Add support for transaction multiplexing

Also delay getting a connection until after we do all the sanity
checks (e.g., that there is no active transaction). Otherwise we
are running risk of getting blocked rather than throwing an
exception.

1 files changed, 20 insertions, 1 deletions

diff --git a/odb/tracer/transaction-impl.cxx b/odb/tracer/transaction-impl.cxx
index 2069568..bf272b3 100644
--- a/odb/tracer/transaction-impl.cxx
+++ b/odb/tracer/transaction-impl.cxx
@@ -17,12 +17,17 @@ namespace odb
   namespace tracer
   {
     transaction_impl::
+    transaction_impl (database_type& db)
+        : odb::transaction_impl (db), finalized_ (false)
+    {
+    }
+
+    transaction_impl::
     transaction_impl (connection_ptr c)
         : odb::transaction_impl (c->database (), *c),
           finalized_ (false),
           connection_ (c)
     {
-      cout << "begin transaction" << endl;
     }
 
     transaction_impl::
@@ -33,6 +38,20 @@ namespace odb
     }
 
     void transaction_impl::
+    start ()
+    {
+      // Grab a connection if we don't already have one.
+      //
+      if (connection_ == 0)
+      {
+        connection_ = static_cast<database_type&> (database_).connection ();
+        odb::transaction_impl::connection_ = connection_.get ();
+      }
+
+      cout << "begin transaction" << endl;
+    }
+
+    void transaction_impl::
     commit ()
     {
       cout << "commit transaction" << endl;