Value, self).__init__(output_field=output_field) self.value = value def __repr__(self): return "{}({})".format(self.__class__.__name__, self.value) def as_sql(self, compiler, connection): connection.ops.check_expression_support(self) val = self.value # check _output_field to avoid triggering an exception if self._output_field is not None: if self.for_save: val = self.output_field.get_db_prep_save(val, connection=connection) else: val = self.output_field.get_db_prep_value(val, connection=connection) if val is None: # cx_Oracle does not always convert None to the appropriate # NULL type (like in case expressions using numbers), so we # use a literal SQL NULL return 'NULL', [] return '%s', [val] def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): c = super(Value, self).resolve_expression(query, allow_joins, reuse, summarize, for_save) c.for_save = for_save return c def get_group_by_cols(self): return []
class DurationValue(Value): def as_sql(self, compiler, connection): connection.ops.check_expression_support(self) if (connection.features.has_native_duration_field and connection.features.driver_supports_timedelta_args): return super(DurationValue, self).as_sql(compiler, connection) return connection.ops.date_interval_sql(self.value)
[docs]class RawSQL(Expression): def __init__(self, sql, params, output_field=None): if output_field is None: output_field = fields.Field() self.sql, self.params = sql, params super(RawSQL, self).__init__(output_field=output_field) def __repr__(self): return "{}({}, {})".format(self.__class__.__name__, self.sql, self.params) def as_sql(self, compiler, connection): return '(%s)' % self.sql, self.params def get_group_by_cols(self): return [self]
class Star(Expression): def __repr__(self): return "'*'" def as_sql(self, compiler, connection): return '*', [] class Random(Expression): def __init__(self): super(Random, self).__init__(output_field=fields.FloatField()) def __repr__(self): return "Random()" def as_sql(self, compiler, connection): return connection.ops.random_function_sql(), [] class Col(Expression): contains_column_references = True def __init__(self, alias, target, output_field=None): if output_field is None: output_field = target super(Col, self).__init__(output_field=output_field) self.alias, self.target = alias, target def __repr__(self): return "{}({}, {})".format( self.__class__.__name__, self.alias, self.target) def as_sql(self, compiler, connection): qn = compiler.quote_name_unless_alias return "%s.%s" % (qn(self.alias), qn(self.target.column)), [] def relabeled_clone(self, relabels): return self.__class__(relabels.get(self.alias, self.alias), self.target, self.output_field) def get_group_by_cols(self): return [self] def get_db_converters(self, connection): if self.target == self.output_field: return self.output_field.get_db_converters(connection) return (self.output_field.get_db_converters(connection) + self.target.get_db_converters(connection)) class Ref(Expression): """ Reference to column alias of the query. For example, Ref('sum_cost') in qs.annotate(sum_cost=Sum('cost')) query. """ def __init__(self, refs, source): super(Ref, self).__init__() self.refs, self.source = refs, source def __repr__(self): return "{}({}, {})".format(self.__class__.__name__, self.refs, self.source) def get_source_expressions(self): return [self.source] def set_source_expressions(self, exprs): self.source, = exprs def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): # The sub-expression `source` has already been resolved, as this is # just a reference to the name of `source`. return self def relabeled_clone(self, relabels): return self def as_sql(self, compiler, connection): return "%s" % connection.ops.quote_name(self.refs), [] def get_group_by_cols(self): return [self]
[docs]class ExpressionWrapper(Expression): """ An expression that can wrap another expression so that it can provide extra context to the inner expression, such as the output_field. """ def __init__(self, expression, output_field): super(ExpressionWrapper, self).__init__(output_field=output_field) self.expression = expression def set_source_expressions(self, exprs): self.expression = exprs[0] def get_source_expressions(self): return [self.expression] def as_sql(self, compiler, connection): return self.expression.as_sql(compiler, connection) def __repr__(self): return "{}({})".format(self.__class__.__name__, self.expression)
[docs]class When(Expression): template = 'WHEN %(condition)s THEN %(result)s' def __init__(self, condition=None, then=None, **lookups): if lookups and condition is None: condition, lookups = Q(**lookups), None if condition is None or not isinstance(condition, Q) or lookups: raise TypeError("__init__() takes either a Q object or lookups as keyword arguments") super(When, self).__init__(output_field=None) self.condition = condition self.result = self._parse_expressions(then)[0] def __str__(self): return "WHEN %r THEN %r" % (self.condition, self.result) def __repr__(self): return "<%s: %s>" % (self.__class__.__name__, self) def get_source_expressions(self): return [self.condition, self.result] def set_source_expressions(self, exprs): self.condition, self.result = exprs def get_source_fields(self): # We're only interested in the fields of the result expressions. return [self.result._output_field_or_none] def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): c = self.copy() c.is_summary = summarize if hasattr(c.condition, 'resolve_expression'): c.condition = c.condition.resolve_expression(query, allow_joins, reuse, summarize, False) c.result = c.result.resolve_expression(query, allow_joins, reuse, summarize, for_save) return c def as_sql(self, compiler, connection, template=None): connection.ops.check_expression_support(self) template_params = {} sql_params = [] condition_sql, condition_params = compiler.compile(self.condition) template_params['condition'] = condition_sql sql_params.extend(condition_params) result_sql, result_params = compiler.compile(self.result) template_params['result'] = result_sql sql_params.extend(result_params) template = template or self.template return template % template_params, sql_params def get_group_by_cols(self): # This is not a complete expression and cannot be used in GROUP BY. cols = [] for source in self.get_source_expressions(): cols.extend(source.get_group_by_cols()) return cols
[docs]class Case(Expression): """ An SQL searched CASE expression: CASE WHEN n > 0 THEN 'positive' WHEN n < 0 THEN 'negative' ELSE 'zero' END """ template = 'CASE %(cases)s ELSE %(default)s END' case_joiner = ' ' def __init__(self, *cases, **extra): if not all(isinstance(case, When) for case in cases): raise TypeError("Positional arguments must all be When objects.") default = extra.pop('default', None) output_field = extra.pop('output_field', None) super(Case, self).__init__(output_field) self.cases = list(cases) self.default = self._parse_expressions(default)[0] def __str__(self): return "CASE %s, ELSE %r" % (', '.join(str(c) for c in self.cases), self.default) def __repr__(self): return "<%s: %s>" % (self.__class__.__name__, self) def get_source_expressions(self): return self.cases + [self.default] def set_source_expressions(self, exprs): self.cases = exprs[:-1] self.default = exprs[-1] def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): c = self.copy() c.is_summary = summarize for pos, case in enumerate(c.cases): c.cases[pos] = case.resolve_expression(query, allow_joins, reuse, summarize, for_save) c.default = c.default.resolve_expression(query, allow_joins, reuse, summarize, for_save) return c def copy(self): c = super(Case, self).copy() c.cases = c.cases[:] return c def as_sql(self, compiler, connection, template=None, extra=None): connection.ops.check_expression_support(self) if not self.cases: return compiler.compile(self.default) template_params = dict(extra) if extra else {} case_parts = [] sql_params = [] for case in self.cases: case_sql, case_params = compiler.compile(case) case_parts.append(case_sql) sql_params.extend(case_params) template_params['cases'] = self.case_joiner.join(case_parts) default_sql, default_params = compiler.compile(self.default) template_params['default'] = default_sql sql_params.extend(default_params) template = template or self.template sql = template % template_params if self._output_field_or_none is not None: sql = connection.ops.unification_cast_sql(self.output_field) % sql return sql, sql_params
class Date(Expression): """ Add a date selection column. """ def __init__(self, lookup, lookup_type): super(Date, self).__init__(output_field=fields.DateField()) self.lookup = lookup self.col = None self.lookup_type = lookup_type def __repr__(self): return "{}({}, {})".format(self.__class__.__name__, self.lookup, self.lookup_type) def get_source_expressions(self): return [self.col] def set_source_expressions(self, exprs): self.col, = exprs def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): copy = self.copy() copy.col = query.resolve_ref(self.lookup, allow_joins, reuse, summarize) field = copy.col.output_field assert isinstance(field, fields.DateField), "%r isn't a DateField." % field.name if settings.USE_TZ: assert not isinstance(field, fields.DateTimeField), ( "%r is a DateTimeField, not a DateField." % field.name ) return copy def as_sql(self, compiler, connection): sql, params = self.col.as_sql(compiler, connection) assert not(params) return connection.ops.date_trunc_sql(self.lookup_type, sql), [] def copy(self): copy = super(Date, self).copy() copy.lookup = self.lookup copy.lookup_type = self.lookup_type return copy def convert_value(self, value, expression, connection, context): if isinstance(value, datetime.datetime): value = value.date() return value class DateTime(Expression): """ Add a datetime selection column. """ def __init__(self, lookup, lookup_type, tzinfo): super(DateTime, self).__init__(output_field=fields.DateTimeField()) self.lookup = lookup self.col = None self.lookup_type = lookup_type if tzinfo is None: self.tzname = None else: self.tzname = timezone._get_timezone_name(tzinfo) self.tzinfo = tzinfo def __repr__(self): return "{}({}, {}, {})".format( self.__class__.__name__, self.lookup, self.lookup_type, self.tzinfo) def get_source_expressions(self): return [self.col] def set_source_expressions(self, exprs): self.col, = exprs def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): copy = self.copy() copy.col = query.resolve_ref(self.lookup, allow_joins, reuse, summarize) field = copy.col.output_field assert isinstance(field, fields.DateTimeField), ( "%r isn't a DateTimeField." % field.name ) return copy def as_sql(self, compiler, connection): sql, params = self.col.as_sql(compiler, connection) assert not(params) return connection.ops.datetime_trunc_sql(self.lookup_type, sql, self.tzname) def copy(self): copy = super(DateTime, self).copy() copy.lookup = self.lookup copy.lookup_type = self.lookup_type copy.tzname = self.tzname return copy def convert_value(self, value, expression, connection, context): if settings.USE_TZ: if value is None: raise ValueError( "Database returned an invalid value in QuerySet.datetimes(). " "Are time zone definitions for your database and pytz installed?" ) value = value.replace(tzinfo=None) value = timezone.make_aware(value, self.tzinfo) return value class OrderBy(BaseExpression): template = '%(expression)s %(ordering)s' def __init__(self, expression, descending=False): self.descending = descending if not hasattr(expression, 'resolve_expression'): raise ValueError('expression must be an expression type') self.expression = expression def __repr__(self): return "{}({}, descending={})".format( self.__class__.__name__, self.expression, self.descending) def set_source_expressions(self, exprs): self.expression = exprs[0] def get_source_expressions(self): return [self.expression] def as_sql(self, compiler, connection): connection.ops.check_expression_support(self) expression_sql, params = compiler.compile(self.expression) placeholders = {'expression': expression_sql} placeholders['ordering'] = 'DESC' if self.descending else 'ASC' return (self.template % placeholders).rstrip(), params def get_group_by_cols(self): cols = [] for source in self.get_source_expressions(): cols.extend(source.get_group_by_cols()) return cols def reverse_ordering(self): self.descending = not self.descending return self def asc(self): self.descending = False def desc(self): self.descending = True
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