Add session, database operations on pointers and const objects

Currently, session is just an object cache. The persist, update, and
erase database operations are overloaded to also work on object
pointers. All the database operations and the query facility now
support const objects.

New session-related exceptions: not_in_session, already_in_session,
const_object.

1 files changed, 18 insertions, 0 deletions

diff --git a/odb/exceptions.cxx b/odb/exceptions.cxx
index c480125..a41f719 100644
--- a/odb/exceptions.cxx
+++ b/odb/exceptions.cxx
@@ -25,6 +25,24 @@ namespace odb
     return "transaction already committed or rolled back";
   }
 
+  const char* already_in_session::
+  what () const throw ()
+  {
+    return "session already in effect in this thread";
+  }
+
+  const char* not_in_session::
+  what () const throw ()
+  {
+    return "session not in effect in this thread";
+  }
+
+  const char* const_object::
+  what () const throw ()
+  {
+    return "object cached in session is const";
+  }
+
   const char* deadlock::
   what () const throw ()
   {