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, 118 insertions, 0 deletions

diff --git a/common/session/custom/session.txx b/common/session/custom/session.txx
new file mode 100644
index 0000000..203b4e3
--- /dev/null
+++ b/common/session/custom/session.txx
@@ -0,0 +1,118 @@
+// file      : common/session/custom/session.txx
+// copyright : Copyright (c) 2009-2012 Code Synthesis Tools CC
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+#include <cassert>
+
+template <typename T>
+typename session::position<T> session::
+insert (odb::database&,
+        const typename odb::object_traits<T>::id_type& id,
+        const typename odb::object_traits<T>::pointer_type& obj)
+{
+  typedef odb::object_traits<T> object_traits;
+
+  std::shared_ptr<object_map_base>& pm (map_[&typeid (T)]);
+
+  if (!pm)
+    pm.reset (new object_map<T>);
+
+  object_map<T>& m (static_cast<object_map<T>&> (*pm));
+
+  typename object_map<T>::value_type vt (id, object_state<T> (obj));
+  std::pair<typename object_map<T>::iterator, bool> r (m.insert (vt));
+
+  // We shall never try to re-insert the same object into the cache.
+  //
+  assert (r.second);
+
+  return position<T> (m, r.first);
+}
+
+template <typename T>
+void session::
+initialize (const position<T>& p)
+{
+  typedef typename odb::object_traits<T>::pointer_type pointer_type;
+
+  // Make a copy for change tracking. If our object model had a
+  // polymorphic hierarchy, then we would have had to use a
+  // virtual function-based mechanism (e.g., clone()) instead of
+  // the copy constructor since for a polymorphic hierarchy all
+  // the derived objects are stored as pointers to the root object.
+  //
+  p.pos_->second.orig = pointer_type (new T (*p.pos_->second.obj));
+}
+
+template <typename T>
+typename odb::object_traits<T>::pointer_type session::
+find (odb::database&, const typename odb::object_traits<T>::id_type& id) const
+{
+  typedef typename odb::object_traits<T>::pointer_type pointer_type;
+
+  type_map::const_iterator ti (map_.find (&typeid (T)));
+
+  if (ti == map_.end ())
+    return pointer_type ();
+
+  const object_map<T>& m (static_cast<const object_map<T>&> (*ti->second));
+  typename object_map<T>::const_iterator oi (m.find (id));
+
+  if (oi == m.end ())
+    return pointer_type ();
+
+  return oi->second.obj;
+}
+
+template <typename T>
+void session::
+erase (odb::database&, const typename odb::object_traits<T>::id_type& id)
+{
+  type_map::iterator ti (map_.find (&typeid (T)));
+
+  if (ti == map_.end ())
+    return;
+
+  object_map<T>& m (static_cast<object_map<T>&> (*ti->second));
+  typename object_map<T>::iterator oi (m.find (id));
+
+  if (oi == m.end ())
+    return;
+
+  m.erase (oi);
+
+  if (m.empty ())
+    map_.erase (ti);
+}
+
+template <typename T>
+void session::object_map<T>::
+flush (odb::database& db)
+{
+  for (typename object_map<T>::iterator i (this->begin ()), e (this->end ());
+       i != e; ++i)
+  {
+    const T& obj (*i->second.obj);
+
+    if (obj.changed (*i->second.orig))
+    {
+      db.update (obj);
+      i->second.flushed_ = true;
+    }
+  }
+}
+
+template <typename T>
+void session::object_map<T>::
+mark ()
+{
+  for (typename object_map<T>::iterator i (this->begin ()), e (this->end ());
+       i != e; ++i)
+  {
+    if (i->second.flushed_)
+    {
+      i->second.orig.reset (new T (*i->second.obj));
+      i->second.flushed_ = false;
+    }
+  }
+}