Implement support for optimistic concurrency

New pragmas: optimistic, version. New test: optimistic. New database
function: reload().

4 files changed, 34 insertions, 5 deletions

diff --git a/odb/database.hxx b/odb/database.hxx
index 7e29ddf..8ccc642 100644
--- a/odb/database.hxx
+++ b/odb/database.hxx
@@ -66,6 +66,10 @@ namespace odb
     void
     load (const typename object_traits<T>::id_type& id, T& object);
 
+    template <typename T>
+    void
+    reload (T& object);
+
     // Return NULL/false if not found.
     //
     template <typename T>
diff --git a/odb/database.txx b/odb/database.txx
index 42643aa..b019478 100644
--- a/odb/database.txx
+++ b/odb/database.txx
@@ -85,6 +85,18 @@ namespace odb
   }
 
   template <typename T>
+  void database::
+  reload (T& obj)
+  {
+    // T should be object_type (cannot be const).
+    //
+    typedef odb::object_traits<T> object_traits;
+
+    if (!object_traits::reload (*this, obj))
+      throw object_not_persistent ();
+  }
+
+  template <typename T>
   typename object_traits<T>::pointer_type database::
   find (const typename object_traits<T>::id_type& id)
   {
@@ -206,7 +218,7 @@ namespace odb
     typename object_traits::id_type id (object_traits::id (obj));
 
     object_traits::callback (*this, obj, callback_event::pre_erase);
-    object_traits::erase (*this, id);
+    object_traits::erase (*this, obj);
     pointer_cache_traits<pointer_type>::erase (*this, id);
     object_traits::callback (*this, obj, callback_event::post_erase);
   }
diff --git a/odb/exceptions.cxx b/odb/exceptions.cxx
index 60692cf..970b3b0 100644
--- a/odb/exceptions.cxx
+++ b/odb/exceptions.cxx
@@ -71,16 +71,22 @@ namespace odb
     return "object not persistent";
   }
 
-  const char* result_not_cached::
+  const char* object_already_persistent::
   what () const throw ()
   {
-    return "query result is not cached";
+    return "object already persistent";
   }
 
-  const char* object_already_persistent::
+  const char* object_changed::
   what () const throw ()
   {
-    return "object already persistent";
+    return "object changed concurrently";
+  }
+
+  const char* result_not_cached::
+  what () const throw ()
+  {
+    return "query result is not cached";
   }
 
   unknown_schema::
diff --git a/odb/exceptions.hxx b/odb/exceptions.hxx
index 698baee..5f48717 100644
--- a/odb/exceptions.hxx
+++ b/odb/exceptions.hxx
@@ -92,6 +92,12 @@ namespace odb
     what () const throw ();
   };
 
+  struct LIBODB_EXPORT object_changed: exception
+  {
+    virtual const char*
+    what () const throw ();
+  };
+
   struct LIBODB_EXPORT result_not_cached: exception
   {
     virtual const char*
@@ -140,6 +146,7 @@ namespace odb
     using odb::timeout;
     using odb::object_not_persistent;
     using odb::object_already_persistent;
+    using odb::object_changed;
     using odb::result_not_cached;
     using odb::database_exception;