don't fail if purge recyclebin fails/mutex on registry

the recyclebin purge is failing after SetInputSizesTest
on occasion.  try to reduce transaction overhead and don't
error out if the purge fails.

ensure _CONFIGURE_MUTEX is used when mutating or
iterating the _mapper_registries collection.

Change-Id: I9d9cd53b92419a2ad97bae5ee8bdd2657b6e408f

4 files changed, 14 insertions, 11 deletions

diff --git a/lib/sqlalchemy/dialects/oracle/provision.py b/lib/sqlalchemy/dialects/oracle/provision.py
index e0dadd58e..0a2c41009 100644
--- a/lib/sqlalchemy/dialects/oracle/provision.py
+++ b/lib/sqlalchemy/dialects/oracle/provision.py
@@ -60,10 +60,13 @@ def _oracle_drop_db(cfg, eng, ident):
 @stop_test_class_outside_fixtures.for_db("oracle")
 def stop_test_class_outside_fixtures(config, db, cls):
 
-    with db.begin() as conn:
-        # run magic command to get rid of identity sequences
-        # https://floo.bar/2019/11/29/drop-the-underlying-sequence-of-an-identity-column/  # noqa E501
-        conn.exec_driver_sql("purge recyclebin")
+    try:
+        with db.begin() as conn:
+            # run magic command to get rid of identity sequences
+            # https://floo.bar/2019/11/29/drop-the-underlying-sequence-of-an-identity-column/  # noqa E501
+            conn.exec_driver_sql("purge recyclebin")
+    except exc.DatabaseError as err:
+        log.warning("purge recyclebin command failed: %s", err)
 
     # clear statement cache on all connections that were used
     # https://github.com/oracle/python-cx_Oracle/issues/519
diff --git a/lib/sqlalchemy/orm/__init__.py b/lib/sqlalchemy/orm/__init__.py
index ffbe78503..4793fc638 100644
--- a/lib/sqlalchemy/orm/__init__.py
+++ b/lib/sqlalchemy/orm/__init__.py
@@ -268,9 +268,7 @@ def clear_mappers():
 
     """
 
-    with mapperlib._CONFIGURE_MUTEX:
-        all_regs = mapperlib._all_registries()
-        mapperlib._dispose_registries(all_regs, False)
+    mapperlib._dispose_registries(mapperlib._all_registries(), False)
 
 
 joinedload = strategy_options.joinedload._unbound_fn
diff --git a/lib/sqlalchemy/orm/decl_api.py b/lib/sqlalchemy/orm/decl_api.py
index e6d41083f..8afdb3a50 100644
--- a/lib/sqlalchemy/orm/decl_api.py
+++ b/lib/sqlalchemy/orm/decl_api.py
@@ -469,7 +469,8 @@ class registry(object):
 
         self._new_mappers = False
 
-        mapperlib._mapper_registries[self] = True
+        with mapperlib._CONFIGURE_MUTEX:
+            mapperlib._mapper_registries[self] = True
 
     @property
     def mappers(self):
diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 66c062724..16a2c6416 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -62,11 +62,12 @@ _legacy_registry = None
 
 
 def _all_registries():
-    return set(_mapper_registries)
+    with _CONFIGURE_MUTEX:
+        return set(_mapper_registries)
 
 
 def _unconfigured_mappers():
-    for reg in _mapper_registries:
+    for reg in _all_registries():
         for mapper in reg._mappers_to_configure():
             yield mapper
 
@@ -3347,7 +3348,7 @@ def configure_mappers():
 
     """
 
-    _configure_registries(set(_mapper_registries), cascade=True)
+    _configure_registries(_all_registries(), cascade=True)
 
 
 def _configure_registries(registries, cascade):