django.db.models.expressions.BaseExpression

class documentation

class BaseExpression: (source)

Known subclasses: django.db.models.expressions.Expression, django.db.models.expressions.Subquery, django.db.models.sql.query.Query

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Base class for all query expressions.

Method	`__getstate__`	Undocumented
Method	`__init__`	Undocumented
Method	`as_sql`	Responsible for returning a (sql, [params]) tuple to be included in the current query.
Method	`asc`	Undocumented
Method	`copy`	Undocumented
Method	`desc`	Undocumented
Method	`flatten`	Recursively yield this expression and all subexpressions, in depth-first order.
Method	`get_db_converters`	Undocumented
Method	`get_group_by_cols`	Undocumented
Method	`get_lookup`	Undocumented
Method	`get_source_expressions`	Undocumented
Method	`get_source_fields`	Return the underlying field types used by this aggregate.
Method	`get_transform`	Undocumented
Method	`prefix_references`	Undocumented
Method	`relabeled_clone`	Undocumented
Method	`replace_references`	Undocumented
Method	`resolve_expression`	Provide the chance to do any preprocessing or validation before being added to the query.
Method	`reverse_ordering`	Undocumented
Method	`select_format`	Custom format for select clauses. For example, EXISTS expressions need to be wrapped in CASE WHEN on Oracle.
Method	`set_source_expressions`	Undocumented
Class Variable	`filterable`	Undocumented
Class Variable	`is_summary`	Undocumented
Class Variable	`window_compatible`	Undocumented
Property	`conditional`	Undocumented
Property	`contains_aggregate`	Undocumented
Property	`contains_column_references`	Undocumented
Property	`contains_over_clause`	Undocumented
Property	`convert_value`	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.
Property	`field`	Undocumented
Property	`output_field`	Return the output type of this expressions.
Static Method	`_convert_value_noop`	Undocumented
Method	`_parse_expressions`	Undocumented
Method	`_resolve_output_field`	Attempt to infer the output type of the expression.
Class Variable	`_output_field_resolved_to_none`	Undocumented
Property	`_output_field_or_none`	Return the output field of this expression, or None if _resolve_output_field() didn't return an output type.

def __getstate__(self): (source) ¶

Undocumented

def as_sql(self, compiler, connection): (source) ¶

overridden in django.contrib.postgres.fields.ranges.RangeBoundary, django.db.models.expressions.Case, django.db.models.expressions.Col, django.db.models.expressions.CombinedExpression, django.db.models.expressions.ExpressionWrapper, django.db.models.expressions.Func, django.db.models.expressions.OrderBy, django.db.models.expressions.RawSQL, django.db.models.expressions.Ref, django.db.models.expressions.Star, django.db.models.expressions.Subquery, django.db.models.expressions.Value, django.db.models.expressions.When, django.db.models.expressions.Window, django.db.models.expressions.WindowFrame, django.db.models.fields.json.ContainedBy, django.db.models.fields.json.DataContains, django.db.models.fields.json.HasKeyLookup, django.db.models.lookups.BuiltinLookup, django.db.models.lookups.YearLookup, django.db.models.sql.query.Query

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 asc(self, **kwargs): (source) ¶

overridden in django.db.models.expressions.OrderBy

Undocumented

def copy(self): (source) ¶

overridden in django.db.models.expressions.Case, django.db.models.expressions.Func, django.db.models.expressions.Subquery

Undocumented

def desc(self, **kwargs): (source) ¶

overridden in django.db.models.expressions.OrderBy

Undocumented

def flatten(self): (source) ¶

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

def get_db_converters(self, connection): (source) ¶

overridden in django.db.models.expressions.Col

Undocumented

def get_lookup(self, lookup): (source) ¶

Undocumented

def get_source_expressions(self): (source) ¶

overridden in django.db.models.expressions.Case, django.db.models.expressions.CombinedExpression, django.db.models.expressions.ExpressionWrapper, django.db.models.expressions.Func, django.db.models.expressions.OrderBy, django.db.models.expressions.Ref, django.db.models.expressions.Subquery, django.db.models.expressions.When, django.db.models.expressions.Window, django.db.models.expressions.WindowFrame, django.db.models.lookups.Lookup

Undocumented

def get_source_fields(self): (source) ¶

overridden in django.db.models.aggregates.Aggregate, django.db.models.expressions.When

Return the underlying field types used by this aggregate.

def get_transform(self, name): (source) ¶

Undocumented

def prefix_references(self, prefix): (source) ¶

Undocumented

def relabeled_clone(self, change_map): (source) ¶

overridden in django.db.models.expressions.Col, django.db.models.expressions.Ref, django.db.models.sql.query.Query

Undocumented

def replace_references(self, references_map): (source) ¶

Undocumented

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

overridden in django.db.models.expressions.Case, django.db.models.expressions.CombinedExpression, django.db.models.expressions.Func, django.db.models.expressions.RawSQL, django.db.models.expressions.Ref, django.db.models.expressions.Value, django.db.models.expressions.When, django.db.models.lookups.Lookup, django.db.models.sql.query.Query

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 reverse_ordering(self): (source) ¶

overridden in django.db.models.expressions.OrderBy

Undocumented

def select_format(self, compiler, sql, params): (source) ¶

overridden in django.db.models.expressions.Exists, django.db.models.lookups.Lookup

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

def set_source_expressions(self, exprs): (source) ¶

Undocumented

filterable: bool = (source) ¶

overridden in django.db.models.expressions.Window

Undocumented

is_summary: bool = (source) ¶

Undocumented

window_compatible: bool = (source) ¶

overridden in django.db.models.aggregates.Aggregate, django.db.models.functions.window.CumeDist, django.db.models.functions.window.DenseRank, django.db.models.functions.window.FirstValue, django.db.models.functions.window.LagLeadFunction, django.db.models.functions.window.LastValue, django.db.models.functions.window.NthValue, django.db.models.functions.window.Ntile, django.db.models.functions.window.PercentRank, django.db.models.functions.window.Rank, django.db.models.functions.window.RowNumber

Undocumented

@property
conditional = (source) ¶

overridden in django.db.models.expressions.OrderBy, django.db.models.expressions.When

Undocumented

@cached_property
contains_aggregate = (source) ¶

overridden in django.db.models.aggregates.Aggregate, django.db.models.expressions.Subquery, django.db.models.expressions.Window

Undocumented

@cached_property
contains_column_references = (source) ¶

overridden in django.db.models.expressions.Col

Undocumented

@cached_property
contains_over_clause = (source) ¶

overridden in django.db.models.expressions.Window

Undocumented

@cached_property
convert_value = (source) ¶

overridden in django.db.models.functions.datetime.TruncBase

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.

@property
field = (source) ¶

Undocumented

@cached_property
output_field = (source) ¶

overridden in django.contrib.postgres.fields.ranges.IsEmpty, django.contrib.postgres.fields.ranges.LowerInclusive, django.contrib.postgres.fields.ranges.LowerInfinite, django.contrib.postgres.fields.ranges.RangeEndsWith, django.contrib.postgres.fields.ranges.RangeStartsWith, django.contrib.postgres.fields.ranges.UpperInclusive, django.contrib.postgres.fields.ranges.UpperInfinite, django.db.models.aggregates.Count, django.db.models.expressions.Exists, django.db.models.expressions.TemporalSubtraction, django.db.models.functions.Extract, django.db.models.functions.JSONObject, django.db.models.functions.Left, django.db.models.functions.Length, django.db.models.functions.LPad, django.db.models.functions.Now, django.db.models.functions.Ord, django.db.models.functions.Repeat, django.db.models.functions.StrIndex, django.db.models.functions.Substr, django.db.models.functions.TruncDate, django.db.models.functions.TruncTime, django.db.models.functions.window.CumeDist, django.db.models.functions.window.DenseRank, django.db.models.functions.window.Ntile, django.db.models.functions.window.PercentRank, django.db.models.functions.window.Rank, django.db.models.functions.window.RowNumber, django.db.models.lookups.Lookup, django.db.models.sql.query.Query

Return the output type of this expressions.

@staticmethod
def _convert_value_noop(value, expression, connection): (source) ¶

Undocumented

def _parse_expressions(self, *expressions): (source) ¶

Undocumented

def _resolve_output_field(self): (source) ¶

overridden in django.db.models.expressions.CombinedExpression, django.db.models.expressions.Subquery, django.db.models.expressions.Value, django.db.models.expressions.Window, django.db.models.functions.Round, django.db.models.functions.window.LagLeadFunction, django.db.models.functions.window.NthValue

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.

_output_field_resolved_to_none: bool = (source) ¶

Undocumented

@cached_property
_output_field_or_none = (source) ¶

Return the output field of this expression, or None if _resolve_output_field() didn't return an output type.