Only use schema_translate_map on SchemaItem subclasses

Fixed bug in new "schema translate" feature where the translated schema
name would be invoked in terms of an alias name when rendered along
with a column expression; occurred only when the source translate
name was "None".   The "schema translate" feature now only takes
effect for :class:`.SchemaItem` and :class:`.SchemaType` subclasses,
that is, objects that correspond to a DDL-creatable structure in
a database.

Change-Id: Ie8cb35aeaba2c67efec8c8c57c219e4dd346e44a
Fixes: #3924

5 files changed, 68 insertions, 2 deletions

diff --git a/doc/build/changelog/changelog_11.rst b/doc/build/changelog/changelog_11.rst
index 645020c42..ffb4bce94 100644
--- a/doc/build/changelog/changelog_11.rst
+++ b/doc/build/changelog/changelog_11.rst
@@ -21,6 +21,18 @@
 .. changelog::
     :version: 1.1.7
 
+    .. change::
+        :tags: bug, sql
+        :tickets: 3924
+
+        Fixed bug in new "schema translate" feature where the translated schema
+        name would be invoked in terms of an alias name when rendered along
+        with a column expression; occurred only when the source translate
+        name was "None".   The "schema translate" feature now only takes
+        effect for :class:`.SchemaItem` and :class:`.SchemaType` subclasses,
+        that is, objects that correspond to a DDL-creatable structure in
+        a database.
+
 .. changelog::
     :version: 1.1.6
     :released: February 28, 2017
diff --git a/lib/sqlalchemy/sql/schema.py b/lib/sqlalchemy/sql/schema.py
index 9bb0eee43..08f23c4af 100644
--- a/lib/sqlalchemy/sql/schema.py
+++ b/lib/sqlalchemy/sql/schema.py
@@ -114,6 +114,9 @@ class SchemaItem(SchemaEventTarget, visitors.Visitable):
         schema_item.dispatch._update(self.dispatch)
         return schema_item
 
+    def _translate_schema(self, effective_schema, map_):
+        return map_.get(effective_schema, effective_schema)
+
 
 class Table(DialectKWArgs, SchemaItem, TableClause):
     r"""Represent a table in a database.
@@ -3974,7 +3977,8 @@ class _SchemaTranslateMap(object):
         if map_ is not None:
             def schema_for_object(obj):
                 effective_schema = self._default_schema_getter(obj)
-                effective_schema = map_.get(effective_schema, effective_schema)
+                effective_schema = obj._translate_schema(
+                    effective_schema, map_)
                 return effective_schema
             self.__call__ = schema_for_object
             self.hash_key = ";".join(
diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py
index 91a12bd33..b69d667c6 100644
--- a/lib/sqlalchemy/sql/selectable.py
+++ b/lib/sqlalchemy/sql/selectable.py
@@ -351,6 +351,9 @@ class FromClause(Selectable):
 
     """
 
+    def _translate_schema(self, effective_schema, map_):
+        return effective_schema
+
     _memoized_property = util.group_expirable_memoized_property(["_columns"])
 
     @util.deprecated(
diff --git a/lib/sqlalchemy/sql/sqltypes.py b/lib/sqlalchemy/sql/sqltypes.py
index 78a130f62..bb39388ab 100644
--- a/lib/sqlalchemy/sql/sqltypes.py
+++ b/lib/sqlalchemy/sql/sqltypes.py
@@ -997,6 +997,9 @@ class SchemaType(SchemaEventTarget):
                 util.portable_instancemethod(self._on_metadata_drop)
             )
 
+    def _translate_schema(self, effective_schema, map_):
+        return map_.get(effective_schema, effective_schema)
+
     def _set_parent(self, column):
         column._on_table_attach(util.portable_instancemethod(self._set_table))
 
diff --git a/test/sql/test_compiler.py b/test/sql/test_compiler.py
index e7504a748..e65db2a36 100644
--- a/test/sql/test_compiler.py
+++ b/test/sql/test_compiler.py
@@ -3374,6 +3374,12 @@ class SchemaTest(fixtures.TestBase, AssertsCompiledSQL):
                             )
 
     def test_schema_translate_select(self):
+        m = MetaData()
+        table1 = Table(
+            'mytable', m, Column('myid', Integer),
+            Column('name', String),
+            Column('description', String)
+        )
         schema_translate_map = {"remote_owner": "foob", None: 'bar'}
 
         self.assert_compile(
@@ -3402,13 +3408,51 @@ class SchemaTest(fixtures.TestBase, AssertsCompiledSQL):
             "SELECT mytable.myid, mytable.name, mytable.description, "
             "foob.remotetable.rem_id, foob.remotetable.datatype_id, "
             "foob.remotetable.value FROM mytable JOIN foob.remotetable "
-            "ON foob.remotetable.rem_id = mytable.myid",
+            "ON mytable.myid = foob.remotetable.rem_id",
+            schema_translate_map=schema_translate_map
+        )
+
+    def test_schema_translate_aliases(self):
+        schema_translate_map = {None: 'bar'}
+
+        m = MetaData()
+        table1 = Table(
+            'mytable', m, Column('myid', Integer),
+            Column('name', String),
+            Column('description', String)
+        )
+        table2 = Table(
+            'myothertable', m, Column('otherid', Integer),
+            Column('othername', String),
+        )
+
+        alias = table1.alias()
+
+        stmt = select([
+            table2, alias
+        ]).select_from(table2.join(alias, table2.c.otherid == alias.c.myid)).\
+            where(alias.c.name == 'foo')
+
+        self.assert_compile(
+            stmt,
+            "SELECT bar.myothertable.otherid, bar.myothertable.othername, "
+            "mytable_1.myid, mytable_1.name, mytable_1.description "
+            "FROM bar.myothertable JOIN bar.mytable AS mytable_1 "
+            "ON bar.myothertable.otherid = mytable_1.myid "
+            "WHERE mytable_1.name = :name_1",
             schema_translate_map=schema_translate_map
         )
 
     def test_schema_translate_crud(self):
         schema_translate_map = {"remote_owner": "foob", None: 'bar'}
 
+        m = MetaData()
+        table1 = Table(
+            'mytable', m,
+            Column('myid', Integer), Column('name', String),
+            Column('description', String)
+        )
+
         self.assert_compile(
             table1.insert().values(description='foo'),
             "INSERT INTO bar.mytable (description) VALUES (:description)",