- Fixed an assertion that would raise somewhat inappropriately

if a :class:`.Index` were associated with a :class:`.Column` that
is associated with a lower-case-t :class:`.TableClause`; the
association should be ignored for the purposes of associating
the index with a :class:`.Table`.
fixes #3616

1 files changed, 7 insertions, 3 deletions

diff --git a/lib/sqlalchemy/sql/schema.py b/lib/sqlalchemy/sql/schema.py
index 42dbe72b2..b244d746c 100644
--- a/lib/sqlalchemy/sql/schema.py
+++ b/lib/sqlalchemy/sql/schema.py
@@ -2498,9 +2498,13 @@ class ColumnCollectionMixin(object):
             has_string_cols = set(self._pending_colargs).difference(col_objs)
             if not has_string_cols:
                 def _col_attached(column, table):
-                    cols_wo_table.discard(column)
-                    if not cols_wo_table:
-                        self._check_attach(evt=True)
+                    # this isinstance() corresponds with the
+                    # isinstance() above; only want to count Table-bound
+                    # columns
+                    if isinstance(table, Table):
+                        cols_wo_table.discard(column)
+                        if not cols_wo_table:
+                            self._check_attach(evt=True)
                 self._cols_wo_table = cols_wo_table
                 for col in cols_wo_table:
                     col._on_table_attach(_col_attached)