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, 21 insertions, 2 deletions

diff --git a/odb/mysql/transaction-impl.cxx b/odb/mysql/transaction-impl.cxx
index 86cccbe..24c511f 100644
--- a/odb/mysql/transaction-impl.cxx
+++ b/odb/mysql/transaction-impl.cxx
@@ -14,11 +14,15 @@ namespace odb
   namespace mysql
   {
     transaction_impl::
+    transaction_impl (database_type& db)
+        : odb::transaction_impl (db)
+    {
+    }
+
+    transaction_impl::
     transaction_impl (connection_ptr c)
         : odb::transaction_impl (c->database (), *c), connection_ (c)
     {
-      if (mysql_real_query (connection_->handle (), "begin", 5) != 0)
-        translate_error (*connection_);
     }
 
     transaction_impl::
@@ -27,6 +31,21 @@ 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 ();
+      }
+
+      if (mysql_real_query (connection_->handle (), "begin", 5) != 0)
+        translate_error (*connection_);
+    }
+
+    void transaction_impl::
     commit ()
     {
       connection_->clear ();