Add odb::connection class

This abstract class represents a connection to the database. One can
use it to start a transaction or to execute a native statement out
of a transaction.

Before we had concrete connection classes in the database runtime
libraries (e.g., odb::mysql::connection). Now these classes derive
from odb::connection.

1 files changed, 12 insertions, 2 deletions

diff --git a/odb/mysql/database.ixx b/odb/mysql/database.ixx
index 5791222..399fbdc 100644
--- a/odb/mysql/database.ixx
+++ b/odb/mysql/database.ixx
@@ -7,10 +7,20 @@ namespace odb
 {
   namespace mysql
   {
-    inline details::shared_ptr<database::connection_type> database::
+    inline connection_ptr database::
     connection ()
     {
-      return factory_->connect ();
+      // Go through the virtual connection_() function instead of
+      // directly to allow overriding.
+      //
+      return connection_ptr (
+        static_cast<mysql::connection*> (connection_ ()));
+    }
+
+    inline transaction_impl* database::
+    begin ()
+    {
+      return connection ()->begin ();
     }
   }
 }