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.

7 files changed, 40 insertions, 13 deletions

diff --git a/odb/tracer/connection.cxx b/odb/tracer/connection.cxx
index 516e36a..54c233c 100644
--- a/odb/tracer/connection.cxx
+++ b/odb/tracer/connection.cxx
@@ -27,11 +27,7 @@ namespace odb
     transaction_impl* connection::
     begin ()
     {
-      if (odb::transaction::has_current ())
-        throw already_in_transaction ();
-
-      return new transaction_impl (
-        connection_ptr (inc_ref (this)));
+      return new transaction_impl (connection_ptr (inc_ref (this)));
     }
   }
 }
diff --git a/odb/tracer/database.cxx b/odb/tracer/database.cxx
index 90cfdfd..5e032ee 100644
--- a/odb/tracer/database.cxx
+++ b/odb/tracer/database.cxx
@@ -18,10 +18,10 @@ namespace odb
     transaction_impl* database::
     begin ()
     {
-      return connection ()->begin ();
+      return new transaction_impl (*this);
     }
 
-    inline connection_ptr database::
+    connection_ptr database::
     connection ()
     {
       // Go through the virtual connection_() function instead of
diff --git a/odb/tracer/database.hxx b/odb/tracer/database.hxx
index 2468583..acdad8a 100644
--- a/odb/tracer/database.hxx
+++ b/odb/tracer/database.hxx
@@ -26,7 +26,7 @@ namespace odb
       virtual
       ~database ();
 
-      transaction_impl*
+      virtual transaction_impl*
       begin ();
 
       connection_ptr
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;
diff --git a/odb/tracer/transaction-impl.hxx b/odb/tracer/transaction-impl.hxx
index f926183..b92797b 100644
--- a/odb/tracer/transaction-impl.hxx
+++ b/odb/tracer/transaction-impl.hxx
@@ -20,18 +20,19 @@ namespace odb
   {
     class LIBODB_TRACER_EXPORT transaction_impl: public odb::transaction_impl
     {
-    protected:
-      friend class connection;
-      friend class transaction;
-
+    public:
       typedef tracer::database database_type;
 
+      transaction_impl (database_type&);
       transaction_impl (connection_ptr);
 
       virtual
       ~transaction_impl ();
 
       virtual void
+      start ();
+
+      virtual void
       commit ();
 
       virtual void
diff --git a/odb/tracer/transaction.hxx b/odb/tracer/transaction.hxx
index 0dbc366..b65903d 100644
--- a/odb/tracer/transaction.hxx
+++ b/odb/tracer/transaction.hxx
@@ -38,6 +38,11 @@ namespace odb
       static transaction&
       current ();
 
+      // Set the current thread's transaction.
+      //
+      static void
+      current (transaction&);
+
     public:
       transaction_impl&
       implementation ();
diff --git a/odb/tracer/transaction.ixx b/odb/tracer/transaction.ixx
index a36c426..d936e8d 100644
--- a/odb/tracer/transaction.ixx
+++ b/odb/tracer/transaction.ixx
@@ -31,5 +31,11 @@ namespace odb
       return static_cast<transaction_impl&> (
         odb::transaction::implementation ());
     }
+
+    inline void transaction::
+    current (transaction& t)
+    {
+      odb::transaction::current (t);
+    }
   }
 }