Add support for recursive object loading

If an object of a type needs to be loaded recursively, then it is addded to
the delayed loading list which is processed once the statements are unlocked.

3 files changed, 44 insertions, 32 deletions

diff --git a/odb/cache-traits.hxx b/odb/cache-traits.hxx
index 5d32624..a475d35 100644
--- a/odb/cache-traits.hxx
+++ b/odb/cache-traits.hxx
@@ -27,12 +27,10 @@ namespace odb
     struct insert_guard
     {
       insert_guard (const position_type& pos): pos_ (pos) {}
+      ~insert_guard () {erase (pos_);}
 
-      ~insert_guard ()
-      {
-        if (pos_.map_ != 0)
-          session::current ().erase<element_type> (pos_);
-      }
+      position_type
+      position () const {return pos_;}
 
       void
       release () {pos_.map_ = 0;}
@@ -65,6 +63,13 @@ namespace odb
       if (session::has_current ())
         session::current ().erase<element_type> (db, id);
     }
+
+    static void
+    erase (const position_type& p)
+    {
+      if (p.map_ != 0)
+        session::current ().erase<element_type> (p);
+    }
   };
 
   // Unique pointers don't work with the object cache.
@@ -80,7 +85,12 @@ namespace odb
     struct insert_guard
     {
       insert_guard (const position_type&) {}
-      void release () {}
+
+      position_type
+      position () const {return position_type ();}
+
+      void
+      release () {}
     };
 
     static position_type
@@ -94,6 +104,9 @@ namespace odb
 
     static void
     erase (database&, const id_type&) {}
+
+    static void
+    erase (const position_type&) {}
   };
 
   // Caching traits for objects passed by reference. Only if the object
@@ -108,12 +121,19 @@ namespace odb
     typedef typename object_traits<element_type>::pointer_type pointer_type;
     typedef typename object_traits<element_type>::id_type id_type;
 
-    struct position_type {};
+    typedef
+    typename pointer_cache_traits<pointer_type>::position_type
+    position_type;
 
     struct insert_guard
     {
       insert_guard (const position_type&) {}
-      void release () {}
+
+      position_type
+      position () const {return position_type ();}
+
+      void
+      release () {}
     };
 
     static position_type
diff --git a/odb/result.hxx b/odb/result.hxx
index e87374e..cc7495f 100644
--- a/odb/result.hxx
+++ b/odb/result.hxx
@@ -77,10 +77,10 @@ namespace odb
 
   protected:
     virtual void
-    current (object_type&) = 0;
+    load (object_type&) = 0;
 
     virtual id_type
-    current_id () = 0;
+    load_id () = 0;
 
     virtual void
     next () = 0;
diff --git a/odb/result.txx b/odb/result.txx
index 603ee54..1cbf6f7 100644
--- a/odb/result.txx
+++ b/odb/result.txx
@@ -25,20 +25,17 @@ namespace odb
     {
       if (!session::has_current ())
       {
-        // Non-const pointer.
-        //
-        unrestricted_pointer_type p (object_traits::create ());
-        object_type& r (unrestricted_pointer_traits::get_ref (p));
-
-        current (pointer_type (p));
-        current (r);
+        unrestricted_pointer_type up (object_traits::create ());
+        object_type& obj (unrestricted_pointer_traits::get_ref (up));
+        current (pointer_type (up));
+        load (obj);
       }
       else
       {
-        const id_type& id (current_id ());
-
         // First check the session.
         //
+        const id_type& id (load_id ());
+
         pointer_type p (
           pointer_cache_traits<pointer_type>::find (database (), id));
 
@@ -50,14 +47,12 @@ namespace odb
 
           typename
             pointer_cache_traits<unrestricted_pointer_type>::insert_guard ig (
-            pointer_cache_traits<unrestricted_pointer_type>::insert (
-              database (), id, up));
-
-          object_type& r (unrestricted_pointer_traits::get_ref (up));
+              pointer_cache_traits<unrestricted_pointer_type>::insert (
+                database (), id, up));
 
+          object_type& obj (unrestricted_pointer_traits::get_ref (up));
           current (pointer_type (up));
-          current (r);
-
+          load (obj);
           ig.release ();
         }
       }
@@ -72,22 +67,19 @@ namespace odb
 
   template <typename T>
   void result_iterator<T>::
-  load (object_type& x)
+  load (object_type& obj)
   {
     if (res_->end ())
       return;
 
     if (!session::has_current ())
-      res_->current (x);
+      res_->load (obj);
     else
     {
-      const id_type& id (res_->current_id ());
-
       typename reference_cache_traits<object_type>::insert_guard ig (
         reference_cache_traits<object_type>::insert (
-          res_->database (), id, x));
-
-      res_->current (x);
+          res_->database (), res_->load_id (), obj));
+      res_->load (obj);
       ig.release ();
     }
   }