Mark queries as read-only to avoid lock contention

xbob/db/replay/query.py

@@ -136,19 +136,19 @@ class Database(object):
 
     # real-accesses are simpler to query
     if 'enroll' in cls:
-      q = self.session.query(RealAccess).join(File).join(Client).filter(Client.set.in_(groups)).filter(RealAccess.purpose=='enroll').filter(File.light.in_(light)).order_by(Client.id)
+      q = self.session.query(RealAccess).with_lockmode('read').join(File).join(Client).filter(Client.set.in_(groups)).filter(RealAccess.purpose=='enroll').filter(File.light.in_(light)).order_by(Client.id)
       for key, value in [(k.file.id, k.file.path) for k in q]: 
         retval[key] = make_path(str(value), directory, extension)
       
     # real-accesses are simpler to query
     if 'real' in cls:
-      q = self.session.query(RealAccess).join(File).join(Client).filter(RealAccess.protocols.contains(protocol)).filter(Client.set.in_(groups)).filter(File.light.in_(light)).order_by(Client.id)
+      q = self.session.query(RealAccess).with_lockmode('read').join(File).join(Client).filter(RealAccess.protocols.contains(protocol)).filter(Client.set.in_(groups)).filter(File.light.in_(light)).order_by(Client.id)
       for key, value in [(k.file.id, k.file.path) for k in q]:
         retval[key] = make_path(str(value), directory, extension)
 
     # attacks will have to be filtered a little bit more
     if 'attack' in cls:
-      q = self.session.query(Attack).join(File).join(Client).filter(Attack.protocols.contains(protocol)).filter(Client.set.in_(groups)).filter(Attack.attack_support.in_(support)).filter(File.light.in_(light)).order_by(Client.id)
+      q = self.session.query(Attack).with_lockmode('read').join(File).join(Client).filter(Attack.protocols.contains(protocol)).filter(Client.set.in_(groups)).filter(Attack.attack_support.in_(support)).filter(File.light.in_(light)).order_by(Client.id)
 
       for key, value in [(k.file.id, k.file.path) for k in q]: 
         retval[key] = make_path(str(value), directory, extension)
@@ -161,7 +161,7 @@ class Database(object):
     if not self.is_valid():
       raise RuntimeError, "Database '%s' cannot be found at expected location '%s'. Create it and then try re-connecting using Database.connect()" % (INFO.name(), SQLITE_FILE)
 
-    return tuple([k.name for k in self.session.query(Protocol)])
+    return tuple([k.name for k in self.session.query(Protocol).with_lockmode('read')])
 
   def has_protocol(self, name):
     """Tells if a certain protocol is available"""
@@ -169,7 +169,7 @@ class Database(object):
     if not self.is_valid():
       raise RuntimeError, "Database '%s' cannot be found at expected location '%s'. Create it and then try re-connecting using Database.connect()" % (INFO.name(), SQLITE_FILE)
 
-    return self.session.query(Protocol).filter(Protocol.name==name).count() != 0
+    return self.session.query(Protocol).with_lockmode('read').filter(Protocol.name==name).count() != 0
 
   def protocol(self, name):
     """Returns the protocol object in the database given a certain name. Raises
@@ -178,7 +178,7 @@ class Database(object):
     if not self.is_valid():
       raise RuntimeError, "Database '%s' cannot be found at expected location '%s'. Create it and then try re-connecting using Database.connect()" % (INFO.name(), SQLITE_FILE)
 
-    return self.session.query(Protocol).filter(Protocol.name==name).one()
+    return self.session.query(Protocol).with_lockmode('read').filter(Protocol.name==name).one()
 
   def groups(self):
     """Returns the names of all registered groups"""
@@ -228,7 +228,7 @@ class Database(object):
     if not self.is_valid():
       raise RuntimeError, "Database '%s' cannot be found at expected location '%s'. Create it and then try re-connecting using Database.connect()" % (INFO.name(), SQLITE_FILE)
 
-    fobj = self.session.query(File).filter(File.id.in_(ids))
+    fobj = self.session.query(File).with_lockmode('read').filter(File.id.in_(ids))
     retval = []
     for p in ids:
       retval.extend([os.path.join(prefix, str(k.path) + suffix) 
@@ -250,7 +250,7 @@ class Database(object):
     if not self.is_valid():
       raise RuntimeError, "Database '%s' cannot be found at expected location '%s'. Create it and then try re-connecting using Database.connect()" % (INFO.name(), SQLITE_FILE)
 
-    fobj = self.session.query(File).filter(File.path.in_(paths))
+    fobj = self.session.query(File).with_lockmode('read').filter(File.path.in_(paths))
     retval = []
     for p in paths:
       retval.extend([k.id for k in fobj if k.path == p])
@@ -284,7 +284,7 @@ class Database(object):
 
     from bob.io import save
 
-    fobj = self.session.query(File).filter_by(id=id).one()
+    fobj = self.session.query(File).with_lockmode('read').filter_by(id=id).one()
     fullpath = os.path.join(directory, str(fobj.path) + extension)
     fulldir = os.path.dirname(fullpath)
     utils.makedirs_safe(fulldir)