Ground work for multi-database support

All generated code now includes database id. The database-specific
database class interface has been updated to include all the database
operations. The database-specific tests now use this interface.

12 files changed, 398 insertions, 212 deletions

diff --git a/odb/database.hxx b/odb/database.hxx
index 64f9d44..99205e7 100644
--- a/odb/database.hxx
+++ b/odb/database.hxx
@@ -63,7 +63,7 @@ namespace odb
     typename object_traits<T>::id_type
     persist (const typename object_traits<T>::pointer_type& obj_ptr);
 
-    // Throw object_not_persistent if not found.
+    // Load an object. Throw object_not_persistent if not found.
     //
     template <typename T>
     typename object_traits<T>::pointer_type
@@ -73,6 +73,8 @@ namespace odb
     void
     load (const typename object_traits<T>::id_type& id, T& object);
 
+    // Reload an object.
+    //
     template <typename T>
     void
     reload (T& object);
@@ -101,7 +103,7 @@ namespace odb
     void
     reload (const typename object_traits<T>::pointer_type& obj_ptr);
 
-    // Return NULL/false if not found.
+    // Loan an object if found. Return NULL/false if not found.
     //
     template <typename T>
     typename object_traits<T>::pointer_type
@@ -250,8 +252,14 @@ namespace odb
     tracer_type*
     tracer () const;
 
+    // Database id.
+    //
+  public:
+    database_id
+    id () const;
+
   protected:
-    database ();
+    database (database_id);
 
   private:
     database (const database&);
@@ -264,22 +272,61 @@ namespace odb
     connection_ () = 0;
 
   protected:
-    template <typename T>
+    template <typename T, database_id DB>
+    typename object_traits<T>::id_type
+    persist_ (T&);
+
+    template <typename T, database_id DB>
     typename object_traits<T>::id_type
     persist_ (const typename object_traits<T>::pointer_type&);
 
-    template <typename T>
+    template <typename T, database_id DB>
+    typename object_traits<T>::pointer_type
+    load_ (const typename object_traits<T>::id_type&);
+
+    template <typename T, database_id DB>
+    void
+    load_ (const typename object_traits<T>::id_type&, T&);
+
+    template <typename T, database_id DB>
+    void
+    reload_ (T&);
+
+    template <typename T, database_id DB>
+    typename object_traits<T>::pointer_type
+    find_ (const typename object_traits<T>::id_type&);
+
+    template <typename T, database_id DB>
+    bool
+    find_ (const typename object_traits<T>::id_type&, T&);
+
+    template <typename T, database_id DB>
+    void
+    update_ (T&);
+
+    template <typename T, database_id DB>
     void
     update_ (const typename object_traits<T>::pointer_type&);
 
-    template <typename T>
+    template <typename T, database_id DB>
+    void
+    erase_ (const typename object_traits<T>::id_type&);
+
+    template <typename T, database_id DB>
+    void
+    erase_ (T&);
+
+    template <typename T, database_id DB>
     void
     erase_ (const typename object_traits<T>::pointer_type&);
 
-    template <typename T, class_kind kind>
+    template <typename T,
+              database_id DB,
+              class_kind kind = class_traits<T>::kind>
     struct query_;
 
   protected:
+    database_id id_;
     tracer_type* tracer_;
   };
 }
diff --git a/odb/database.ixx b/odb/database.ixx
index 4a00a74..aeffdec 100644
--- a/odb/database.ixx
+++ b/odb/database.ixx
@@ -7,11 +7,17 @@
 namespace odb
 {
   inline database::
-  database ()
-      : tracer_ (0)
+  database (database_id id)
+      : id_ (id), tracer_ (0)
   {
   }
 
+  inline database_id database::
+  id () const
+  {
+    return id_;
+  }
+
   inline connection_ptr database::
   connection ()
   {
@@ -38,6 +44,13 @@ namespace odb
 
   template <typename T>
   inline typename object_traits<T>::id_type database::
+  persist (T& obj)
+  {
+    return persist_<T, id_default> (obj);
+  }
+
+  template <typename T>
+  inline typename object_traits<T>::id_type database::
   persist (T* p)
   {
     typedef typename object_traits<T>::pointer_type object_pointer;
@@ -48,7 +61,7 @@ namespace odb
     //
     const object_pointer& pobj (p);
 
-    return persist_<T> (pobj);
+    return persist_<T, id_default> (pobj);
   }
 
   template <typename T, template <typename> class P>
@@ -63,7 +76,7 @@ namespace odb
     //
     const object_pointer& pobj (p);
 
-    return persist_<T> (pobj);
+    return persist_<T, id_default> (pobj);
   }
 
   template <typename T, typename A1, template <typename, typename> class P>
@@ -78,7 +91,7 @@ namespace odb
     //
     const object_pointer& pobj (p);
 
-    return persist_<T> (pobj);
+    return persist_<T, id_default> (pobj);
   }
 
   template <typename T, template <typename> class P>
@@ -101,29 +114,42 @@ namespace odb
   inline typename object_traits<T>::id_type database::
   persist (const typename object_traits<T>::pointer_type& pobj)
   {
-    return persist_<T> (pobj);
+    return persist_<T, id_default> (pobj);
   }
 
   template <typename T>
   inline typename object_traits<T>::pointer_type database::
-  find (const typename object_traits<T>::id_type& id)
+  load (const typename object_traits<T>::id_type& id)
   {
-    // T is always object_type.
-    //
+    return load_<T, id_default> (id);
+  }
 
-    // Compiler error pointing here? Perhaps the object doesn't have the
-    // default constructor?
-    //
-    return object_traits<T>::find (*this, id);
+  template <typename T>
+  inline void database::
+  load (const typename object_traits<T>::id_type& id, T& obj)
+  {
+    return load_<T, id_default> (id, obj);
+  }
+
+  template <typename T>
+  inline typename object_traits<T>::pointer_type database::
+  find (const typename object_traits<T>::id_type& id)
+  {
+    return find_<T, id_default> (id);
   }
 
   template <typename T>
   inline bool database::
   find (const typename object_traits<T>::id_type& id, T& obj)
   {
-    // T is always object_type.
-    //
-    return object_traits<T>::find (*this, id, obj);
+    return find_<T, id_default> (id, obj);
+  }
+
+  template <typename T>
+  inline void database::
+  reload (T& obj)
+  {
+    reload_<T, id_default> (obj);
   }
 
   template <typename T>
@@ -172,6 +198,13 @@ namespace odb
 
   template <typename T>
   inline void database::
+  update (T& obj)
+  {
+    update_<T, id_default> (obj);
+  }
+
+  template <typename T>
+  inline void database::
   update (T* p)
   {
     typedef typename object_traits<T>::pointer_type object_pointer;
@@ -182,7 +215,7 @@ namespace odb
     //
     const object_pointer& pobj (p);
 
-    update_<T> (pobj);
+    update_<T, id_default> (pobj);
   }
 
   template <typename T, template <typename> class P>
@@ -197,7 +230,7 @@ namespace odb
     //
     const object_pointer& pobj (p);
 
-    update_<T> (pobj);
+    update_<T, id_default> (pobj);
   }
 
   template <typename T, typename A1, template <typename, typename> class P>
@@ -212,7 +245,7 @@ namespace odb
     //
     const object_pointer& pobj (p);
 
-    update_<T> (pobj);
+    update_<T, id_default> (pobj);
   }
 
   template <typename T, template <typename> class P>
@@ -235,42 +268,21 @@ namespace odb
   inline void database::
   update (const typename object_traits<T>::pointer_type& pobj)
   {
-    update_<T> (pobj);
+    update_<T, id_default> (pobj);
   }
 
   template <typename T>
   inline void database::
-  update (T& obj)
+  erase (const typename object_traits<T>::id_type& id)
   {
-    // T can be const T while object_type will always be T.
-    //
-    typedef typename odb::object_traits<T>::object_type object_type;
-    typedef odb::object_traits<object_type> object_traits;
-
-    // Compiler error pointing here? Perhaps the object is readonly or
-    // doesn't have an object id? Such objects cannot be updated.
-    //
-    object_traits::update (*this, obj);
+    return erase_<T, id_default> (id);
   }
 
   template <typename T>
   inline void database::
-  update_ (const typename object_traits<T>::pointer_type& pobj)
+  erase (T& obj)
   {
-    // T can be const T while object_type will always be T.
-    //
-    typedef typename odb::object_traits<T>::object_type object_type;
-    typedef odb::object_traits<object_type> object_traits;
-
-    typedef typename odb::object_traits<T>::pointer_type pointer_type;
-    typedef odb::pointer_traits<pointer_type> pointer_traits;
-
-    T& obj (pointer_traits::get_ref (pobj));
-
-    // Compiler error pointing here? Perhaps the object is readonly or
-    // doesn't have an object id? Such objects cannot be updated.
-    //
-    object_traits::update (*this, obj);
+    return erase_<T, id_default> (obj);
   }
 
   template <typename T>
@@ -285,7 +297,7 @@ namespace odb
     //
     const object_pointer& pobj (p);
 
-    erase_<T> (pobj);
+    erase_<T, id_default> (pobj);
   }
 
   template <typename T, template <typename> class P>
@@ -300,7 +312,7 @@ namespace odb
     //
     const object_pointer& pobj (p);
 
-    erase_<T> (pobj);
+    erase_<T, id_default> (pobj);
   }
 
   template <typename T, typename A1, template <typename, typename> class P>
@@ -315,7 +327,7 @@ namespace odb
     //
     const object_pointer& pobj (p);
 
-    erase_<T> (pobj);
+    erase_<T, id_default> (pobj);
   }
 
   template <typename T, template <typename> class P>
@@ -338,37 +350,7 @@ namespace odb
   inline void database::
   erase (const typename object_traits<T>::pointer_type& pobj)
   {
-    erase_<T> (pobj);
-  }
-
-  template <typename T>
-  inline void database::
-  erase_ (const typename object_traits<T>::pointer_type& pobj)
-  {
-    typedef typename object_traits<T>::pointer_type pointer_type;
-    typedef pointer_traits<pointer_type> pointer_traits;
-
-    erase<T> (pointer_traits::get_ref (pobj));
-  }
-
-  template <typename T>
-  inline void database::
-  erase (const typename object_traits<T>::id_type& id)
-  {
-    // T is always object_type.
-    //
-    object_traits<T>::erase (*this, id);
-  }
-
-  template <typename T>
-  inline void database::
-  erase (T& obj)
-  {
-    // T can be const T while object_type will always be T.
-    //
-    typedef typename object_traits<T>::object_type object_type;
-
-    object_traits<object_type>::erase (*this, obj);
+    erase_<T, id_default> (pobj);
   }
 
   template <typename T>
@@ -404,7 +386,7 @@ namespace odb
   {
     // T is always object_type.
     //
-    return object_traits<T>::erase_query (*this, q);
+    return object_traits_impl<T, id_default>::erase_query (*this, q);
   }
 
   template <typename T>
@@ -428,6 +410,92 @@ namespace odb
     return query<T> (odb::query<T> (q), cache);
   }
 
+  // Implementations (i.e., the *_() functions).
+  //
+  template <typename T, database_id DB>
+  inline typename object_traits<T>::pointer_type database::
+  find_ (const typename object_traits<T>::id_type& id)
+  {
+    // T is always object_type.
+    //
+
+    // Compiler error pointing here? Perhaps the object doesn't have the
+    // default constructor?
+    //
+    return object_traits_impl<T, DB>::find (*this, id);
+  }
+
+  template <typename T, database_id DB>
+  inline bool database::
+  find_ (const typename object_traits<T>::id_type& id, T& obj)
+  {
+    // T is always object_type.
+    //
+    return object_traits_impl<T, DB>::find (*this, id, obj);
+  }
+
+  template <typename T, database_id DB>
+  inline void database::
+  update_ (T& obj)
+  {
+    // T can be const T while object_type will always be T.
+    //
+    typedef typename object_traits<T>::object_type object_type;
+
+    // Compiler error pointing here? Perhaps the object is readonly or
+    // doesn't have an object id? Such objects cannot be updated.
+    //
+    object_traits_impl<object_type, DB>::update (*this, obj);
+  }
+
+  template <typename T, database_id DB>
+  inline void database::
+  update_ (const typename object_traits<T>::pointer_type& pobj)
+  {
+    // T can be const T while object_type will always be T.
+    //
+    typedef typename object_traits<T>::object_type object_type;
+    typedef typename object_traits<T>::pointer_type pointer_type;
+
+    T& obj (pointer_traits<pointer_type>::get_ref (pobj));
+
+    // Compiler error pointing here? Perhaps the object is readonly or
+    // doesn't have an object id? Such objects cannot be updated.
+    //
+    object_traits_impl<object_type, DB>::update (*this, obj);
+  }
+
+  template <typename T, database_id DB>
+  inline void database::
+  erase_ (const typename object_traits<T>::id_type& id)
+  {
+    // T is always object_type.
+    //
+    object_traits_impl<T, DB>::erase (*this, id);
+  }
+
+  template <typename T, database_id DB>
+  inline void database::
+  erase_ (T& obj)
+  {
+    // T can be const T while object_type will always be T.
+    //
+    typedef typename object_traits<T>::object_type object_type;
+
+    object_traits_impl<object_type, DB>::erase (*this, obj);
+  }
+
+  template <typename T, database_id DB>
+  inline void database::
+  erase_ (const typename object_traits<T>::pointer_type& pobj)
+  {
+    typedef typename object_traits<T>::pointer_type pointer_type;
+
+    erase_<T, DB> (pointer_traits<pointer_type>::get_ref (pobj));
+  }
+
+  // execute()
+  //
   inline unsigned long long database::
   execute (const char* statement)
   {
diff --git a/odb/database.txx b/odb/database.txx
index 7ac19d7..23ea712 100644
--- a/odb/database.txx
+++ b/odb/database.txx
@@ -10,13 +10,30 @@
 namespace odb
 {
   template <typename T>
+  result<T> database::
+  query (const odb::query<T>& q, bool cache)
+  {
+    // T is always object_type. We also don't need to check for transaction
+    // here; object_traits::query () does this.
+    //
+    result<T> r (query_<T, id_default>::call (*this, q));
+
+    if (cache)
+      r.cache ();
+
+    return r;
+  }
+
+  // Implementations (i.e., the *_() functions).
+  //
+  template <typename T, database_id DB>
   typename object_traits<T>::id_type database::
-  persist (T& obj)
+  persist_ (T& obj)
   {
     // T can be const T while object_type will always be T.
     //
-    typedef typename odb::object_traits<T>::object_type object_type;
-    typedef odb::object_traits<object_type> object_traits;
+    typedef typename object_traits<T>::object_type object_type;
+    typedef object_traits_impl<object_type, DB> object_traits;
 
     object_traits::persist (*this, obj);
 
@@ -26,19 +43,18 @@ namespace odb
     return object_traits::id (obj);
   }
 
-  template <typename T>
+  template <typename T, database_id DB>
   typename object_traits<T>::id_type database::
   persist_ (const typename object_traits<T>::pointer_type& pobj)
   {
     // T can be const T while object_type will always be T.
     //
-    typedef typename odb::object_traits<T>::object_type object_type;
-    typedef odb::object_traits<object_type> object_traits;
+    typedef typename object_traits<T>::object_type object_type;
+    typedef typename object_traits<T>::pointer_type pointer_type;
 
-    typedef typename odb::object_traits<T>::pointer_type pointer_type;
-    typedef odb::pointer_traits<pointer_type> pointer_traits;
+    typedef object_traits_impl<object_type, DB> object_traits;
 
-    T& obj (pointer_traits::get_ref (pobj));
+    T& obj (pointer_traits<pointer_type>::get_ref (pobj));
     object_traits::persist (*this, obj);
 
     // Get the canonical object pointer and insert it into object cache.
@@ -49,81 +65,60 @@ namespace odb
     return object_traits::id (obj);
   }
 
-  template <typename T>
+  template <typename T, database_id DB>
   typename object_traits<T>::pointer_type database::
-  load (const typename object_traits<T>::id_type& id)
+  load_ (const typename object_traits<T>::id_type& id)
   {
     // T is always object_type.
     //
     typedef typename object_traits<T>::pointer_type pointer_type;
-    typedef odb::pointer_traits<pointer_type> pointer_traits;
 
-    pointer_type r (find<T> (id));
+    pointer_type r (find_<T, DB> (id));
 
-    if (pointer_traits::null_ptr (r))
+    if (pointer_traits<pointer_type>::null_ptr (r))
       throw object_not_persistent ();
 
     return r;
   }
 
-  template <typename T>
+  template <typename T, database_id DB>
   void database::
-  load (const typename object_traits<T>::id_type& id, T& obj)
+  load_ (const typename object_traits<T>::id_type& id, T& obj)
   {
-    if (!find<T> (id, obj))
+    if (!find_<T, DB> (id, obj))
       throw object_not_persistent ();
   }
 
-  template <typename T>
+  template <typename T, database_id DB>
   void database::
-  reload (T& obj)
+  reload_ (T& obj)
   {
-    // T should be object_type (cannot be const).
+    // T should be object_type (cannot be const). We also don't need to
+    // check for transaction here; object_traits::reload () does this.
     //
-    typedef odb::object_traits<T> object_traits;
-
-    // We don't need to check for transaction here;
-    // object_traits::reload () does this.
-
-    if (!object_traits::reload (*this, obj))
+    if (!object_traits_impl<T, DB>::reload (*this, obj))
       throw object_not_persistent ();
   }
 
-  template <typename T>
-  struct database::query_<T, class_object>
+  template <typename T, database_id DB>
+  struct database::query_<T, DB, class_object>
   {
+    template <typename Q>
     static result<T>
-    call (database& db, const odb::query<T>& q)
+    call (database& db, const Q& q)
     {
-      return object_traits<T>::query (db, q);
+      return object_traits_impl<T, DB>::query (db, q);
     }
   };
 
-  template <typename T>
-  struct database::query_<T, class_view>
+  template <typename T, database_id DB>
+  struct database::query_<T, DB, class_view>
   {
+    template <typename Q>
     static result<T>
-    call (database& db, const odb::query<T>& q)
+    call (database& db, const Q& q)
     {
-      return view_traits<T>::query (db, q);
+      return view_traits_impl<T, DB>::query (db, q);
     }
   };
-
-  template <typename T>
-  result<T> database::
-  query (const odb::query<T>& q, bool cache)
-  {
-    // T is always object_type.
-    //
-
-    // We don't need to check for transaction here;
-    // object_traits::query () does this.
-
-    result<T> r (query_<T, class_traits<T>::kind>::call (*this, q));
-
-    if (cache)
-      r.cache ();
-
-    return r;
-  }
 }
diff --git a/odb/forward.hxx b/odb/forward.hxx
index 4c5e4b9..ff4a531 100644
--- a/odb/forward.hxx
+++ b/odb/forward.hxx
@@ -7,6 +7,8 @@
 
 #include <odb/pre.hxx>
 
+#include <cstddef> // std::size_t
+
 #include <odb/details/export.hxx>
 #include <odb/details/shared-ptr-fwd.hxx>
 
@@ -42,25 +44,50 @@ namespace odb
   // Implementation details.
   //
 
+  // Keep real databases first since their enumerators are used as array
+  // indexes
+  //
+  enum database_id
+  {
+    id_mysql,
+    id_sqlite,
+    id_pgsql,
+    id_oracle,
+    id_mssql,
+    id_default
+  };
+
+  // Number of real databases in the database_id enum.
+  //
+  const std::size_t database_count = id_default;
+
+  // Traits.
+  //
   class access
   {
   public:
     template <typename T>
     class object_traits;
 
+    template <typename T, database_id DB>
+    class object_traits_impl;
+
     template <typename T, typename P>
     class object_factory;
 
     template <typename T>
     class view_traits;
 
+    template <typename T, database_id DB>
+    class view_traits_impl;
+
     template <typename T, typename P>
     class view_factory;
 
     template <typename T, typename P>
     class pointer_factory;
 
-    template <typename T>
+    template <typename T, database_id DB>
     class composite_value_traits;
 
     template <typename C>
@@ -70,9 +97,15 @@ namespace odb
   template <typename T>
   struct object_traits;
 
+  template <typename T, database_id DB>
+  struct object_traits_impl;
+
   template <typename T>
   struct view_traits;
 
+  template <typename T, database_id DB>
+  struct view_traits_impl;
+
   // Cache traits.
   //
   template <typename T> struct no_id_pointer_cache_traits;
diff --git a/odb/polymorphic-info.hxx b/odb/polymorphic-info.hxx
index abed648..54291ce 100644
--- a/odb/polymorphic-info.hxx
+++ b/odb/polymorphic-info.hxx
@@ -86,14 +86,12 @@ namespace odb
 
   // Register concrete type T in the root's map.
   //
-  template <typename T>
+  template <typename T, database_id DB>
   struct polymorphic_entry
   {
     typedef T object_type;
-    typedef odb::object_traits<object_type> object_traits;
-
+    typedef object_traits_impl<object_type, DB> object_traits;
     typedef typename object_traits::root_type root_type;
-    typedef odb::object_traits<root_type> root_traits;
 
     polymorphic_entry ();
     ~polymorphic_entry ();
diff --git a/odb/polymorphic-map.hxx b/odb/polymorphic-map.hxx
index c3c1374..5d23e6f 100644
--- a/odb/polymorphic-map.hxx
+++ b/odb/polymorphic-map.hxx
@@ -66,11 +66,11 @@ namespace odb
     discriminator_map discriminator_map_;
   };
 
-  template <typename R>
+  template <typename R, database_id DB>
   struct polymorphic_entry_impl
   {
     typedef R root_type;
-    typedef object_traits<root_type> root_traits;
+    typedef object_traits_impl<root_type, DB> root_traits;
     typedef polymorphic_concrete_info<root_type> info_type;
 
     static void
@@ -103,18 +103,18 @@ namespace odb
     return r;
   }
 
-  template <typename T, typename R>
+  template <typename T, database_id DB, typename R>
   struct dispatch_load
   {
     static void
     call (database& db, T& obj, std::size_t d)
     {
-      object_traits<T>::load_ (db, obj, d);
+      object_traits_impl<T, DB>::load_ (db, obj, d);
     }
   };
 
-  template <typename R>
-  struct dispatch_load<R, R>
+  template <typename R, database_id DB>
+  struct dispatch_load<R, DB, R>
   {
     static void
     call (database&, R&, std::size_t)
@@ -123,7 +123,7 @@ namespace odb
     }
   };
 
-  template <typename T, bool auto_id>
+  template <typename T, database_id DB, bool auto_id>
   struct dispatch_persist
   {
     static void
@@ -131,23 +131,24 @@ namespace odb
     {
       // Top-level call, no dynamic type checking.
       //
-      object_traits<T>::persist (db, obj, true, false);
+      object_traits_impl<T, DB>::persist (db, obj, true, false);
     }
   };
 
-  template <typename T>
-  struct dispatch_persist<T, true>
+  template <typename T, database_id DB>
+  struct dispatch_persist<T, DB, true>
   {
     static void
     call (database& db, const T& obj)
     {
       // Top-level call, no dynamic type checking.
       //
-      object_traits<T>::persist (db, const_cast<T&> (obj), true, false);
+      object_traits_impl<T, DB>::persist (
+        db, const_cast<T&> (obj), true, false);
     }
   };
 
-  template <typename T>
+  template <typename T, database_id DB>
   bool dispatch_impl (
     typename polymorphic_concrete_info<
       typename object_traits<T>::root_type>::call_type c,
@@ -155,9 +156,9 @@ namespace odb
     const typename object_traits<T>::root_type* pobj,
     const void* arg)
   {
-    typedef object_traits<T> derived_traits;
+    typedef object_traits_impl<T, DB> derived_traits;
     typedef typename derived_traits::root_type root_type;
-    typedef object_traits<root_type> root_traits;
+    typedef object_traits_impl<root_type, DB> root_traits;
     typedef typename root_traits::id_type id_type;
     typedef polymorphic_concrete_info<root_type> info_type;
 
@@ -175,7 +176,7 @@ namespace odb
       }
     case info_type::call_persist:
       {
-        dispatch_persist<T, root_traits::auto_id>::call (
+        dispatch_persist<T, DB, root_traits::auto_id>::call (
           db,
           *static_cast<const T*> (pobj));
         break;
@@ -208,7 +209,7 @@ namespace odb
       }
     case info_type::call_load:
       {
-        dispatch_load<T, root_type>::call (
+        dispatch_load<T, DB, root_type>::call (
           db,
           *const_cast<T*> (static_cast<const T*> (pobj)),
           *static_cast<const std::size_t*> (arg));
diff --git a/odb/polymorphic-map.ixx b/odb/polymorphic-map.ixx
index 4dbd174..546d997 100644
--- a/odb/polymorphic-map.ixx
+++ b/odb/polymorphic-map.ixx
@@ -4,17 +4,17 @@
 
 namespace odb
 {
-  template <typename T>
-  inline polymorphic_entry<T>::
+  template <typename T, database_id DB>
+  inline polymorphic_entry<T, DB>::
   polymorphic_entry ()
   {
-    polymorphic_entry_impl<root_type>::insert (object_traits::info);
+    polymorphic_entry_impl<root_type, DB>::insert (object_traits::info);
   }
 
-  template <typename T>
-    inline polymorphic_entry<T>::
+  template <typename T, database_id DB>
+  inline polymorphic_entry<T, DB>::
   ~polymorphic_entry ()
   {
-      polymorphic_entry_impl<root_type>::erase (object_traits::info);
+    polymorphic_entry_impl<root_type, DB>::erase (object_traits::info);
   }
 }
diff --git a/odb/polymorphic-map.txx b/odb/polymorphic-map.txx
index d7b6e36..26534a6 100644
--- a/odb/polymorphic-map.txx
+++ b/odb/polymorphic-map.txx
@@ -39,8 +39,8 @@ namespace odb
   // polymorphic_entry_impl
   //
 
-  template <typename R>
-  void polymorphic_entry_impl<R>::
+  template <typename R, database_id DB>
+  void polymorphic_entry_impl<R, DB>::
   insert (const info_type& i)
   {
     // VC10 cannot grok constructor call syntax here.
@@ -56,8 +56,8 @@ namespace odb
     pm->discriminator_map_[&i.discriminator] = &i;
   }
 
-  template <typename R>
-  void polymorphic_entry_impl<R>::
+  template <typename R, database_id DB>
+  void polymorphic_entry_impl<R, DB>::
   erase (const info_type& i)
   {
     // VC10 cannot grok constructor call syntax here.
diff --git a/odb/query.hxx b/odb/query.hxx
index 9f889db..d5d0a19 100644
--- a/odb/query.hxx
+++ b/odb/query.hxx
@@ -7,6 +7,7 @@
 
 #include <odb/pre.hxx>
 
+#include <odb/forward.hxx>
 #include <odb/traits.hxx>
 
 namespace odb
@@ -21,16 +22,16 @@ namespace odb
   // we need straight tables instead of aliases.
   //
   //
-  template <typename T, typename Tag, bool dummy = true>
+  template <typename T, database_id DB, typename Tag, bool dummy = true>
   struct alias_traits;
 
-  template <typename T>
+  template <typename T, database_id DB>
   struct query_columns_base;
 
-  template <typename T, typename Alias>
+  template <typename T, database_id DB, typename Alias>
   struct query_columns;
 
-  template <typename T, typename Alias>
+  template <typename T, database_id DB, typename Alias>
   struct pointer_query_columns;
 
   // Object pointer syntax wrapper.
@@ -56,29 +57,33 @@ namespace odb
   // we have to use the impl trick below instead of simply having kind
   // as a second template argument with a default value.
   //
-  template <typename T, class_kind kind>
+  template <typename T, database_id DB, class_kind kind>
   struct query_selector_impl;
 
-  template <typename T>
-  struct query_selector_impl<T, class_object>
+  template <typename T, database_id DB>
+  struct query_selector_impl<T, DB, class_object>
   {
-    typedef typename object_traits<T>::query_base_type base_type;
-    typedef query_columns<T, access::object_traits<T> > columns_type;
+    typedef typename object_traits_impl<T, DB>::query_base_type base_type;
+
+    typedef
+    query_columns<T, DB, access::object_traits_impl<T, DB> >
+    columns_type;
   };
 
-  template <typename T>
-  struct query_selector_impl<T, class_view>
+  template <typename T, database_id DB>
+  struct query_selector_impl<T, DB, class_view>
   {
-    typedef typename view_traits<T>::query_base_type base_type;
-    typedef typename view_traits<T>::query_columns columns_type;
+    typedef typename view_traits_impl<T, DB>::query_base_type base_type;
+    typedef typename view_traits_impl<T, DB>::query_columns columns_type;
   };
 
-  template <typename T>
-  struct query_selector: query_selector_impl<T, class_traits<T>::kind>
+  template <typename T, database_id DB>
+  struct query_selector: query_selector_impl<T, DB, class_traits<T>::kind>
   {
   };
 
-  template <typename T, typename Q = typename query_selector<T>::base_type>
+  template <typename T,
+            typename B = typename query_selector<T, id_default>::base_type>
   class query;
 
   namespace core
diff --git a/odb/schema-catalog-impl.hxx b/odb/schema-catalog-impl.hxx
index 71d5d89..9b94cf1 100644
--- a/odb/schema-catalog-impl.hxx
+++ b/odb/schema-catalog-impl.hxx
@@ -35,8 +35,9 @@ namespace odb
   struct LIBODB_EXPORT schema_catalog_entry
   {
     schema_catalog_entry (
+      database_id id,
       const char* name,
-      bool (*entry) (database&, unsigned short pass, bool drop));
+      bool (*create_function) (database&, unsigned short pass, bool drop));
   };
 }
 
diff --git a/odb/schema-catalog.cxx b/odb/schema-catalog.cxx
index 7f00c3c..cd1ded4 100644
--- a/odb/schema-catalog.cxx
+++ b/odb/schema-catalog.cxx
@@ -5,6 +5,7 @@
 #include <map>
 #include <vector>
 
+#include <odb/database.hxx>
 #include <odb/exceptions.hxx>
 #include <odb/schema-catalog.hxx>
 #include <odb/schema-catalog-impl.hxx>
@@ -19,8 +20,9 @@ namespace odb
   // for example, for foreign key generation.
   //
   typedef bool (*create_function) (database&, unsigned short pass, bool drop);
+  typedef pair<database_id, string> key;
   typedef vector<create_function> create_functions;
-  struct schema_catalog_impl: map<string, create_functions> {};
+  struct schema_catalog_impl: map<key, create_functions> {};
 
   schema_catalog_impl* schema_catalog_init::catalog = 0;
   size_t schema_catalog_init::count = 0;
@@ -29,8 +31,7 @@ namespace odb
   create_schema (database& db, const string& name)
   {
     const schema_catalog_impl& c (*schema_catalog_init::catalog);
-
-    schema_catalog_impl::const_iterator i (c.find (name));
+    schema_catalog_impl::const_iterator i (c.find (key (db.id (), name)));
 
     if (i == c.end ())
       throw unknown_schema (name);
@@ -94,9 +95,9 @@ namespace odb
   // schema_catalog_entry
   //
   schema_catalog_entry::
-  schema_catalog_entry (const char* name, create_function entry)
+  schema_catalog_entry (database_id id, const char* name, create_function cf)
   {
     schema_catalog_impl& c (*schema_catalog_init::catalog);
-    c[name].push_back (entry);
+    c[key(id, name)].push_back (cf);
   }
 }
diff --git a/odb/traits.hxx b/odb/traits.hxx
index 0743dba..3711601 100644
--- a/odb/traits.hxx
+++ b/odb/traits.hxx
@@ -99,17 +99,16 @@ namespace odb
   //
 
   template <typename T>
+  //
+  // If a C++ compiler issues an error pointing to this struct and
+  // saying that it is incomplete, then you are most likely trying to
+  // perform a database operation on a C++ type that is not a persistent
+  // object. Or you forgot to include the corresponding -odb.hxx file.
+  //
   struct object_traits:
     access::object_traits<T>,
     access::object_factory<T, typename access::object_traits<T>::pointer_type>
   {
-    //
-    // If a C++ compiler issues an error pointing to this struct and
-    // saying that it is incomplete, then you are most likely trying to
-    // perform a database operation on a C++ type that is not a persistent
-    // object. Or you forgot to include the corresponding -odb.hxx file.
-    //
-
     typedef
     odb::pointer_traits<typename access::object_traits<T>::pointer_type>
     pointer_traits;
@@ -160,45 +159,64 @@ namespace odb
   };
 
   template <typename T, template <typename> class P>
-  struct object_traits< P<T> >
+  struct object_traits<P<T> >
   {
     struct id_type {};
   };
 
   template <typename T, typename A1, template <typename, typename> class P>
-  struct object_traits< P<T, A1> >
+  struct object_traits<P<T, A1> >
   {
     struct id_type {};
   };
 
   template <typename T, template <typename> class P>
-  struct object_traits< const P<T> >
+  struct object_traits<const P<T> >
   {
     struct id_type {};
   };
 
   template <typename T, typename A1, template <typename, typename> class P>
-  struct object_traits< const P<T, A1> >
+  struct object_traits<const P<T, A1> >
   {
     struct id_type {};
   };
 
+  template <typename T, database_id DB>
+  //
+  // If a C++ compiler issues an error pointing to this struct and
+  // saying that it is incomplete, then you are most likely trying to
+  // perform a database operation on a C++ type that is not a persistent
+  // object. Or you forgot to include the corresponding -odb.hxx file.
+  //
+  struct object_traits_impl:
+    access::object_traits_impl<T, DB>,
+    access::object_factory<T, typename access::object_traits<T>::pointer_type>
+  {
+    typedef
+    odb::pointer_traits<typename access::object_traits<T>::pointer_type>
+    pointer_traits;
+
+    typedef typename access::object_traits<T>::object_type object_type;
+    typedef typename access::object_traits<T>::pointer_type pointer_type;
+    typedef typename pointer_traits::const_pointer_type const_pointer_type;
+  };
+
   //
   // view_traits
   //
 
   template <typename T>
+  //
+  // If a C++ compiler issues an error pointing to this struct and
+  // saying that it is incomplete, then you are most likely trying to
+  // perform a database operation on a C++ type that is not a view
+  // Or you forgot to include the corresponding -odb.hxx file.
+  //
   struct view_traits:
     access::view_traits<T>,
     access::view_factory<T, typename access::view_traits<T>::pointer_type>
   {
-    //
-    // If a C++ compiler issues an error pointing to this struct and
-    // saying that it is incomplete, then you are most likely trying to
-    // perform a database operation on a C++ type that is not a view
-    // Or you forgot to include the corresponding -odb.hxx file.
-    //
-
     typedef
     odb::pointer_traits<typename access::view_traits<T>::pointer_type>
     pointer_traits;
@@ -227,12 +245,31 @@ namespace odb
     typedef const_pointer_type pointer_type;
   };
 
+  template <typename T, database_id DB>
+  //
+  // If a C++ compiler issues an error pointing to this struct and
+  // saying that it is incomplete, then you are most likely trying to
+  // perform a database operation on a C++ type that is not a view
+  // Or you forgot to include the corresponding -odb.hxx file.
+  //
+  struct view_traits_impl:
+    access::view_traits_impl<T, DB>,
+    access::view_factory<T, typename access::view_traits<T>::pointer_type>
+  {
+    typedef
+    odb::pointer_traits<typename access::view_traits<T>::pointer_type>
+    pointer_traits;
+
+    typedef typename access::view_traits<T>::view_type view_type;
+    typedef typename access::view_traits<T>::pointer_type pointer_type;
+  };
+
   //
   // composite_value_traits
   //
 
-  template <typename T>
-  struct composite_value_traits: access::composite_value_traits<T>
+  template <typename T, database_id DB>
+  struct composite_value_traits: access::composite_value_traits<T, DB>
   {
   };
 }