| 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748 |
- from django.db.models.expressions import F, OrderBy
- class OrderableAggMixin:
- def __init__(self, *expressions, ordering=(), **extra):
- if not isinstance(ordering, (list, tuple)):
- ordering = [ordering]
- ordering = ordering or []
- # Transform minus sign prefixed strings into an OrderBy() expression.
- ordering = (
- (OrderBy(F(o[1:]), descending=True) if isinstance(o, str) and o[0] == '-' else o)
- for o in ordering
- )
- super().__init__(*expressions, **extra)
- self.ordering = self._parse_expressions(*ordering)
- def resolve_expression(self, *args, **kwargs):
- self.ordering = [expr.resolve_expression(*args, **kwargs) for expr in self.ordering]
- return super().resolve_expression(*args, **kwargs)
- def as_sql(self, compiler, connection):
- if self.ordering:
- ordering_params = []
- ordering_expr_sql = []
- for expr in self.ordering:
- expr_sql, expr_params = expr.as_sql(compiler, connection)
- ordering_expr_sql.append(expr_sql)
- ordering_params.extend(expr_params)
- sql, sql_params = super().as_sql(compiler, connection, ordering=(
- 'ORDER BY ' + ', '.join(ordering_expr_sql)
- ))
- return sql, sql_params + ordering_params
- return super().as_sql(compiler, connection, ordering='')
- def set_source_expressions(self, exprs):
- # Extract the ordering expressions because ORDER BY clause is handled
- # in a custom way.
- self.ordering = exprs[self._get_ordering_expressions_index():]
- return super().set_source_expressions(exprs[:self._get_ordering_expressions_index()])
- def get_source_expressions(self):
- return super().get_source_expressions() + self.ordering
- def _get_ordering_expressions_index(self):
- """Return the index at which the ordering expressions start."""
- source_expressions = self.get_source_expressions()
- return len(source_expressions) - len(self.ordering)
|
