An overhaul of expression handling for special symbols particularly

with conjunctions, e.g.
``None`` :func:`.expression.null` :func:`.expression.true`
:func:`.expression.false`, including consistency in rendering NULL
in conjunctions, "short-circuiting" of :func:`.and_` and :func:`.or_`
expressions which contain boolean constants, and rendering of
boolean constants and expressions as compared to "1" or "0" for backends
that don't feature ``true``/``false`` constants. [ticket:2804]

2 files changed, 4 insertions, 3 deletions

diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index 17fb32663..3df12c0a7 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -2865,8 +2865,9 @@ class Query(object):
                 if adapter:
                     single_crit = adapter.traverse(single_crit)
                 single_crit = self._adapt_clause(single_crit, False, False)
-                context.whereclause = sql.and_(context.whereclause,
-                                            single_crit)
+                context.whereclause = sql.and_(
+                                    sql.True_._ifnone(context.whereclause),
+                                    single_crit)
 
     def __str__(self):
         return str(self._compile_context().statement)
diff --git a/lib/sqlalchemy/orm/relationships.py b/lib/sqlalchemy/orm/relationships.py
index 9fc67cd38..f0b23111c 100644
--- a/lib/sqlalchemy/orm/relationships.py
+++ b/lib/sqlalchemy/orm/relationships.py
@@ -900,7 +900,7 @@ class RelationshipProperty(StrategizedProperty):
                 criterion = criterion._annotate(
                     {'no_replacement_traverse': True})
 
-            crit = j & criterion
+            crit = j & sql.True_._ifnone(criterion)
 
             ex = sql.exists([1], crit, from_obj=dest).correlate_except(dest)
             if secondary is not None: