Fix adaption in AnnotatedLabel; repair needless expense in coercion

Fixed regression involving clause adaption of labeled ORM compound
elements, such as single-table inheritance discriminator expressions with
conditionals or CASE expressions, which could cause aliased expressions
such as those used in ORM join / joinedload operations to not be adapted
correctly, such as referring to the wrong table in the ON clause in a join.

This change also improves a performance bump that was located within the
process of invoking :meth:`_sql.Select.join` given an ORM attribute
as a target.

Fixes: #6550
Change-Id: I98906476f0cce6f41ea00b77c789baa818e9d167

1 files changed, 16 insertions, 0 deletions

diff --git a/test/aaa_profiling/test_orm.py b/test/aaa_profiling/test_orm.py
index 8116e5f21..356ea252d 100644
--- a/test/aaa_profiling/test_orm.py
+++ b/test/aaa_profiling/test_orm.py
@@ -2,6 +2,7 @@ from sqlalchemy import and_
 from sqlalchemy import ForeignKey
 from sqlalchemy import Integer
 from sqlalchemy import join
+from sqlalchemy import select
 from sqlalchemy import String
 from sqlalchemy import testing
 from sqlalchemy.orm import aliased
@@ -966,6 +967,21 @@ class JoinConditionTest(NoCache, fixtures.DeclarativeMappedTest):
 
         go()
 
+    def test_a_to_b_aliased_select_join(self):
+        A, B = self.classes("A", "B")
+
+        b1 = aliased(B)
+
+        stmt = select(A)
+
+        @profiling.function_call_count(times=50, warmup=1)
+        def go():
+            # should not do any adaption or aliasing, this is just getting
+            # the args.  See #6550 where we also fixed this.
+            stmt.join(A.b.of_type(b1))
+
+        go()
+
     def test_a_to_d(self):
         A, D = self.classes("A", "D")