django/db/models/expressions.py
import copy
import datetime
import functools
import inspect
from collections import defaultdict
from decimal import Decimal
from enum import Enum
from itertools import chain
from types import NoneType
from uuid import UUID
from django.core.exceptions import EmptyResultSet, FieldError, FullResultSet
from django.db import DatabaseError, NotSupportedError, connection
from django.db.models import fields
from django.db.models.constants import LOOKUP_SEP
from django.db.models.query_utils import Q
from django.utils.deconstruct import deconstructible
from django.utils.functional import cached_property, classproperty
from django.utils.hashable import make_hashable
class SQLiteNumericMixin:
"""
Some expressions with output_field=DecimalField() must be cast to
numeric to be properly filtered.
"""
def as_sqlite(self, compiler, connection, **extra_context):
sql, params = self.as_sql(compiler, connection, **extra_context)
try:
if self.output_field.get_internal_type() == "DecimalField":
sql = "(CAST(%s AS NUMERIC))" % sql
except FieldError:
pass
return sql, params
class Combinable:
"""
Provide 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 = "|"
BITLEFTSHIFT = "<<"
BITRIGHTSHIFT = ">>"
BITXOR = "#"
def _combine(self, other, connector, reversed):
if not hasattr(other, "resolve_expression"):
# everything must be resolvable to an expression
other = Value(other)
if reversed:
return CombinedExpression(other, connector, self)
return CombinedExpression(self, connector, other)
#############
# OPERATORS #
#############
def __neg__(self):
return self._combine(-1, self.MUL, False)
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 __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):
if getattr(self, "conditional", False) and getattr(other, "conditional", False):
return Q(self) & Q(other)
raise NotImplementedError(
"Use .bitand(), .bitor(), and .bitxor() for bitwise logical operations."
)
def bitand(self, other):
return self._combine(other, self.BITAND, False)
def bitleftshift(self, other):
return self._combine(other, self.BITLEFTSHIFT, False)
def bitrightshift(self, other):
return self._combine(other, self.BITRIGHTSHIFT, False)
def __xor__(self, other):
if getattr(self, "conditional", False) and getattr(other, "conditional", False):
return Q(self) ^ Q(other)
raise NotImplementedError(
"Use .bitand(), .bitor(), and .bitxor() for bitwise logical operations."
)
def bitxor(self, other):
return self._combine(other, self.BITXOR, False)
def __or__(self, other):
if getattr(self, "conditional", False) and getattr(other, "conditional", False):
return Q(self) | Q(other)
raise NotImplementedError(
"Use .bitand(), .bitor(), and .bitxor() 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 __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(), .bitor(), and .bitxor() for bitwise logical operations."
)
def __ror__(self, other):
raise NotImplementedError(
"Use .bitand(), .bitor(), and .bitxor() for bitwise logical operations."
)
def __rxor__(self, other):
raise NotImplementedError(
"Use .bitand(), .bitor(), and .bitxor() for bitwise logical operations."
)
def __invert__(self):
return NegatedExpression(self)
class BaseExpression:
"""Base class for all query expressions."""
empty_result_set_value = NotImplemented
# aggregate specific fields
is_summary = False
_output_field_resolved_to_none = False
# Can the expression be used in a WHERE clause?
filterable = True
# Can the expression be used as a source expression in Window?
window_compatible = False
# Can the expression be used as a database default value?
allowed_default = False
def __init__(self, output_field=None):
if output_field is not None:
self.output_field = output_field
def __getstate__(self):
state = self.__dict__.copy()
state.pop("convert_value", None)
return state
def get_db_converters(self, connection):
return (
[]
if self.convert_value is self._convert_value_noop
else [self.convert_value]
) + self.output_field.get_db_converters(connection)
def get_source_expressions(self):
return []
def set_source_expressions(self, exprs):
assert not exprs
def _parse_expressions(self, *expressions):
return [
(
arg
if hasattr(arg, "resolve_expression")
else (F(arg) if isinstance(arg, str) 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().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.
Return: (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):
return any(
expr and expr.contains_aggregate for expr in self.get_source_expressions()
)
@cached_property
def contains_over_clause(self):
return any(
expr and expr.contains_over_clause for expr in self.get_source_expressions()
)
@cached_property
def contains_column_references(self):
return any(
expr and expr.contains_column_references
for expr in self.get_source_expressions()
)
@cached_property
def contains_subquery(self):
return any(
expr and (getattr(expr, "subquery", False) or expr.contains_subquery)
for expr in self.get_source_expressions()
)
def resolve_expression(
self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False
):
"""
Provide 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
Return: 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)
if expr
else None
)
for expr in c.get_source_expressions()
]
)
return c
@property
def conditional(self):
return isinstance(self.output_field, fields.BooleanField)
@property
def field(self):
return self.output_field
@cached_property
def output_field(self):
"""Return the output type of this expressions."""
output_field = self._resolve_output_field()
if output_field is None:
self._output_field_resolved_to_none = True
raise FieldError("Cannot resolve expression type, unknown output_field")
return output_field
@cached_property
def _output_field_or_none(self):
"""
Return the output field of this expression, or None if
_resolve_output_field() didn't return an output type.
"""
try:
return self.output_field
except FieldError:
if not self._output_field_resolved_to_none:
raise
def _resolve_output_field(self):
"""
Attempt to infer the output type of the expression.
As a guess, if the output fields of all source fields match then simply
infer the same type here.
If a source's output field resolves to None, exclude it from this check.
If all sources are None, then an error is raised higher up the stack in
the output_field property.
"""
# This guess is mostly a bad idea, but there is quite a lot of code
# (especially 3rd party Func subclasses) that depend on it, we'd need a
# deprecation path to fix it.
sources_iter = (
source for source in self.get_source_fields() if source is not None
)
for output_field in sources_iter:
for source in sources_iter:
if not isinstance(output_field, source.__class__):
raise FieldError(
"Expression contains mixed types: %s, %s. You must "
"set output_field."
% (
output_field.__class__.__name__,
source.__class__.__name__,
)
)
return output_field
@staticmethod
def _convert_value_noop(value, expression, connection):
return value
@cached_property
def convert_value(self):
"""
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 internal_type == "FloatField":
return lambda value, expression, connection: (
None if value is None else float(value)
)
elif internal_type.endswith("IntegerField"):
return lambda value, expression, connection: (
None if value is None else int(value)
)
elif internal_type == "DecimalField":
return lambda value, expression, connection: (
None if value is None else Decimal(value)
)
return self._convert_value_noop
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) if e is not None else None
for e in self.get_source_expressions()
]
)
return clone
def replace_expressions(self, replacements):
if not replacements:
return self
if replacement := replacements.get(self):
return replacement
if not (source_expressions := self.get_source_expressions()):
return self
clone = self.copy()
clone.set_source_expressions(
[
expr.replace_expressions(replacements) if expr else None
for expr in source_expressions
]
)
return clone
def get_refs(self):
refs = set()
for expr in self.get_source_expressions():
if expr is None:
continue
refs |= expr.get_refs()
return refs
def copy(self):
return copy.copy(self)
def prefix_references(self, prefix):
clone = self.copy()
clone.set_source_expressions(
[
(
F(f"{prefix}{expr.name}")
if isinstance(expr, F)
else expr.prefix_references(prefix)
)
for expr in self.get_source_expressions()
]
)
return clone
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):
"""Return the underlying field types used by this aggregate."""
return [e._output_field_or_none for e in self.get_source_expressions()]
def asc(self, **kwargs):
return OrderBy(self, **kwargs)
def desc(self, **kwargs):
return OrderBy(self, descending=True, **kwargs)
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:
if hasattr(expr, "flatten"):
yield from expr.flatten()
else:
yield expr
def select_format(self, compiler, sql, params):
"""
Custom format for select clauses. For example, EXISTS expressions need
to be wrapped in CASE WHEN on Oracle.
"""
if hasattr(self.output_field, "select_format"):
return self.output_field.select_format(compiler, sql, params)
return sql, params
@deconstructible
class Expression(BaseExpression, Combinable):
"""An expression that can be combined with other expressions."""
@classproperty
@functools.lru_cache(maxsize=128)
def _constructor_signature(cls):
return inspect.signature(cls.__init__)
@cached_property
def identity(self):
args, kwargs = self._constructor_args
signature = self._constructor_signature.bind_partial(self, *args, **kwargs)
signature.apply_defaults()
arguments = iter(signature.arguments.items())
next(arguments)
identity = [self.__class__]
for arg, value in arguments:
if isinstance(value, fields.Field):
if value.name and value.model:
value = (value.model._meta.label, value.name)
else:
value = type(value)
else:
value = make_hashable(value)
identity.append((arg, value))
return tuple(identity)
def __eq__(self, other):
if not isinstance(other, Expression):
return NotImplemented
return other.identity == self.identity
def __hash__(self):
return hash(self.identity)
# Type inference for CombinedExpression.output_field.
# Missing items will result in FieldError, by design.
#
# The current approach for NULL is based on lowest common denominator behavior
# i.e. if one of the supported databases is raising an error (rather than
# return NULL) for `val <op> NULL`, then Django raises FieldError.
_connector_combinations = [
# Numeric operations - operands of same type.
# PositiveIntegerField should take precedence over IntegerField (except
# subtraction).
{
connector: [
(
fields.PositiveIntegerField,
fields.PositiveIntegerField,
fields.PositiveIntegerField,
),
]
for connector in (
Combinable.ADD,
Combinable.MUL,
Combinable.DIV,
Combinable.MOD,
Combinable.POW,
)
},
# Other numeric operands.
{
connector: [
(fields.IntegerField, fields.IntegerField, fields.IntegerField),
(fields.FloatField, fields.FloatField, fields.FloatField),
(fields.DecimalField, fields.DecimalField, fields.DecimalField),
]
for connector in (
Combinable.ADD,
Combinable.SUB,
Combinable.MUL,
# Behavior for DIV with integer arguments follows Postgres/SQLite,
# not MySQL/Oracle.
Combinable.DIV,
Combinable.MOD,
Combinable.POW,
)
},
# Numeric operations - operands of different type.
{
connector: [
(fields.IntegerField, fields.DecimalField, fields.DecimalField),
(fields.DecimalField, fields.IntegerField, fields.DecimalField),
(fields.IntegerField, fields.FloatField, fields.FloatField),
(fields.FloatField, fields.IntegerField, fields.FloatField),
]
for connector in (
Combinable.ADD,
Combinable.SUB,
Combinable.MUL,
Combinable.DIV,
Combinable.MOD,
)
},
# Bitwise operators.
{
connector: [
(fields.IntegerField, fields.IntegerField, fields.IntegerField),
]
for connector in (
Combinable.BITAND,
Combinable.BITOR,
Combinable.BITLEFTSHIFT,
Combinable.BITRIGHTSHIFT,
Combinable.BITXOR,
)
},
# Numeric with NULL.
{
connector: list(
chain.from_iterable(
[(field_type, NoneType, field_type), (NoneType, field_type, field_type)]
for field_type in (
fields.IntegerField,
fields.DecimalField,
fields.FloatField,
)
)
)
for connector in (
Combinable.ADD,
Combinable.SUB,
Combinable.MUL,
Combinable.DIV,
Combinable.MOD,
Combinable.POW,
)
},
# Date/DateTimeField/DurationField/TimeField.
{
Combinable.ADD: [
# Date/DateTimeField.
(fields.DateField, fields.DurationField, fields.DateTimeField),
(fields.DateTimeField, fields.DurationField, fields.DateTimeField),
(fields.DurationField, fields.DateField, fields.DateTimeField),
(fields.DurationField, fields.DateTimeField, fields.DateTimeField),
# DurationField.
(fields.DurationField, fields.DurationField, fields.DurationField),
# TimeField.
(fields.TimeField, fields.DurationField, fields.TimeField),
(fields.DurationField, fields.TimeField, fields.TimeField),
],
},
{
Combinable.SUB: [
# Date/DateTimeField.
(fields.DateField, fields.DurationField, fields.DateTimeField),
(fields.DateTimeField, fields.DurationField, fields.DateTimeField),
(fields.DateField, fields.DateField, fields.DurationField),
(fields.DateField, fields.DateTimeField, fields.DurationField),
(fields.DateTimeField, fields.DateField, fields.DurationField),
(fields.DateTimeField, fields.DateTimeField, fields.DurationField),
# DurationField.
(fields.DurationField, fields.DurationField, fields.DurationField),
# TimeField.
(fields.TimeField, fields.DurationField, fields.TimeField),
(fields.TimeField, fields.TimeField, fields.DurationField),
],
},
]
_connector_combinators = defaultdict(list)
def register_combinable_fields(lhs, connector, rhs, result):
"""
Register combinable types:
lhs <connector> rhs -> result
e.g.
register_combinable_fields(
IntegerField, Combinable.ADD, FloatField, FloatField
)
"""
_connector_combinators[connector].append((lhs, rhs, result))
for d in _connector_combinations:
for connector, field_types in d.items():
for lhs, rhs, result in field_types:
register_combinable_fields(lhs, connector, rhs, result)
@functools.lru_cache(maxsize=128)
def _resolve_combined_type(connector, lhs_type, rhs_type):
combinators = _connector_combinators.get(connector, ())
for combinator_lhs_type, combinator_rhs_type, combined_type in combinators:
if issubclass(lhs_type, combinator_lhs_type) and issubclass(
rhs_type, combinator_rhs_type
):
return combined_type
class CombinedExpression(SQLiteNumericMixin, Expression):
def __init__(self, lhs, connector, rhs, output_field=None):
super().__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 _resolve_output_field(self):
# We avoid using super() here for reasons given in
# Expression._resolve_output_field()
combined_type = _resolve_combined_type(
self.connector,
type(self.lhs._output_field_or_none),
type(self.rhs._output_field_or_none),
)
if combined_type is None:
raise FieldError(
f"Cannot infer type of {self.connector!r} expression involving these "
f"types: {self.lhs.output_field.__class__.__name__}, "
f"{self.rhs.output_field.__class__.__name__}. You must set "
f"output_field."
)
return combined_type()
def as_sql(self, 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
):
lhs = self.lhs.resolve_expression(
query, allow_joins, reuse, summarize, for_save
)
rhs = self.rhs.resolve_expression(
query, allow_joins, reuse, summarize, for_save
)
if not isinstance(self, (DurationExpression, TemporalSubtraction)):
try:
lhs_type = lhs.output_field.get_internal_type()
except (AttributeError, FieldError):
lhs_type = None
try:
rhs_type = rhs.output_field.get_internal_type()
except (AttributeError, FieldError):
rhs_type = None
if "DurationField" in {lhs_type, rhs_type} and lhs_type != rhs_type:
return DurationExpression(
self.lhs, self.connector, self.rhs
).resolve_expression(
query,
allow_joins,
reuse,
summarize,
for_save,
)
datetime_fields = {"DateField", "DateTimeField", "TimeField"}
if (
self.connector == self.SUB
and lhs_type in datetime_fields
and lhs_type == rhs_type
):
return TemporalSubtraction(self.lhs, self.rhs).resolve_expression(
query,
allow_joins,
reuse,
summarize,
for_save,
)
c = self.copy()
c.is_summary = summarize
c.lhs = lhs
c.rhs = rhs
return c
@cached_property
def allowed_default(self):
return self.lhs.allowed_default and self.rhs.allowed_default
class DurationExpression(CombinedExpression):
def compile(self, side, compiler, connection):
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):
if connection.features.has_native_duration_field:
return super().as_sql(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
def as_sqlite(self, compiler, connection, **extra_context):
sql, params = self.as_sql(compiler, connection, **extra_context)
if self.connector in {Combinable.MUL, Combinable.DIV}:
try:
lhs_type = self.lhs.output_field.get_internal_type()
rhs_type = self.rhs.output_field.get_internal_type()
except (AttributeError, FieldError):
pass
else:
allowed_fields = {
"DecimalField",
"DurationField",
"FloatField",
"IntegerField",
}
if lhs_type not in allowed_fields or rhs_type not in allowed_fields:
raise DatabaseError(
f"Invalid arguments for operator {self.connector}."
)
return sql, params
class TemporalSubtraction(CombinedExpression):
output_field = fields.DurationField()
def __init__(self, lhs, rhs):
super().__init__(lhs, self.SUB, rhs)
def as_sql(self, compiler, connection):
connection.ops.check_expression_support(self)
lhs = compiler.compile(self.lhs)
rhs = compiler.compile(self.rhs)
return connection.ops.subtract_temporals(
self.lhs.output_field.get_internal_type(), lhs, rhs
)
@deconstructible(path="django.db.models.F")
class F(Combinable):
"""An object capable of resolving references to existing query objects."""
allowed_default = False
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 __getitem__(self, subscript):
return Sliced(self, subscript)
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 replace_expressions(self, replacements):
return replacements.get(self, self)
def asc(self, **kwargs):
return OrderBy(self, **kwargs)
def desc(self, **kwargs):
return OrderBy(self, descending=True, **kwargs)
def __eq__(self, other):
return self.__class__ == other.__class__ and self.name == other.name
def __hash__(self):
return hash(self.name)
def copy(self):
return copy.copy(self)
class ResolvedOuterRef(F):
"""
An object that contains a reference to an outer query.
In this case, the reference to the outer query has been resolved because
the inner query has been used as a subquery.
"""
contains_aggregate = False
contains_over_clause = False
def as_sql(self, *args, **kwargs):
raise ValueError(
"This queryset contains a reference to an outer query and may "
"only be used in a subquery."
)
def resolve_expression(self, *args, **kwargs):
col = super().resolve_expression(*args, **kwargs)
if col.contains_over_clause:
raise NotSupportedError(
f"Referencing outer query window expression is not supported: "
f"{self.name}."
)
# FIXME: Rename possibly_multivalued to multivalued and fix detection
# for non-multivalued JOINs (e.g. foreign key fields). This should take
# into account only many-to-many and one-to-many relationships.
col.possibly_multivalued = LOOKUP_SEP in self.name
return col
def relabeled_clone(self, relabels):
return self
def get_group_by_cols(self):
return []
class OuterRef(F):
contains_aggregate = False
contains_over_clause = False
def resolve_expression(self, *args, **kwargs):
if isinstance(self.name, self.__class__):
return self.name
return ResolvedOuterRef(self.name)
def relabeled_clone(self, relabels):
return self
class Sliced(F):
"""
An object that contains a slice of an F expression.
Object resolves the column on which the slicing is applied, and then
applies the slicing if possible.
"""
def __init__(self, obj, subscript):
super().__init__(obj.name)
self.obj = obj
if isinstance(subscript, int):
if subscript < 0:
raise ValueError("Negative indexing is not supported.")
self.start = subscript + 1
self.length = 1
elif isinstance(subscript, slice):
if (subscript.start is not None and subscript.start < 0) or (
subscript.stop is not None and subscript.stop < 0
):
raise ValueError("Negative indexing is not supported.")
if subscript.step is not None:
raise ValueError("Step argument is not supported.")
if subscript.stop and subscript.start and subscript.stop < subscript.start:
raise ValueError("Slice stop must be greater than slice start.")
self.start = 1 if subscript.start is None else subscript.start + 1
if subscript.stop is None:
self.length = None
else:
self.length = subscript.stop - (subscript.start or 0)
else:
raise TypeError("Argument to slice must be either int or slice instance.")
def __repr__(self):
start = self.start - 1
stop = None if self.length is None else start + self.length
subscript = slice(start, stop)
return f"{self.__class__.__qualname__}({self.obj!r}, {subscript!r})"
def resolve_expression(
self,
query=None,
allow_joins=True,
reuse=None,
summarize=False,
for_save=False,
):
resolved = query.resolve_ref(self.name, allow_joins, reuse, summarize)
if isinstance(self.obj, (OuterRef, self.__class__)):
expr = self.obj.resolve_expression(
query, allow_joins, reuse, summarize, for_save
)
else:
expr = resolved
return resolved.output_field.slice_expression(expr, self.start, self.length)
@deconstructible(path="django.db.models.Func")
class Func(SQLiteNumericMixin, Expression):
"""An SQL function call."""
function = None
template = "%(function)s(%(expressions)s)"
arg_joiner = ", "
arity = None # The number of arguments the function accepts.
def __init__(self, *expressions, output_field=None, **extra):
if self.arity is not None and len(expressions) != self.arity:
raise TypeError(
"'%s' takes exactly %s %s (%s given)"
% (
self.__class__.__name__,
self.arity,
"argument" if self.arity == 1 else "arguments",
len(expressions),
)
)
super().__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 = {**self.extra, **self._get_repr_options()}
if extra:
extra = ", ".join(
str(key) + "=" + str(val) for key, val in sorted(extra.items())
)
return "{}({}, {})".format(self.__class__.__name__, args, extra)
return "{}({})".format(self.__class__.__name__, args)
def _get_repr_options(self):
"""Return a dict of extra __init__() options to include in the repr."""
return {}
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,
arg_joiner=None,
**extra_context,
):
connection.ops.check_expression_support(self)
sql_parts = []
params = []
for arg in self.source_expressions:
try:
arg_sql, arg_params = compiler.compile(arg)
except EmptyResultSet:
empty_result_set_value = getattr(
arg, "empty_result_set_value", NotImplemented
)
if empty_result_set_value is NotImplemented:
raise
arg_sql, arg_params = compiler.compile(Value(empty_result_set_value))
except FullResultSet:
arg_sql, arg_params = compiler.compile(Value(True))
sql_parts.append(arg_sql)
params.extend(arg_params)
data = {**self.extra, **extra_context}
# Use the first supplied value in this order: the parameter to this
# method, a value supplied in __init__()'s **extra (the value in
# `data`), or the value defined on the class.
if function is not None:
data["function"] = function
else:
data.setdefault("function", self.function)
template = template or data.get("template", self.template)
arg_joiner = arg_joiner or data.get("arg_joiner", self.arg_joiner)
data["expressions"] = data["field"] = arg_joiner.join(sql_parts)
return template % data, params
def copy(self):
copy = super().copy()
copy.source_expressions = self.source_expressions[:]
copy.extra = self.extra.copy()
return copy
@cached_property
def allowed_default(self):
return all(expression.allowed_default for expression in self.source_expressions)
@deconstructible(path="django.db.models.Value")
class Value(SQLiteNumericMixin, Expression):
"""Represent a wrapped value as a node within an expression."""
# Provide a default value for `for_save` in order to allow unresolved
# instances to be compiled until a decision is taken in #25425.
for_save = False
allowed_default = True
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().__init__(output_field=output_field)
self.value = value
def __repr__(self):
return f"{self.__class__.__name__}({self.value!r})"
def as_sql(self, compiler, connection):
connection.ops.check_expression_support(self)
val = self.value
output_field = self._output_field_or_none
if output_field is not None:
if self.for_save:
val = output_field.get_db_prep_save(val, connection=connection)
else:
val = output_field.get_db_prep_value(val, connection=connection)
if hasattr(output_field, "get_placeholder"):
return output_field.get_placeholder(val, compiler, connection), [val]
if val is None:
# oracledb 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().resolve_expression(query, allow_joins, reuse, summarize, for_save)
c.for_save = for_save
return c
def get_group_by_cols(self):
return []
def _resolve_output_field(self):
if isinstance(self.value, str):
return fields.CharField()
if isinstance(self.value, bool):
return fields.BooleanField()
if isinstance(self.value, int):
return fields.IntegerField()
if isinstance(self.value, float):
return fields.FloatField()
if isinstance(self.value, datetime.datetime):
return fields.DateTimeField()
if isinstance(self.value, datetime.date):
return fields.DateField()
if isinstance(self.value, datetime.time):
return fields.TimeField()
if isinstance(self.value, datetime.timedelta):
return fields.DurationField()
if isinstance(self.value, Decimal):
return fields.DecimalField()
if isinstance(self.value, bytes):
return fields.BinaryField()
if isinstance(self.value, UUID):
return fields.UUIDField()
@property
def empty_result_set_value(self):
return self.value
class RawSQL(Expression):
allowed_default = True
def __init__(self, sql, params, output_field=None):
if output_field is None:
output_field = fields.Field()
self.sql, self.params = sql, params
super().__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]
def resolve_expression(
self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False
):
# Resolve parents fields used in raw SQL.
if query.model:
for parent in query.model._meta.all_parents:
for parent_field in parent._meta.local_fields:
if parent_field.column.lower() in self.sql.lower():
query.resolve_ref(
parent_field.name, allow_joins, reuse, summarize
)
break
return super().resolve_expression(
query, allow_joins, reuse, summarize, for_save
)
class Star(Expression):
def __repr__(self):
return "'*'"
def as_sql(self, compiler, connection):
return "*", []
class DatabaseDefault(Expression):
"""Placeholder expression for the database default in an insert query."""
def as_sql(self, compiler, connection):
return "DEFAULT", []
class Col(Expression):
contains_column_references = True
possibly_multivalued = False
def __init__(self, alias, target, output_field=None):
if output_field is None:
output_field = target
super().__init__(output_field=output_field)
self.alias, self.target = alias, target
def __repr__(self):
alias, target = self.alias, self.target
identifiers = (alias, str(target)) if alias else (str(target),)
return "{}({})".format(self.__class__.__name__, ", ".join(identifiers))
def as_sql(self, compiler, connection):
alias, column = self.alias, self.target.column
identifiers = (alias, column) if alias else (column,)
sql = ".".join(map(compiler.quote_name_unless_alias, identifiers))
return sql, []
def relabeled_clone(self, relabels):
if self.alias is None:
return self
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().__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 get_refs(self):
return {self.refs}
def relabeled_clone(self, relabels):
clone = self.copy()
clone.source = self.source.relabeled_clone(relabels)
return clone
def as_sql(self, compiler, connection):
return connection.ops.quote_name(self.refs), []
def get_group_by_cols(self):
return [self]
class ExpressionList(Func):
"""
An expression containing multiple expressions. Can be used to provide a
list of expressions as an argument to another expression, like a partition
clause.
"""
template = "%(expressions)s"
def __init__(self, *expressions, **extra):
if not expressions:
raise ValueError(
"%s requires at least one expression." % self.__class__.__name__
)
super().__init__(*expressions, **extra)
def __str__(self):
return self.arg_joiner.join(str(arg) for arg in self.source_expressions)
def as_sqlite(self, compiler, connection, **extra_context):
# Casting to numeric is unnecessary.
return self.as_sql(compiler, connection, **extra_context)
def get_group_by_cols(self):
group_by_cols = []
for expr in self.get_source_expressions():
group_by_cols.extend(expr.get_group_by_cols())
return group_by_cols
class OrderByList(ExpressionList):
allowed_default = False
template = "ORDER BY %(expressions)s"
def __init__(self, *expressions, **extra):
expressions = (
(
OrderBy(F(expr[1:]), descending=True)
if isinstance(expr, str) and expr[0] == "-"
else expr
)
for expr in expressions
)
super().__init__(*expressions, **extra)
@deconstructible(path="django.db.models.ExpressionWrapper")
class ExpressionWrapper(SQLiteNumericMixin, 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().__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 get_group_by_cols(self):
if isinstance(self.expression, Expression):
expression = self.expression.copy()
expression.output_field = self.output_field
return expression.get_group_by_cols()
# For non-expressions e.g. an SQL WHERE clause, the entire
# `expression` must be included in the GROUP BY clause.
return super().get_group_by_cols()
def as_sql(self, compiler, connection):
return compiler.compile(self.expression)
def __repr__(self):
return "{}({})".format(self.__class__.__name__, self.expression)
@property
def allowed_default(self):
return self.expression.allowed_default
class NegatedExpression(ExpressionWrapper):
"""The logical negation of a conditional expression."""
def __init__(self, expression):
super().__init__(expression, output_field=fields.BooleanField())
def __invert__(self):
return self.expression.copy()
def as_sql(self, compiler, connection):
try:
sql, params = super().as_sql(compiler, connection)
except EmptyResultSet:
features = compiler.connection.features
if not features.supports_boolean_expr_in_select_clause:
return "1=1", ()
return compiler.compile(Value(True))
ops = compiler.connection.ops
# Some database backends (e.g. Oracle) don't allow EXISTS() and filters
# to be compared to another expression unless they're wrapped in a CASE
# WHEN.
if not ops.conditional_expression_supported_in_where_clause(self.expression):
return f"CASE WHEN {sql} = 0 THEN 1 ELSE 0 END", params
return f"NOT {sql}", params
def resolve_expression(
self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False
):
resolved = super().resolve_expression(
query, allow_joins, reuse, summarize, for_save
)
if not getattr(resolved.expression, "conditional", False):
raise TypeError("Cannot negate non-conditional expressions.")
return resolved
def select_format(self, compiler, sql, params):
# Wrap boolean expressions with a CASE WHEN expression if a database
# backend (e.g. Oracle) doesn't support boolean expression in SELECT or
# GROUP BY list.
expression_supported_in_where_clause = (
compiler.connection.ops.conditional_expression_supported_in_where_clause
)
if (
not compiler.connection.features.supports_boolean_expr_in_select_clause
# Avoid double wrapping.
and expression_supported_in_where_clause(self.expression)
):
sql = "CASE WHEN {} THEN 1 ELSE 0 END".format(sql)
return sql, params
@deconstructible(path="django.db.models.When")
class When(Expression):
template = "WHEN %(condition)s THEN %(result)s"
# This isn't a complete conditional expression, must be used in Case().
conditional = False
def __init__(self, condition=None, then=None, **lookups):
if lookups:
if condition is None:
condition, lookups = Q(**lookups), None
elif getattr(condition, "conditional", False):
condition, lookups = Q(condition, **lookups), None
if condition is None or not getattr(condition, "conditional", False) or lookups:
raise TypeError(
"When() supports a Q object, a boolean expression, or lookups "
"as a condition."
)
if isinstance(condition, Q) and not condition:
raise ValueError("An empty Q() can't be used as a When() condition.")
super().__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, **extra_context):
connection.ops.check_expression_support(self)
template_params = extra_context
sql_params = []
condition_sql, condition_params = compiler.compile(self.condition)
template_params["condition"] = condition_sql
result_sql, result_params = compiler.compile(self.result)
template_params["result"] = result_sql
template = template or self.template
return template % template_params, (
*sql_params,
*condition_params,
*result_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
@cached_property
def allowed_default(self):
return self.condition.allowed_default and self.result.allowed_default
@deconstructible(path="django.db.models.Case")
class Case(SQLiteNumericMixin, 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, default=None, output_field=None, **extra):
if not all(isinstance(case, When) for case in cases):
raise TypeError("Positional arguments must all be When objects.")
super().__init__(output_field)
self.cases = list(cases)
self.default = self._parse_expressions(default)[0]
self.extra = extra
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, self.default = 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, 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().copy()
c.cases = c.cases[:]
return c
def as_sql(
self, compiler, connection, template=None, case_joiner=None, **extra_context
):
connection.ops.check_expression_support(self)
if not self.cases:
return compiler.compile(self.default)
template_params = {**self.extra, **extra_context}
case_parts = []
sql_params = []
default_sql, default_params = compiler.compile(self.default)
for case in self.cases:
try:
case_sql, case_params = compiler.compile(case)
except EmptyResultSet:
continue
except FullResultSet:
default_sql, default_params = compiler.compile(case.result)
break
case_parts.append(case_sql)
sql_params.extend(case_params)
if not case_parts:
return default_sql, default_params
case_joiner = case_joiner or self.case_joiner
template_params["cases"] = case_joiner.join(case_parts)
template_params["default"] = default_sql
sql_params.extend(default_params)
template = template or template_params.get("template", 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
def get_group_by_cols(self):
if not self.cases:
return self.default.get_group_by_cols()
return super().get_group_by_cols()
@cached_property
def allowed_default(self):
return self.default.allowed_default and all(
case_.allowed_default for case_ in self.cases
)
class Subquery(BaseExpression, Combinable):
"""
An explicit subquery. It may contain OuterRef() references to the outer
query which will be resolved when it is applied to that query.
"""
template = "(%(subquery)s)"
contains_aggregate = False
empty_result_set_value = None
subquery = True
def __init__(self, queryset, output_field=None, **extra):
# Allow the usage of both QuerySet and sql.Query objects.
self.query = getattr(queryset, "query", queryset).clone()
self.query.subquery = True
self.extra = extra
super().__init__(output_field)
def get_source_expressions(self):
return [self.query]
def set_source_expressions(self, exprs):
self.query = exprs[0]
def _resolve_output_field(self):
return self.query.output_field
def copy(self):
clone = super().copy()
clone.query = clone.query.clone()
return clone
@property
def external_aliases(self):
return self.query.external_aliases
def get_external_cols(self):
return self.query.get_external_cols()
def as_sql(self, compiler, connection, template=None, **extra_context):
connection.ops.check_expression_support(self)
template_params = {**self.extra, **extra_context}
subquery_sql, sql_params = self.query.as_sql(compiler, connection)
template_params["subquery"] = subquery_sql[1:-1]
template = template or template_params.get("template", self.template)
sql = template % template_params
return sql, sql_params
def get_group_by_cols(self):
return self.query.get_group_by_cols(wrapper=self)
class Exists(Subquery):
template = "EXISTS(%(subquery)s)"
output_field = fields.BooleanField()
empty_result_set_value = False
def __init__(self, queryset, **kwargs):
super().__init__(queryset, **kwargs)
self.query = self.query.exists()
def select_format(self, compiler, sql, params):
# Wrap EXISTS() with a CASE WHEN expression if a database backend
# (e.g. Oracle) doesn't support boolean expression in SELECT or GROUP
# BY list.
if not compiler.connection.features.supports_boolean_expr_in_select_clause:
sql = "CASE WHEN {} THEN 1 ELSE 0 END".format(sql)
return sql, params
def as_sql(self, compiler, *args, **kwargs):
try:
return super().as_sql(compiler, *args, **kwargs)
except EmptyResultSet:
features = compiler.connection.features
if not features.supports_boolean_expr_in_select_clause:
return "1=0", ()
return compiler.compile(Value(False))
@deconstructible(path="django.db.models.OrderBy")
class OrderBy(Expression):
template = "%(expression)s %(ordering)s"
conditional = False
def __init__(self, expression, descending=False, nulls_first=None, nulls_last=None):
if nulls_first and nulls_last:
raise ValueError("nulls_first and nulls_last are mutually exclusive")
if nulls_first is False or nulls_last is False:
raise ValueError("nulls_first and nulls_last values must be True or None.")
self.nulls_first = nulls_first
self.nulls_last = nulls_last
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, template=None, **extra_context):
template = template or self.template
if connection.features.supports_order_by_nulls_modifier:
if self.nulls_last:
template = "%s NULLS LAST" % template
elif self.nulls_first:
template = "%s NULLS FIRST" % template
else:
if self.nulls_last and not (
self.descending and connection.features.order_by_nulls_first
):
template = "%%(expression)s IS NULL, %s" % template
elif self.nulls_first and not (
not self.descending and connection.features.order_by_nulls_first
):
template = "%%(expression)s IS NOT NULL, %s" % template
connection.ops.check_expression_support(self)
expression_sql, params = compiler.compile(self.expression)
placeholders = {
"expression": expression_sql,
"ordering": "DESC" if self.descending else "ASC",
**extra_context,
}
params *= template.count("%(expression)s")
return (template % placeholders).rstrip(), params
def as_oracle(self, compiler, connection):
# Oracle < 23c doesn't allow ORDER BY EXISTS() or filters unless it's
# wrapped in a CASE WHEN.
if (
not connection.features.supports_boolean_expr_in_select_clause
and connection.ops.conditional_expression_supported_in_where_clause(
self.expression
)
):
copy = self.copy()
copy.expression = Case(
When(self.expression, then=True),
default=False,
)
return copy.as_sql(compiler, connection)
return self.as_sql(compiler, connection)
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
if self.nulls_first:
self.nulls_last = True
self.nulls_first = None
elif self.nulls_last:
self.nulls_first = True
self.nulls_last = None
return self
def asc(self):
self.descending = False
def desc(self):
self.descending = True
class Window(SQLiteNumericMixin, Expression):
template = "%(expression)s OVER (%(window)s)"
# Although the main expression may either be an aggregate or an
# expression with an aggregate function, the GROUP BY that will
# be introduced in the query as a result is not desired.
contains_aggregate = False
contains_over_clause = True
def __init__(
self,
expression,
partition_by=None,
order_by=None,
frame=None,
output_field=None,
):
self.partition_by = partition_by
self.order_by = order_by
self.frame = frame
if not getattr(expression, "window_compatible", False):
raise ValueError(
"Expression '%s' isn't compatible with OVER clauses."
% expression.__class__.__name__
)
if self.partition_by is not None:
if not isinstance(self.partition_by, (tuple, list)):
self.partition_by = (self.partition_by,)
self.partition_by = ExpressionList(*self.partition_by)
if self.order_by is not None:
if isinstance(self.order_by, (list, tuple)):
self.order_by = OrderByList(*self.order_by)
elif isinstance(self.order_by, (BaseExpression, str)):
self.order_by = OrderByList(self.order_by)
else:
raise ValueError(
"Window.order_by must be either a string reference to a "
"field, an expression, or a list or tuple of them."
)
super().__init__(output_field=output_field)
self.source_expression = self._parse_expressions(expression)[0]
def _resolve_output_field(self):
return self.source_expression.output_field
def get_source_expressions(self):
return [self.source_expression, self.partition_by, self.order_by, self.frame]
def set_source_expressions(self, exprs):
self.source_expression, self.partition_by, self.order_by, self.frame = exprs
def as_sql(self, compiler, connection, template=None):
connection.ops.check_expression_support(self)
if not connection.features.supports_over_clause:
raise NotSupportedError("This backend does not support window expressions.")
expr_sql, params = compiler.compile(self.source_expression)
window_sql, window_params = [], ()
if self.partition_by is not None:
sql_expr, sql_params = self.partition_by.as_sql(
compiler=compiler,
connection=connection,
template="PARTITION BY %(expressions)s",
)
window_sql.append(sql_expr)
window_params += tuple(sql_params)
if self.order_by is not None:
order_sql, order_params = compiler.compile(self.order_by)
window_sql.append(order_sql)
window_params += tuple(order_params)
if self.frame:
frame_sql, frame_params = compiler.compile(self.frame)
window_sql.append(frame_sql)
window_params += tuple(frame_params)
template = template or self.template
return (
template % {"expression": expr_sql, "window": " ".join(window_sql).strip()},
(*params, *window_params),
)
def as_sqlite(self, compiler, connection):
if isinstance(self.output_field, fields.DecimalField):
# Casting to numeric must be outside of the window expression.
copy = self.copy()
source_expressions = copy.get_source_expressions()
source_expressions[0].output_field = fields.FloatField()
copy.set_source_expressions(source_expressions)
return super(Window, copy).as_sqlite(compiler, connection)
return self.as_sql(compiler, connection)
def __str__(self):
return "{} OVER ({}{}{})".format(
str(self.source_expression),
"PARTITION BY " + str(self.partition_by) if self.partition_by else "",
str(self.order_by or ""),
str(self.frame or ""),
)
def __repr__(self):
return "<%s: %s>" % (self.__class__.__name__, self)
def get_group_by_cols(self):
group_by_cols = []
if self.partition_by:
group_by_cols.extend(self.partition_by.get_group_by_cols())
if self.order_by is not None:
group_by_cols.extend(self.order_by.get_group_by_cols())
return group_by_cols
class WindowFrameExclusion(Enum):
CURRENT_ROW = "CURRENT ROW"
GROUP = "GROUP"
TIES = "TIES"
NO_OTHERS = "NO OTHERS"
def __repr__(self):
return f"{self.__class__.__qualname__}.{self._name_}"
class WindowFrame(Expression):
"""
Model the frame clause in window expressions. There are two types of frame
clauses which are subclasses, however, all processing and validation (by no
means intended to be complete) is done here. Thus, providing an end for a
frame is optional (the default is UNBOUNDED FOLLOWING, which is the last
row in the frame).
"""
template = "%(frame_type)s BETWEEN %(start)s AND %(end)s%(exclude)s"
def __init__(self, start=None, end=None, exclusion=None):
self.start = Value(start)
self.end = Value(end)
if not isinstance(exclusion, (NoneType, WindowFrameExclusion)):
raise TypeError(
f"{self.__class__.__qualname__}.exclusion must be a "
"WindowFrameExclusion instance."
)
self.exclusion = exclusion
def set_source_expressions(self, exprs):
self.start, self.end = exprs
def get_source_expressions(self):
return [self.start, self.end]
def get_exclusion(self):
if self.exclusion is None:
return ""
return f" EXCLUDE {self.exclusion.value}"
def as_sql(self, compiler, connection):
connection.ops.check_expression_support(self)
start, end = self.window_frame_start_end(
connection, self.start.value, self.end.value
)
if self.exclusion and not connection.features.supports_frame_exclusion:
raise NotSupportedError(
"This backend does not support window frame exclusions."
)
return (
self.template
% {
"frame_type": self.frame_type,
"start": start,
"end": end,
"exclude": self.get_exclusion(),
},
[],
)
def __repr__(self):
return "<%s: %s>" % (self.__class__.__name__, self)
def get_group_by_cols(self):
return []
def __str__(self):
if self.start.value is not None and self.start.value < 0:
start = "%d %s" % (abs(self.start.value), connection.ops.PRECEDING)
elif self.start.value is not None and self.start.value == 0:
start = connection.ops.CURRENT_ROW
elif self.start.value is not None and self.start.value > 0:
start = "%d %s" % (self.start.value, connection.ops.FOLLOWING)
else:
start = connection.ops.UNBOUNDED_PRECEDING
if self.end.value is not None and self.end.value > 0:
end = "%d %s" % (self.end.value, connection.ops.FOLLOWING)
elif self.end.value is not None and self.end.value == 0:
end = connection.ops.CURRENT_ROW
elif self.end.value is not None and self.end.value < 0:
end = "%d %s" % (abs(self.end.value), connection.ops.PRECEDING)
else:
end = connection.ops.UNBOUNDED_FOLLOWING
return self.template % {
"frame_type": self.frame_type,
"start": start,
"end": end,
"exclude": self.get_exclusion(),
}
def window_frame_start_end(self, connection, start, end):
raise NotImplementedError("Subclasses must implement window_frame_start_end().")
class RowRange(WindowFrame):
frame_type = "ROWS"
def window_frame_start_end(self, connection, start, end):
return connection.ops.window_frame_rows_start_end(start, end)
class ValueRange(WindowFrame):
frame_type = "RANGE"
def window_frame_start_end(self, connection, start, end):
return connection.ops.window_frame_range_start_end(start, end)