Implement two-phase session insertion

On the first step an uninitialized object is inserted into the cache
as before (this is necessary to handle recursive loading). The second
step is to notify the session that the object has been initialized.
On this second step the session can perform change tracking preparations,
such as make a copy of the object or reset the modification flag.

New test: common/session/custom (implements a custom session that uses
copies to track changes).

1 files changed, 14 insertions, 1 deletions

diff --git a/odb/cache-traits.hxx b/odb/cache-traits.hxx
index 13363da..5732cfc 100644
--- a/odb/cache-traits.hxx
+++ b/odb/cache-traits.hxx
@@ -77,6 +77,13 @@ namespace odb
         return position_type ();
     }
 
+    static void
+    initialize (const position_type& p)
+    {
+      if (!p.empty_)
+        session_type::template initialize<object_type> (p.pos_);
+    }
+
     static position_type
     insert (odb::database& db, const pointer_type& p)
     {
@@ -107,7 +114,7 @@ namespace odb
     erase (const position_type& p)
     {
       if (!p.empty_)
-        session_type::current ().template erase<object_type> (p.pos_);
+        session_type::template erase<object_type> (p.pos_);
     }
   };
 
@@ -154,6 +161,12 @@ namespace odb
       pointer_type p (&obj);
       return pointer_traits::insert (db, p);
     }
+
+    static void
+    initialize (const position_type& p)
+    {
+      pointer_traits::initialize (p);
+    }
   };
 
   template <typename T, typename S>