class Variance

Attributes
Methods

from django.db.models.aggregates import Variance

Ancestors (MRO)

builtins.object
django.db.models.expressions.Combinable
django.db.models.expressions.BaseExpression
django.db.models.expressions.Expression
django.db.models.expressions.SQLiteNumericMixin
django.db.models.expressions.Func
django.db.models.aggregates.Aggregate
django.db.models.functions.mixins.NumericOutputFieldMixin
django.db.models.aggregates.Variance

Attributes

Attribute	Value	Defined in
`ADD`	`+`	django.db.models.expressions.Combinable
`BITAND`	`&`	django.db.models.expressions.Combinable
`BITLEFTSHIFT`	`<<`	django.db.models.expressions.Combinable
`BITOR`	`\|`	django.db.models.expressions.Combinable
`BITRIGHTSHIFT`	`>>`	django.db.models.expressions.Combinable
`BITXOR`	`#`	django.db.models.expressions.Combinable
`DIV`	`/`	django.db.models.expressions.Combinable
`MOD`	`%%`	django.db.models.expressions.Combinable
`MUL`	`*`	django.db.models.expressions.Combinable
`POW`	`^`	django.db.models.expressions.Combinable
`SUB`	`-`	django.db.models.expressions.Combinable
`allow_distinct`	`False`	django.db.models.aggregates.Aggregate
`allowed_default`	`False`	django.db.models.expressions.BaseExpression
`arg_joiner`	`,`	django.db.models.expressions.Func
`arity`	`None`	django.db.models.expressions.Func
`contains_aggregate`	`True`	django.db.models.aggregates.Aggregate
`empty_result_set_value`	`None`	django.db.models.aggregates.Aggregate
`empty_result_set_value`	`NotImplemented`	django.db.models.expressions.BaseExpression
`filter_template`	`%s FILTER (WHERE %%(filter)s)`	django.db.models.aggregates.Aggregate
`filterable`	`True`	django.db.models.expressions.BaseExpression
`function`	`None`	django.db.models.expressions.Func
`is_summary`	`False`	django.db.models.expressions.BaseExpression
`name`	`Variance`	django.db.models.aggregates.Variance
`name`	`None`	django.db.models.aggregates.Aggregate
`template`	`%(function)s(%(distinct)s%(expressions)s)`	django.db.models.aggregates.Aggregate
`template`	`%(function)s(%(expressions)s)`	django.db.models.expressions.Func
`window_compatible`	`True`	django.db.models.aggregates.Aggregate
`window_compatible`	`False`	django.db.models.expressions.BaseExpression

Methods

def allowed_default(self)

django.db.models.expressions.Func

def as_sql(self, compiler, connection, **extra_context)

django.db.models.aggregates.Aggregate

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`.

    def as_sql(self, compiler, connection, **extra_context):
        extra_context["distinct"] = "DISTINCT " if self.distinct else ""
        if self.filter:
            if connection.features.supports_aggregate_filter_clause:
                try:
                    filter_sql, filter_params = self.filter.as_sql(compiler, connection)
                except FullResultSet:
                    pass
                else:
                    template = self.filter_template % extra_context.get(
                        "template", self.template
                    )
                    sql, params = super().as_sql(
                        compiler,
                        connection,
                        template=template,
                        filter=filter_sql,
                        **extra_context,
                    )
                    return sql, (*params, *filter_params)
            else:
                copy = self.copy()
                copy.filter = None
                source_expressions = copy.get_source_expressions()
                condition = When(self.filter, then=source_expressions[0])
                copy.set_source_expressions([Case(condition)] + source_expressions[1:])
                return super(Aggregate, copy).as_sql(
                    compiler, connection, **extra_context
                )
        return super().as_sql(compiler, connection, **extra_context)

django.db.models.expressions.Func

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`.

    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

django.db.models.expressions.BaseExpression

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`.

    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()")

def as_sqlite(self, compiler, connection, **extra_context)

django.db.models.expressions.SQLiteNumericMixin

    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

def asc(self, **kwargs)

django.db.models.expressions.BaseExpression

    def asc(self, **kwargs):
        return OrderBy(self, **kwargs)

def bitand(self, other)

django.db.models.expressions.Combinable

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

def bitleftshift(self, other)

django.db.models.expressions.Combinable

    def bitleftshift(self, other):
        return self._combine(other, self.BITLEFTSHIFT, False)

def bitor(self, other)

django.db.models.expressions.Combinable

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

def bitrightshift(self, other)

django.db.models.expressions.Combinable

    def bitrightshift(self, other):
        return self._combine(other, self.BITRIGHTSHIFT, False)

def bitxor(self, other)

django.db.models.expressions.Combinable

    def bitxor(self, other):
        return self._combine(other, self.BITXOR, False)

def conditional(self)

django.db.models.expressions.BaseExpression

def contains_aggregate(self)

django.db.models.expressions.BaseExpression

def contains_column_references(self)

django.db.models.expressions.BaseExpression

def contains_over_clause(self)

django.db.models.expressions.BaseExpression

def contains_subquery(self)

django.db.models.expressions.BaseExpression

def convert_value(self)

django.db.models.expressions.BaseExpression

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.

def copy(self)

django.db.models.expressions.Func

    def copy(self):
        copy = super().copy()
        copy.source_expressions = self.source_expressions[:]
        copy.extra = self.extra.copy()
        return copy

django.db.models.expressions.BaseExpression

    def copy(self):
        return copy.copy(self)

def deconstruct(obj)

django.db.models.expressions.Func

Return a 3-tuple of class import path, positional arguments,
and keyword arguments.

        def deconstruct(obj):
            """
            Return a 3-tuple of class import path, positional arguments,
            and keyword arguments.
            """
            # Fallback version
            if path and type(obj) is klass:
                module_name, _, name = path.rpartition(".")
            else:
                module_name = obj.__module__
                name = obj.__class__.__name__
            # Make sure it's actually there and not an inner class
            module = import_module(module_name)
            if not hasattr(module, name):
                raise ValueError(
                    "Could not find object %s in %s.\n"
                    "Please note that you cannot serialize things like inner "
                    "classes. Please move the object into the main module "
                    "body to use migrations.\n"
                    "For more information, see "
                    "https://docs.djangoproject.com/en/%s/topics/migrations/"
                    "#serializing-values" % (name, module_name, get_docs_version())
                )
            return (
                (
                    path
                    if path and type(obj) is klass
                    else f"{obj.__class__.__module__}.{name}"
                ),
                obj._constructor_args[0],
                obj._constructor_args[1],
            )

django.db.models.expressions.Expression

Return a 3-tuple of class import path, positional arguments,
and keyword arguments.

        def deconstruct(obj):
            """
            Return a 3-tuple of class import path, positional arguments,
            and keyword arguments.
            """
            # Fallback version
            if path and type(obj) is klass:
                module_name, _, name = path.rpartition(".")
            else:
                module_name = obj.__module__
                name = obj.__class__.__name__
            # Make sure it's actually there and not an inner class
            module = import_module(module_name)
            if not hasattr(module, name):
                raise ValueError(
                    "Could not find object %s in %s.\n"
                    "Please note that you cannot serialize things like inner "
                    "classes. Please move the object into the main module "
                    "body to use migrations.\n"
                    "For more information, see "
                    "https://docs.djangoproject.com/en/%s/topics/migrations/"
                    "#serializing-values" % (name, module_name, get_docs_version())
                )
            return (
                (
                    path
                    if path and type(obj) is klass
                    else f"{obj.__class__.__module__}.{name}"
                ),
                obj._constructor_args[0],
                obj._constructor_args[1],
            )

def default_alias(self)

django.db.models.aggregates.Aggregate

def desc(self, **kwargs)

django.db.models.expressions.BaseExpression

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

def field(self)

django.db.models.expressions.BaseExpression

def flatten(self)

django.db.models.expressions.BaseExpression

Recursively yield this expression and all subexpressions, in
depth-first order.

    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 get_db_converters(self, connection)

django.db.models.expressions.BaseExpression

    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_group_by_cols(self)

django.db.models.aggregates.Aggregate

    def get_group_by_cols(self):
        return []

django.db.models.expressions.BaseExpression

    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_lookup(self, lookup)

django.db.models.expressions.BaseExpression

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

def get_refs(self)

django.db.models.expressions.BaseExpression

    def get_refs(self):
        refs = set()
        for expr in self.get_source_expressions():
            refs |= expr.get_refs()
        return refs

def get_source_expressions(self)

django.db.models.aggregates.Aggregate

    def get_source_expressions(self):
        source_expressions = super().get_source_expressions()
        if self.filter:
            return source_expressions + [self.filter]
        return source_expressions

django.db.models.expressions.Func

    def get_source_expressions(self):
        return self.source_expressions

django.db.models.expressions.BaseExpression

    def get_source_expressions(self):
        return []

def get_source_fields(self)

django.db.models.aggregates.Aggregate

Return the underlying field types used by this aggregate.

    def get_source_fields(self):
        # Don't return the filter expression since it's not a source field.
        return [e._output_field_or_none for e in super().get_source_expressions()]

django.db.models.expressions.BaseExpression

Return the underlying field types used by this aggregate.

    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 get_transform(self, name)

django.db.models.expressions.BaseExpression

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

def identity(self)

django.db.models.expressions.Expression

def output_field(self)

django.db.models.expressions.BaseExpression

Return the output type of this expressions.

def prefix_references(self, prefix)

django.db.models.expressions.BaseExpression

    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 relabeled_clone(self, change_map)

django.db.models.expressions.BaseExpression

    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)

django.db.models.expressions.BaseExpression

    def replace_expressions(self, replacements):
        if replacement := replacements.get(self):
            return replacement
        clone = self.copy()
        source_expressions = clone.get_source_expressions()
        clone.set_source_expressions(
            [
                expr.replace_expressions(replacements) if expr else None
                for expr in source_expressions
            ]
        )
        return clone

def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False)

django.db.models.aggregates.Aggregate

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.

    def resolve_expression(
        self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False
    ):
        # Aggregates are not allowed in UPDATE queries, so ignore for_save
        c = super().resolve_expression(query, allow_joins, reuse, summarize)
        c.filter = c.filter and c.filter.resolve_expression(
            query, allow_joins, reuse, summarize
        )
        if summarize:
            # Summarized aggregates cannot refer to summarized aggregates.
            for ref in c.get_refs():
                if query.annotations[ref].is_summary:
                    raise FieldError(
                        f"Cannot compute {c.name}('{ref}'): '{ref}' is an aggregate"
                    )
        elif not self.is_summary:
            # Call Aggregate.get_source_expressions() to avoid
            # returning self.filter and including that in this loop.
            expressions = super(Aggregate, c).get_source_expressions()
            for index, expr in enumerate(expressions):
                if expr.contains_aggregate:
                    before_resolved = self.get_source_expressions()[index]
                    name = (
                        before_resolved.name
                        if hasattr(before_resolved, "name")
                        else repr(before_resolved)
                    )
                    raise FieldError(
                        "Cannot compute %s('%s'): '%s' is an aggregate"
                        % (c.name, name, name)
                    )
        if (default := c.default) is None:
            return c
        if hasattr(default, "resolve_expression"):
            default = default.resolve_expression(query, allow_joins, reuse, summarize)
            if default._output_field_or_none is None:
                default.output_field = c._output_field_or_none
        else:
            default = Value(default, c._output_field_or_none)
        c.default = None  # Reset the default argument before wrapping.
        coalesce = Coalesce(c, default, output_field=c._output_field_or_none)
        coalesce.is_summary = c.is_summary
        return coalesce

django.db.models.expressions.Func

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.

    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

django.db.models.expressions.BaseExpression

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.

    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

def reverse_ordering(self)

django.db.models.expressions.BaseExpression

    def reverse_ordering(self):
        return self

def select_format(self, compiler, sql, params)

django.db.models.expressions.BaseExpression

Custom format for select clauses. For example, EXISTS expressions need
to be wrapped in CASE WHEN on Oracle.

    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

def set_source_expressions(self, exprs)

django.db.models.aggregates.Aggregate

    def set_source_expressions(self, exprs):
        self.filter = self.filter and exprs.pop()
        return super().set_source_expressions(exprs)

django.db.models.expressions.Func

    def set_source_expressions(self, exprs):
        self.source_expressions = exprs

django.db.models.expressions.BaseExpression

    def set_source_expressions(self, exprs):
        assert not exprs