From aab25a69dd09e6717ff86175ff62c29b847a7791 Mon Sep 17 00:00:00 2001
From: Simon Charette <charette.s@gmail.com>
Date: Fri, 17 Feb 2023 20:38:08 -0500
Subject: [4.2.x] Fixed #34346 -- Ordered selected expressions by position.

Used the same approach as for #34176 by using selected expressions
position to prevent ambiguous aliases in collisions.

Thanks henribru for the report.

Regression in 04518e310d4552ff7595a34f5a7f93487d78a406.

Backport of 278881e37619278789942513916acafaa88d26f3 from main
---
 django/db/models/sql/compiler.py | 43 ++++++++++++++++++++++++++++++++--------
 1 file changed, 35 insertions(+), 8 deletions(-)

(limited to 'django/db/models/sql')

diff --git a/django/db/models/sql/compiler.py b/django/db/models/sql/compiler.py
index c07076d54a..348cfa381a 100644
--- a/django/db/models/sql/compiler.py
+++ b/django/db/models/sql/compiler.py
@@ -27,6 +27,15 @@ from django.utils.hashable import make_hashable
 from django.utils.regex_helper import _lazy_re_compile
 
 
+class PositionRef(Ref):
+    def __init__(self, ordinal, refs, source):
+        self.ordinal = ordinal
+        super().__init__(refs, source)
+
+    def as_sql(self, compiler, connection):
+        return str(self.ordinal), ()
+
+
 class SQLCompiler:
     # Multiline ordering SQL clause may appear from RawSQL.
     ordering_parts = _lazy_re_compile(
@@ -321,6 +330,14 @@ class SQLCompiler:
         else:
             default_order, _ = ORDER_DIR["DESC"]
 
+        selected_exprs = {}
+        if select := self.select:
+            for ordinal, (expr, _, alias) in enumerate(select, start=1):
+                pos_expr = PositionRef(ordinal, alias, expr)
+                if alias:
+                    selected_exprs[alias] = pos_expr
+                selected_exprs[expr] = pos_expr
+
         for field in ordering:
             if hasattr(field, "resolve_expression"):
                 if isinstance(field, Value):
@@ -331,13 +348,23 @@ class SQLCompiler:
                 if not self.query.standard_ordering:
                     field = field.copy()
                     field.reverse_ordering()
-                if isinstance(field.expression, F) and (
-                    annotation := self.query.annotation_select.get(
-                        field.expression.name
-                    )
+                select_ref = selected_exprs.get(field.expression)
+                if select_ref or (
+                    isinstance(field.expression, F)
+                    and (select_ref := selected_exprs.get(field.expression.name))
                 ):
-                    field.expression = Ref(field.expression.name, annotation)
-                yield field, isinstance(field.expression, Ref)
+                    # Emulation of NULLS (FIRST|LAST) cannot be combined with
+                    # the usage of ordering by position.
+                    if (
+                        field.nulls_first is None and field.nulls_last is None
+                    ) or self.connection.features.supports_order_by_nulls_modifier:
+                        field.expression = select_ref
+                    # Alias collisions are not possible when dealing with
+                    # combined queries so fallback to it if emulation of NULLS
+                    # handling is required.
+                    elif self.query.combinator:
+                        field.expression = Ref(select_ref.refs, select_ref.source)
+                yield field, select_ref is not None
                 continue
             if field == "?":  # random
                 yield OrderBy(Random()), False
@@ -346,11 +373,11 @@ class SQLCompiler:
             col, order = get_order_dir(field, default_order)
             descending = order == "DESC"
 
-            if col in self.query.annotation_select:
+            if select_ref := selected_exprs.get(col):
                 # Reference to expression in SELECT clause
                 yield (
                     OrderBy(
-                        Ref(col, self.query.annotation_select[col]),
+                        select_ref,
                         descending=descending,
                     ),
                     True,
-- 
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