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Refs #33304 -- Enclosed aggregate ordering logic in an expression.
This greatly simplifies the implementation of contrib.postgres' OrderableAggMixin and allows for reuse in Window expressions.
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Original file line number | Diff line number | Diff line change |
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@@ -1,48 +1,27 @@ | ||
from django.db.models import F, OrderBy | ||
from django.db.models.expressions import OrderByList | ||
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class OrderableAggMixin: | ||
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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 | ||
) | ||
if isinstance(ordering, (list, tuple)): | ||
self.order_by = OrderByList(*ordering) | ||
else: | ||
self.order_by = OrderByList(ordering) | ||
super().__init__(*expressions, **extra) | ||
self.ordering = self._parse_expressions(*ordering) | ||
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def resolve_expression(self, *args, **kwargs): | ||
self.ordering = [expr.resolve_expression(*args, **kwargs) for expr in self.ordering] | ||
self.order_by = self.order_by.resolve_expression(*args, **kwargs) | ||
return super().resolve_expression(*args, **kwargs) | ||
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def as_sql(self, compiler, connection): | ||
if self.ordering: | ||
ordering_params = [] | ||
ordering_expr_sql = [] | ||
for expr in self.ordering: | ||
expr_sql, expr_params = compiler.compile(expr) | ||
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 get_source_expressions(self): | ||
return super().get_source_expressions() + [self.order_by] | ||
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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()]) | ||
*exprs, self.order_by = exprs | ||
return super().set_source_expressions(exprs) | ||
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def get_source_expressions(self): | ||
return super().get_source_expressions() + self.ordering | ||
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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) | ||
def as_sql(self, compiler, connection): | ||
order_by_sql, order_by_params = compiler.compile(self.order_by) | ||
sql, sql_params = super().as_sql(compiler, connection, ordering=order_by_sql) | ||
return sql, (*sql_params, *order_by_params) |
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