[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 04518e310d.

Backport of 278881e376 from main

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,

tests/ordering/tests.py

@@ -8,6 +8,7 @@ from django.db.models import (
     DateTimeField,
     F,
     Max,
+    OrderBy,
     OuterRef,
     Subquery,
     Value,
@@ -619,3 +620,21 @@ class OrderingTests(TestCase):
             ),
             Author.objects.order_by(Length(Upper("name"))),
         )
+
+    def test_ordering_select_related_collision(self):
+        self.assertEqual(
+            Article.objects.select_related("author")
+            .annotate(name=Upper("author__name"))
+            .filter(pk=self.a1.pk)
+            .order_by(OrderBy(F("name")))
+            .first(),
+            self.a1,
+        )
+        self.assertEqual(
+            Article.objects.select_related("author")
+            .annotate(name=Upper("author__name"))
+            .filter(pk=self.a1.pk)
+            .order_by("name")
+            .first(),
+            self.a1,
+        )

tests/postgres_tests/test_array.py

@@ -465,10 +465,9 @@ class TestQuerying(PostgreSQLTestCase):
                     {"field__0": 20, "arrayagg": [self.objs[3].pk]},
                 ],
             )
-        alias = connection.ops.quote_name("field__0")
         sql = ctx[0]["sql"]
         self.assertIn("GROUP BY 1", sql)
-        self.assertIn(f"ORDER BY {alias}", sql)
+        self.assertIn("ORDER BY 1", sql)
 
     def test_index(self):
         self.assertSequenceEqual(