[libgda] Added the GDA_CONNECTION_FEATURE_ASYNC_EXEC option to test if a connection supports async. execution

[Vivien Malerba <vivien src gnome org>]

commit ec24a4358a8c31ba94b9dcaf1b34a2f73ac423a1
Author: Vivien Malerba <malerba gnome-db org>
Date:   Mon Mar 11 21:59:37 2013 +0100

    Added the GDA_CONNECTION_FEATURE_ASYNC_EXEC option to test if a connection supports async. execution

 libgda/gda-connection.c      |   13 ++++++++++++-
 libgda/gda-connection.h      |    9 ++++++---
 libgda/gda-server-provider.c |    3 +++
 3 files changed, 21 insertions(+), 4 deletions(-)
---
diff --git a/libgda/gda-connection.c b/libgda/gda-connection.c
index b4960ad..7b5ce8b 100644
--- a/libgda/gda-connection.c
+++ b/libgda/gda-connection.c
@@ -3092,7 +3092,7 @@ get_task_index (GdaConnection *cnc, guint task_id, gboolean *out_completed, gboo
 }
 
 /*
- * This callback is called from the GdaServerProvider object
+ * This callback is called from the GdaServerProvider object, from the handle_async() method
  */
 static void
 async_stmt_exec_cb (G_GNUC_UNUSED GdaServerProvider *provider, GdaConnection *cnc, guint task_id,
@@ -3257,6 +3257,14 @@ gda_connection_async_statement_execute (GdaConnection *cnc, GdaStatement *stmt,
                return 0;
        }
 
+       if (!PROV_CLASS (cnc->priv->provider_obj)->handle_async) {
+               g_set_error (error, GDA_CONNECTION_ERROR, GDA_CONNECTION_UNSUPPORTED_ASYNC_EXEC_ERROR,
+                            _("Asynchronous execution is not supported"));
+               gda_connection_unlock (GDA_LOCKABLE (cnc));
+               g_object_unref ((GObject*) cnc);
+               return 0;
+       }
+
        id = cnc->priv->next_task_id ++;
        task = cnc_task_new (id, stmt, model_usage, col_types, params, need_last_insert_row);
        g_array_append_val (cnc->priv->waiting_tasks, task);
@@ -3337,6 +3345,7 @@ gda_connection_async_fetch_result (GdaConnection *cnc, guint task_id, GdaSet **l
        gboolean is_completed;
        GObject *obj = NULL;
        g_return_val_if_fail (GDA_IS_CONNECTION (cnc), NULL);
+       g_return_val_if_fail (cnc->priv->provider_obj, NULL);
 
        if (! gda_connection_trylock ((GdaLockable*) cnc)) {
                g_set_error (error, GDA_CONNECTION_ERROR, GDA_CONNECTION_CANT_LOCK_ERROR,
@@ -4337,6 +4346,8 @@ gda_connection_supports_feature (GdaConnection *cnc, GdaConnectionFeature featur
        g_return_val_if_fail (GDA_IS_CONNECTION (cnc), FALSE);
        g_return_val_if_fail (cnc->priv->provider_obj, FALSE);
 
+       if (feature == GDA_CONNECTION_FEATURE_ASYNC_EXEC)
+               return PROV_CLASS (cnc->priv->provider_obj)->handle_async ? TRUE : FALSE;
        return gda_server_provider_supports_feature (cnc->priv->provider_obj, cnc, feature);
 }
 
diff --git a/libgda/gda-connection.h b/libgda/gda-connection.h
index 67f48d1..3140121 100644
--- a/libgda/gda-connection.h
+++ b/libgda/gda-connection.h
@@ -63,7 +63,8 @@ typedef enum {
        GDA_CONNECTION_TASK_NOT_FOUND_ERROR,
        GDA_CONNECTION_UNSUPPORTED_THREADS_ERROR,
        GDA_CONNECTION_CLOSED_ERROR,
-       GDA_CONNECTION_META_DATA_CONTEXT_ERROR
+       GDA_CONNECTION_META_DATA_CONTEXT_ERROR,
+       GDA_CONNECTION_UNSUPPORTED_ASYNC_EXEC_ERROR
 } GdaConnectionError;
 
 #define GDA_CONNECTION_NONEXIST_DSN_ERROR GDA_CONNECTION_DSN_NOT_FOUND_ERROR
@@ -218,6 +219,7 @@ typedef enum {
  * @GDA_CONNECTION_FEATURE_VIEWS: test for views support
  * @GDA_CONNECTION_FEATURE_XA_TRANSACTIONS: test for distributed transactions support
  * @GDA_CONNECTION_FEATURE_MULTI_THREADING: test for native multi-threading support
+ * @GDA_CONNECTION_FEATURE_ASYNC_EXEC: test if connection supports asynchronous execution
  * @GDA_CONNECTION_FEATURE_LAST: not used
  *
  * Used in gda_connection_supports_feature() and gda_server_provider_supports_feature() to test if a 
connection
@@ -242,6 +244,7 @@ typedef enum {
        GDA_CONNECTION_FEATURE_XA_TRANSACTIONS,
        
        GDA_CONNECTION_FEATURE_MULTI_THREADING,
+       GDA_CONNECTION_FEATURE_ASYNC_EXEC,
 
        GDA_CONNECTION_FEATURE_LAST
 } GdaConnectionFeature;
@@ -337,7 +340,7 @@ gchar               *gda_connection_quote_sql_identifier (GdaConnection *cnc, co
 gchar               *gda_connection_statement_to_sql     (GdaConnection *cnc,
                                                          GdaStatement *stmt, GdaSet *params, 
GdaStatementSqlFlag flags,
                                                          GSList **params_used, GError **error);
-/* synchronous exec */
+/* synchronous execution */
 gboolean             gda_connection_statement_prepare    (GdaConnection *cnc,
                                                          GdaStatement *stmt, GError **error);
 GObject             *gda_connection_statement_execute    (GdaConnection *cnc, GdaStatement *stmt, GdaSet 
*params, 
@@ -354,7 +357,7 @@ GdaDataModel        *gda_connection_statement_execute_select_full (GdaConnection
 gint                 gda_connection_statement_execute_non_select (GdaConnection *cnc, GdaStatement *stmt,
                                                                  GdaSet *params, GdaSet **last_insert_row, 
GError **error);
 
-/* Async. execution */
+/* asynchronous execution */
 guint                gda_connection_async_statement_execute (GdaConnection *cnc, GdaStatement *stmt, GdaSet 
*params, 
                                                             GdaStatementModelUsage model_usage, GType 
*col_types,
                                                             gboolean need_last_insert_row, 
diff --git a/libgda/gda-server-provider.c b/libgda/gda-server-provider.c
index 64b21cf..126e10d 100644
--- a/libgda/gda-server-provider.c
+++ b/libgda/gda-server-provider.c
@@ -656,6 +656,9 @@ gda_server_provider_supports_feature (GdaServerProvider *provider, GdaConnection
        g_return_val_if_fail (GDA_IS_SERVER_PROVIDER (provider), FALSE);
        g_return_val_if_fail (!cnc || GDA_IS_CONNECTION (cnc), FALSE);
 
+       if (feature == GDA_CONNECTION_FEATURE_ASYNC_EXEC)
+               return CLASS(provider)->handle_async ? TRUE : FALSE;;
+
        if (cnc)
                gda_lockable_lock ((GdaLockable*) cnc);
        if (CLASS (provider)->supports_feature)