- More fixes to SQLite "join rewriting"; the fix from :ticket:`2967`

implemented right before the release of 0.9.3 affected the case where
a UNION contained nested joins in it.   "Join rewriting" is a feature
with a wide range of possibilities and is the first intricate
"SQL rewriting" feature we've introduced in years, so we're sort of
going through a lot of iterations with it (not unlike eager loading
back in the 0.2/0.3 series, polymorphic loading in 0.4/0.5). We should
be there soon so thanks for bearing with us :).
fixes #2969   re: #2967
- solve the issue of join rewriting inspecting various types of
from objects without using isinstance(), by adding some new
underscored inspection flags to the FromClause hierarchy.

1 files changed, 11 insertions, 0 deletions

diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py
index bda3d655e..59d6687b5 100644
--- a/lib/sqlalchemy/sql/selectable.py
+++ b/lib/sqlalchemy/sql/selectable.py
@@ -137,6 +137,10 @@ class FromClause(Selectable):
     named_with_column = False
     _hide_froms = []
 
+    _is_join = False
+    _is_select = False
+    _is_from_container = False
+
     _textual = False
     """a marker that allows us to easily distinguish a :class:`.TextAsFrom`
     or similar object from other kinds of :class:`.FromClause` objects."""
@@ -504,6 +508,8 @@ class Join(FromClause):
     """
     __visit_name__ = 'join'
 
+    _is_join = True
+
     def __init__(self, left, right, onclause=None, isouter=False):
         """Construct a new :class:`.Join`.
 
@@ -910,6 +916,8 @@ class Alias(FromClause):
     __visit_name__ = 'alias'
     named_with_column = True
 
+    _is_from_container = True
+
     def __init__(self, selectable, name=None):
         baseselectable = selectable
         while isinstance(baseselectable, Alias):
@@ -1716,6 +1724,8 @@ class CompoundSelect(GenerativeSelect):
     INTERSECT = util.symbol('INTERSECT')
     INTERSECT_ALL = util.symbol('INTERSECT ALL')
 
+    _is_from_container = True
+
     def __init__(self, keyword, *selects, **kwargs):
         self._auto_correlate = kwargs.pop('correlate', False)
         self.keyword = keyword
@@ -1982,6 +1992,7 @@ class Select(HasPrefixes, GenerativeSelect):
     _correlate = ()
     _correlate_except = None
     _memoized_property = SelectBase._memoized_property
+    _is_select = True
 
     def __init__(self,
                 columns=None,