SelectBase no longer a FromClause

As part of the SQLAlchemy 2.0 migration project, a conceptual change has
been made to the role of the :class:`.SelectBase` class hierarchy,
which is the root of all "SELECT" statement constructs, in that they no
longer serve directly as FROM clauses, that is, they no longer subclass
:class:`.FromClause`.  For end users, the change mostly means that any
placement of a :func:`.select` construct in the FROM clause of another
:func:`.select` requires first that it be wrapped in a subquery first,
which historically is through the use of the :meth:`.SelectBase.alias`
method, and is now also available through the use of
:meth:`.SelectBase.subquery`.    This was usually a requirement in any
case since several databases don't accept unnamed SELECT subqueries
in their FROM clause in any case.

See the documentation in this change for lots more detail.

Fixes: #4617
Change-Id: I0f6174ee24b9a1a4529168e52e855e12abd60667

1 files changed, 5 insertions, 5 deletions

diff --git a/test/sql/test_metadata.py b/test/sql/test_metadata.py
index 0d3a04430..5081cfbd2 100644
--- a/test/sql/test_metadata.py
+++ b/test/sql/test_metadata.py
@@ -2634,7 +2634,7 @@ class ConstraintTest(fixtures.TestBase):
 
     def test_column_references_derived(self):
         t1, t2, t3 = self._single_fixture()
-        s1 = tsa.select([tsa.select([t1]).alias()])
+        s1 = tsa.select([tsa.select([t1]).alias()]).subquery()
         assert t2.c.a.references(s1.c.a)
         assert not t2.c.a.references(s1.c.b)
 
@@ -2646,7 +2646,7 @@ class ConstraintTest(fixtures.TestBase):
 
     def test_derived_column_references(self):
         t1, t2, t3 = self._single_fixture()
-        s1 = tsa.select([tsa.select([t2]).alias()])
+        s1 = tsa.select([tsa.select([t2]).alias()]).subquery()
         assert s1.c.a.references(t1.c.a)
         assert not s1.c.a.references(t1.c.b)
 
@@ -2765,7 +2765,7 @@ class ConstraintTest(fixtures.TestBase):
             Column("id", Integer, ForeignKey("t1.id"), primary_key=True),
         )
 
-        s = tsa.select([t2])
+        s = tsa.select([t2]).subquery()
         t2fk = list(t2.c.id.foreign_keys)[0]
         sfk = list(s.c.id.foreign_keys)[0]
 
@@ -3532,7 +3532,7 @@ class ColumnDefinitionTest(AssertsCompiledSQL, fixtures.TestBase):
         s = select([t1.select().alias()])
 
         # proxy has goofy thing
-        eq_(s.c.name.my_goofy_thing(), "hi")
+        eq_(s.subquery().c.name.my_goofy_thing(), "hi")
 
         # compile works
         self.assert_compile(
@@ -3561,7 +3561,7 @@ class ColumnDefinitionTest(AssertsCompiledSQL, fixtures.TestBase):
             "'test.sql.test_metadata..*MyColumn'> "
             "object.  Ensure the class includes a _constructor()",
             getattr,
-            select([t1.select().alias()]),
+            select([t1.select().alias()]).subquery(),
             "c",
         )