From 498db831718cb5df213b1afdd2027878e0e72fd4 Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Thu, 18 Feb 2021 10:43:16 -0500
Subject: [PATCH] Extract table names when comparing to nrte error

Fixed issue where the process of joining two tables could fail if one of
the tables had an unrelated, unresolvable foreign key constraint which
would raise :class:`_exc.NoReferenceError` within the join process, which
nonetheless could be bypassed to allow the join to complete. The logic
which tested the exception for signficance within the process would make
assumptions about the construct which would fail.

Fixes: #5952
Change-Id: I492dacd082ddcf8abb1310ed447a6ed734595bb7
---
 doc/build/changelog/unreleased_13/5952.rst | 11 +++++
 lib/sqlalchemy/sql/selectable.py           |  9 +++-
 test/sql/test_selectable.py                | 49 ++++++++++++++++++++++
 3 files changed, 67 insertions(+), 2 deletions(-)
 create mode 100644 doc/build/changelog/unreleased_13/5952.rst

diff --git a/doc/build/changelog/unreleased_13/5952.rst b/doc/build/changelog/unreleased_13/5952.rst
new file mode 100644
index 0000000000..7166e92675
--- /dev/null
+++ b/doc/build/changelog/unreleased_13/5952.rst
@@ -0,0 +1,11 @@
+.. change::
+    :tags: bug, orm
+    :tickets: 5952
+
+    Fixed issue where the process of joining two tables could fail if one of
+    the tables had an unrelated, unresolvable foreign key constraint which
+    would raise :class:`_exc.NoReferenceError` within the join process, which
+    nonetheless could be bypassed to allow the join to complete. The logic
+    which tested the exception for signficance within the process would make
+    assumptions about the construct which would fail.
+
diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py
index ee2c4dafc5..7c53f437c6 100644
--- a/lib/sqlalchemy/sql/selectable.py
+++ b/lib/sqlalchemy/sql/selectable.py
@@ -1229,9 +1229,12 @@ class Join(roles.DMLTableRole, FromClause):
         return bool(constraints)
 
     @classmethod
+    @util.preload_module("sqlalchemy.sql.util")
     def _joincond_scan_left_right(
         cls, a, a_subset, b, consider_as_foreign_keys
     ):
+        sql_util = util.preloaded.sql_util
+
         a = coercions.expect(roles.FromClauseRole, a)
         b = coercions.expect(roles.FromClauseRole, b)
 
@@ -1251,7 +1254,8 @@ class Join(roles.DMLTableRole, FromClause):
                 try:
                     col = fk.get_referent(left)
                 except exc.NoReferenceError as nrte:
-                    if nrte.table_name == left.name:
+                    table_names = {t.name for t in sql_util.find_tables(left)}
+                    if nrte.table_name in table_names:
                         raise
                     else:
                         continue
@@ -1270,7 +1274,8 @@ class Join(roles.DMLTableRole, FromClause):
                     try:
                         col = fk.get_referent(b)
                     except exc.NoReferenceError as nrte:
-                        if nrte.table_name == b.name:
+                        table_names = {t.name for t in sql_util.find_tables(b)}
+                        if nrte.table_name in table_names:
                             raise
                         else:
                             continue
diff --git a/test/sql/test_selectable.py b/test/sql/test_selectable.py
index 9f0c72247c..762146a3d3 100644
--- a/test/sql/test_selectable.py
+++ b/test/sql/test_selectable.py
@@ -1834,6 +1834,55 @@ class JoinConditionTest(fixtures.TestBase, AssertsCompiledSQL):
         assert sql_util.join_condition(t1, t2).compare(t1.c.x == t2.c.id)
         assert sql_util.join_condition(t2, t1).compare(t1.c.x == t2.c.id)
 
+    def test_join_cond_no_such_unrelated_table_dont_compare_names(self):
+        m = MetaData()
+        t1 = Table(
+            "t1",
+            m,
+            Column("y", Integer, ForeignKey("t22.id")),
+            Column("x", Integer, ForeignKey("t2.id")),
+            Column("q", Integer, ForeignKey("t22.id")),
+        )
+        t2 = Table(
+            "t2",
+            m,
+            Column("id", Integer),
+            Column("t3id", ForeignKey("t3.id")),
+            Column("z", ForeignKey("t33.id")),
+        )
+        t3 = Table(
+            "t3", m, Column("id", Integer), Column("q", ForeignKey("t4.id"))
+        )
+
+        j1 = t1.join(t2)
+
+        assert sql_util.join_condition(j1, t3).compare(t2.c.t3id == t3.c.id)
+
+    def test_join_cond_no_such_unrelated_column_dont_compare_names(self):
+        m = MetaData()
+        t1 = Table(
+            "t1",
+            m,
+            Column("x", Integer, ForeignKey("t2.id")),
+        )
+        t2 = Table(
+            "t2",
+            m,
+            Column("id", Integer),
+            Column("t3id", ForeignKey("t3.id")),
+            Column("q", ForeignKey("t5.q")),
+        )
+        t3 = Table(
+            "t3", m, Column("id", Integer), Column("t4id", ForeignKey("t4.id"))
+        )
+        t4 = Table("t4", m, Column("id", Integer))
+        Table("t5", m, Column("id", Integer))
+        j1 = t1.join(t2)
+
+        j2 = t3.join(t4)
+
+        assert sql_util.join_condition(j1, j2).compare(t2.c.t3id == t3.c.id)
+
     def test_join_cond_no_such_related_table(self):
         m1 = MetaData()
         m2 = MetaData()
-- 
2.47.2