- union(), intersect(), except() and other "compound" types

of statements have more consistent behavior w.r.t.
parenthesizing.   Each compound element embedded within
another will now be grouped with parenthesis - previously,
the first compound element in the list would not be grouped,
as SQLite doesn't like a statement to start with
parenthesis.   However, Postgresql in particular has
precedence rules regarding INTERSECT, and it is
more consistent for parenthesis to be applied equally
to all sub-elements.   So now, the workaround for SQLite
is also what the workaround for PG was previously -
when nesting compound elements, the first one usually needs
".alias().select()" called on it to wrap it inside
of a subquery.  [ticket:1665]

1 files changed, 3 insertions, 2 deletions

diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index 6db655832..e168a5465 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -268,8 +268,9 @@ class DefaultExecutionContext(base.ExecutionContext):
             self.isinsert = compiled.isinsert
             self.isupdate = compiled.isupdate
             self.isdelete = compiled.isdelete
-            self.execution_options =\
-                    compiled.statement._execution_options.union(self.execution_options)
+            if compiled.statement._execution_options:
+                self.execution_options =\
+                        compiled.statement._execution_options.union(self.execution_options)
 
             if not parameters:
                 self.compiled_parameters = [compiled.construct_params()]