- Some changes to how the :attr:`.FromClause.c` collection behaves

when presented with duplicate columns.  The behavior of emitting a
warning and replacing the old column with the same name still
remains to some degree; the replacement in particular is to maintain
backwards compatibility.  However, the replaced column still remains
associated with the ``c`` collection now in a collection ``._all_columns``,
which is used by constructs such as aliases and unions, to deal with
the set of columns in ``c`` more towards what is actually in the
list of columns rather than the unique set of key names.  This helps
with situations where SELECT statements with same-named columns
are used in unions and such, so that the union can match the columns
up positionally and also there's some chance of :meth:`.FromClause.corresponding_column`
still being usable here (it can now return a column that is only
in selectable.c._all_columns and not otherwise named).
The new collection is underscored as we still need to decide where this
list might end up.   Theoretically it
would become the result of iter(selectable.c), however this would mean
that the length of the iteration would no longer match the length of
keys(), and that behavior needs to be checked out.
fixes #2974
- add a bunch more tests for ColumnCollection

1 files changed, 35 insertions, 0 deletions

diff --git a/test/sql/test_selectable.py b/test/sql/test_selectable.py
index 9617cfdf7..5d3d53b88 100644
--- a/test/sql/test_selectable.py
+++ b/test/sql/test_selectable.py
@@ -413,6 +413,41 @@ class SelectableTest(fixtures.TestBase, AssertsExecutionResults, AssertsCompiled
         assert u2.corresponding_column(s1.c.col1) is u2.c.col1
         assert u2.corresponding_column(s2.c.col1) is u2.c.col1
 
+    @testing.emits_warning("Column 'col1'")
+    def test_union_dupe_keys(self):
+        s1 = select([table1.c.col1, table1.c.col2, table2.c.col1])
+        s2 = select([table2.c.col1, table2.c.col2, table2.c.col3])
+        u1 = union(s1, s2)
+
+        assert u1.corresponding_column(s1.c._all_columns[0]) is u1.c._all_columns[0]
+        assert u1.corresponding_column(s2.c.col1) is u1.c._all_columns[0]
+        assert u1.corresponding_column(s1.c.col2) is u1.c.col2
+        assert u1.corresponding_column(s2.c.col2) is u1.c.col2
+
+        assert u1.corresponding_column(s2.c.col3) is u1.c._all_columns[2]
+
+        assert u1.corresponding_column(table2.c.col1) is u1.c._all_columns[2]
+        assert u1.corresponding_column(table2.c.col3) is u1.c._all_columns[2]
+
+    @testing.emits_warning("Column 'col1'")
+    def test_union_alias_dupe_keys(self):
+        s1 = select([table1.c.col1, table1.c.col2, table2.c.col1]).alias()
+        s2 = select([table2.c.col1, table2.c.col2, table2.c.col3])
+        u1 = union(s1, s2)
+
+        assert u1.corresponding_column(s1.c._all_columns[0]) is u1.c._all_columns[0]
+        assert u1.corresponding_column(s2.c.col1) is u1.c._all_columns[0]
+        assert u1.corresponding_column(s1.c.col2) is u1.c.col2
+        assert u1.corresponding_column(s2.c.col2) is u1.c.col2
+
+        assert u1.corresponding_column(s2.c.col3) is u1.c._all_columns[2]
+
+        # this differs from the non-alias test because table2.c.col1 is
+        # more directly at s2.c.col1 than it is s1.c.col1.
+        assert u1.corresponding_column(table2.c.col1) is u1.c._all_columns[0]
+        assert u1.corresponding_column(table2.c.col3) is u1.c._all_columns[2]
+
+
     def test_select_union(self):
 
         # like testaliasunion, but off a Select off the union.