Class Ref

django.db.models.expressions.Ref

Reference to column alias of the query. For example, Ref('sum_cost') in qs.annotate(sum_cost=Sum('cost')) query.

Declaration

class Ref(Expression)

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Documentation

Methods

▶ def __init__(self, refs, source) override
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This method overrides django.db.models.expressions.BaseExpression.__init__.
▷ def __repr__(self)
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▶ def as_sql(self, compiler, connection) override

inherited doc Responsible for returning a (sql, [params]) tuple to be included in the current query.

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This method overrides django.db.models.expressions.BaseExpression.as_sql.

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 get_group_by_cols(self, alias=None) override
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This method overrides django.db.models.expressions.BaseExpression.get_group_by_cols.
▶ def get_source_expressions(self) override
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This method overrides django.db.models.expressions.BaseExpression.get_source_expressions.
▶ def relabeled_clone(self, relabels) override
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This method overrides django.db.models.expressions.BaseExpression.relabeled_clone.

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

inherited doc Provide the chance to do any preprocessing or validation before being added to the query.

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This method overrides django.db.models.expressions.BaseExpression.resolve_expression.

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 set_source_expressions(self, exprs) override
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This method overrides django.db.models.expressions.BaseExpression.set_source_expressions.

Inherited methods

Methods inherited from django.db.models.expressions.BaseExpression:
__eq__, __getstate__, __hash__, asc, conditional, contains_aggregate, contains_column_references, contains_over_clause, convert_value, copy, desc, field, flatten, get_db_converters, get_lookup, get_source_fields, get_transform, identity, output_field, reverse_ordering, select_format
Methods inherited from django.db.models.expressions.Combinable:
__add__, __and__, __mod__, __mul__, __neg__, __or__, __pow__, __radd__, __rand__, __rmod__, __rmul__, __ror__, __rpow__, __rsub__, __rtruediv__, __sub__, __truediv__, bitand, bitleftshift, bitor, bitrightshift, bitxor

Reexports

Imported in django.db.models.query.
Imported in django.db.models.sql.query.
Imported in django.db.models.sql.compiler.

Django

Class Ref

Declaration

Documentation

Methods

Inherited methods

Reexports