diff --git a/libgda/gda-ddl-column.c b/libgda/gda-ddl-column.c
index b8c1bc70b6962c11bdfda44ccc1cde648d050204..ac3057e673c9485e0c0c0272db44c68ba1d60f08 100644
--- a/libgda/gda-ddl-column.c
+++ b/libgda/gda-ddl-column.c
@@ -336,6 +336,7 @@ gda_ddl_column_parse_node (GdaDdlBuildable *buildable,
 {
   g_return_val_if_fail (buildable,FALSE);
   g_return_val_if_fail (node,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   /*TODO: Appropriate error should be set an returned. 
    * It should be added to the header file first 
@@ -448,6 +449,7 @@ gda_ddl_column_write_node (GdaDdlBuildable *buildable,
 {
   g_return_val_if_fail (buildable,FALSE);
   g_return_val_if_fail (rootnode,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   GdaDdlColumn *self = GDA_DDL_COLUMN (buildable);
 
@@ -548,7 +550,8 @@ _gda_ddl_column_set_type (GdaDdlColumn *self,
 {
   g_return_if_fail (self);
   g_return_if_fail (type);
-  //	g_return_if_fail (!*error);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
+
   GdaDdlColumnPrivate *priv = gda_ddl_column_get_instance_private (self);
   GType ttype = gda_g_type_from_string (type);
   if (ttype != G_TYPE_INVALID){
@@ -997,6 +1000,7 @@ gda_ddl_column_prepare_create  (GdaDdlColumn *self,
 {
   g_return_val_if_fail(self,FALSE);
   g_return_val_if_fail(op,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   GdaDdlColumnPrivate *priv = gda_ddl_column_get_instance_private (self);
 
@@ -1082,6 +1086,10 @@ gda_ddl_column_prepare_add (GdaDdlColumn *self,
                             GdaServerOperation *op,
                             GError **error)
 {
+  g_return_val_if_fail (self,FALSE);
+  g_return_val_if_fail (op,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
+
   GdaDdlColumnPrivate *priv = gda_ddl_column_get_instance_private (self);
 
   if(!gda_server_operation_set_value_at(op,priv->mp_name,error,
diff --git a/libgda/gda-ddl-creator.c b/libgda/gda-ddl-creator.c
index a3815c7e4d57bf6c00a1e250ee8c649455d25f1b..040574e83a461a17d624014788f78edf0e8de259 100644
--- a/libgda/gda-ddl-creator.c
+++ b/libgda/gda-ddl-creator.c
@@ -176,6 +176,7 @@ _gda_ddl_creator_validate_doc (xmlDocPtr doc,
                                GError **error)
 {
   g_return_val_if_fail (doc,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   xmlValidCtxtPtr  ctx = NULL;
 
@@ -227,6 +228,7 @@ _gda_ddl_creator_parse_doc (GdaDdlCreator *self,
 {
   g_return_val_if_fail (self,FALSE);
   g_return_val_if_fail (doc,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   xmlChar         *schema_name = NULL;
   xmlNodePtr       node        = NULL;
@@ -359,6 +361,7 @@ gda_ddl_creator_parse_file_from_path (GdaDdlCreator *self,
 {
   g_return_val_if_fail (self,FALSE);
   g_return_val_if_fail (xmlfile,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
   g_return_val_if_fail (_gda_ddl_creator_dtd,FALSE);
 
   xmlDocPtr doc = NULL;
@@ -413,6 +416,7 @@ gda_ddl_creator_validate_file_from_path (const gchar *xmlfile,
 {
   g_return_val_if_fail (xmlfile,FALSE);
   g_return_val_if_fail (_gda_ddl_creator_dtd,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   xmlDocPtr doc = NULL;
 
@@ -523,6 +527,9 @@ gda_ddl_creator_get_view (GdaDdlCreator *self,
                           const gchar *schema,
                           const gchar *name)
 {
+  g_return_val_if_fail (self,NULL);
+  g_return_val_if_fail (name,NULL);
+
   GdaDdlCreatorPrivate *priv = gda_ddl_creator_get_instance_private (self);
 
   GList *it = NULL;
@@ -534,7 +541,7 @@ gda_ddl_creator_get_view (GdaDdlCreator *self,
     if (!gda_ddl_base_compare (iobj,GDA_DDL_BASE(it)))
       {
         gda_ddl_base_free (iobj);
-      return GDA_DDL_VIEW(it);
+        return GDA_DDL_VIEW(it);
       }
 
   gda_ddl_base_free (iobj);
@@ -558,6 +565,7 @@ gda_ddl_creator_parse_cnc (GdaDdlCreator *self,
 {
   g_return_val_if_fail (self,FALSE);
   g_return_val_if_fail (cnc,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   if (!gda_connection_is_opened (cnc))
     return FALSE;
@@ -630,6 +638,7 @@ gda_ddl_creator_append_table (GdaDdlCreator *self,
                               const GdaDdlTable *table)
 {
   g_return_if_fail (self);
+  g_return_if_fail (table);
 
   GdaDdlCreatorPrivate *priv = gda_ddl_creator_get_instance_private (self);
 
@@ -650,6 +659,7 @@ gda_ddl_creator_append_view (GdaDdlCreator *self,
                              const GdaDdlView *view)
 {
   g_return_if_fail (self);
+  g_return_if_fail (view);
 
   GdaDdlCreatorPrivate *priv = gda_ddl_creator_get_instance_private (self);
 
@@ -689,6 +699,7 @@ gda_ddl_creator_perform_operation (GdaDdlCreator *self,
 {
   g_return_val_if_fail (self,FALSE);
   g_return_val_if_fail (cnc,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   if (!gda_connection_is_opened (cnc))
     {
@@ -731,7 +742,8 @@ gda_ddl_creator_perform_operation (GdaDdlCreator *self,
       g_value_set_string (schema ,gda_ddl_base_get_schema (it->data));
       g_value_set_string (name   ,gda_ddl_base_get_name   (it->data));
 
-      mobj = gda_meta_struct_complement (mstruct,GDA_META_DB_TABLE,catalog,schema,name,error);
+      /* We need to ignore error in the following call */
+      mobj = gda_meta_struct_complement (mstruct,GDA_META_DB_TABLE,catalog,schema,name,NULL);
 
       if (mobj)
         {
@@ -791,6 +803,7 @@ gda_ddl_creator_write_to_file (GdaDdlCreator *self,
 {
   g_return_val_if_fail (self,FALSE);
   g_return_val_if_fail (file,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
   
   gchar *filepath = g_file_get_path (file);
   gboolean res = gda_ddl_creator_write_to_path (self,filepath,error);
@@ -817,6 +830,7 @@ gda_ddl_creator_write_to_path (GdaDdlCreator *self,
 {
   g_return_val_if_fail (self,FALSE);
   g_return_val_if_fail (path,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
  
   GdaDdlCreatorPrivate *priv = gda_ddl_creator_get_instance_private (self);
 
@@ -873,6 +887,7 @@ gda_ddl_creator_parse_file (GdaDdlCreator *self,
   g_return_val_if_fail (self,FALSE);
   g_return_val_if_fail (xmlfile,FALSE);
   g_return_val_if_fail (_gda_ddl_creator_dtd,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   GFileInputStream *istream = NULL;
   xmlDocPtr doc = NULL;
diff --git a/libgda/gda-ddl-fkey.c b/libgda/gda-ddl-fkey.c
index d1732afe84cb5ce1f1ca1f04e241bc72b1c0aee8..f8f5978962962e724b74d271555fcb458245c498 100644
--- a/libgda/gda-ddl-fkey.c
+++ b/libgda/gda-ddl-fkey.c
@@ -102,21 +102,23 @@ gda_ddl_fkey_new (void)
 /**
  * gda_ddl_fkey_new_from_meta:
  * @metafkey: a #GdaMetaTableForeignKey instance
- * 
- * Create a new instance from the corresponding meta object. If @metafkey is %NULL, 
+ *
+ * Create a new instance from the corresponding meta object. If @metafkey is %NULL,
  * this function is identical to gda_ddl_fkey_new()
  *
  */
 GdaDdlFkey*
 gda_ddl_fkey_new_from_meta (GdaMetaTableForeignKey *metafkey)
 {
+  g_return_val_if_fail (metafkey,NULL);
+
   if (!metafkey)
     return gda_ddl_fkey_new();
 
   GdaMetaDbObject *refobject = GDA_META_DB_OBJECT (metafkey->meta_table);
 
   GdaDdlFkey *fkey = gda_ddl_fkey_new ();
-  
+
   gda_ddl_fkey_set_ref_table (fkey,refobject->obj_full_name);
 
   for (gint i = 0; i < metafkey->cols_nb; i++)
@@ -143,7 +145,7 @@ gda_ddl_fkey_new_from_meta (GdaMetaTableForeignKey *metafkey)
     default:
       break;
     }
-  
+
   policy = GDA_META_TABLE_FOREIGN_KEY_ON_DELETE_POLICY(metafkey);
   switch (policy)
     {
@@ -235,7 +237,8 @@ gda_ddl_fkey_parse_node (GdaDdlBuildable *buildable,
 {
   g_return_val_if_fail (buildable,FALSE);
   g_return_val_if_fail (node, FALSE);
-  
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
+
   /*
    *    <fkey reftable="products" onupdate="NO_ACTION" ondelete="NO_ACTION">
    *        <fk_field name="column_name" reffield="column_name"/>
@@ -336,6 +339,7 @@ gda_ddl_fkey_write_node (GdaDdlBuildable  *buildable,
 {
   g_return_val_if_fail (buildable, FALSE);
   g_return_val_if_fail (rootnode,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   GdaDdlFkey *self = GDA_DDL_FKEY (buildable);
   GdaDdlFkeyPrivate *priv = gda_ddl_fkey_get_instance_private (self);
@@ -345,7 +349,7 @@ gda_ddl_fkey_write_node (GdaDdlBuildable  *buildable,
 
   xmlNewProp (node,BAD_CAST gdaddlfkeynodes[GDA_DDL_FKEY_REFTABLE],
               BAD_CAST priv->mp_ref_table);
-  
+
   xmlNewProp (node,BAD_CAST gdaddlfkeynodes[GDA_DDL_FKEY_ONUPDATE],
               BAD_CAST priv->m_onupdate);
 
@@ -382,7 +386,7 @@ gda_ddl_fkey_buildable_interface_init (GdaDdlBuildableInterface *iface)
  * @self: An object #GdaDdlFkey
  *
  * Return: ON DELETE action as a string. If the action is not set then the string corresponding to
- * NO_ACTION is returned. 
+ * NO_ACTION is returned.
  *
  * Since: 6.0
  */
@@ -399,16 +403,19 @@ gda_ddl_fkey_get_ondelete (GdaDdlFkey *self)
 /**
  * gda_ddl_fkey_get_ondelete_id:
  * @self: a #GdaDdlFkey object
- * 
+ *
  * The default value is %NO_ACTION
  *
- * Return: ON DELETE action as a #GdaDdlFkeyReferenceAction.
+ * Return: ON DELETE action as a #GdaDdlFkeyReferenceAction. If %NULL is passed as argument then
+ * a special value %GDA_DDL_FKEY_ERROR is returned.
  *
  * Since: 6.0
  */
 GdaDdlFkeyReferenceAction
 gda_ddl_fkey_get_ondelete_id (GdaDdlFkey *self)
 {
+  g_return_val_if_fail (self,GDA_DDL_FKEY_ERROR);
+
   GdaDdlFkeyPrivate *priv = gda_ddl_fkey_get_instance_private (self);
 
   return priv->m_ondelete;
@@ -483,6 +490,8 @@ gda_ddl_fkey_get_onupdate (GdaDdlFkey *self)
 GdaDdlFkeyReferenceAction
 gda_ddl_fkey_get_onupdate_id (GdaDdlFkey *self)
 {
+  g_return_val_if_fail (self,GDA_DDL_FKEY_ERROR);
+
   GdaDdlFkeyPrivate *priv = gda_ddl_fkey_get_instance_private (self);
 
   return priv->m_onupdate;
@@ -597,7 +606,7 @@ gda_ddl_fkey_set_field (GdaDdlFkey  *self,
  * @op: a #GdaServerOperation to populate
  * @error: error container
  *
- * Prepare @op object for execution by populating with information stored in @self. 
+ * Prepare @op object for execution by populating with information stored in @self.
  *
  * Returns: %TRUE if no error or %FALSE otherwise.
  *
@@ -608,6 +617,10 @@ gda_ddl_fkey_prepare_create  (GdaDdlFkey *self,
                               GdaServerOperation *op,
                               GError **error)
 {
+  g_return_val_if_fail (self,FALSE);
+  g_return_val_if_fail (op,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
+
   GdaDdlFkeyPrivate *priv = gda_ddl_fkey_get_instance_private (self);
 
   if (!gda_server_operation_set_value_at(op,
diff --git a/libgda/gda-ddl-fkey.h b/libgda/gda-ddl-fkey.h
index 2c7678e8f3d75e25cf4647424e38158abfc7d575..e3f3b30f5473234ff00f5b78653fc6bb8f467973 100644
--- a/libgda/gda-ddl-fkey.h
+++ b/libgda/gda-ddl-fkey.h
@@ -54,7 +54,8 @@ typedef enum {
     GDA_DDL_FKEY_SET_NULL,
     GDA_DDL_FKEY_RESTRICT,
     GDA_DDL_FKEY_SET_DEFAULT,
-    GDA_DDL_FKEY_CASCADE
+    GDA_DDL_FKEY_CASCADE,
+    GDA_DDL_FKEY_ERROR
 } GdaDdlFkeyReferenceAction;
 
 
diff --git a/libgda/gda-ddl-table.c b/libgda/gda-ddl-table.c
index 31c05dfa2ca3518d183d4f01a87ee1c2ff19087b..d0f0f93826e3d8dabbb2dd123f151f8f420bdbdd 100644
--- a/libgda/gda-ddl-table.c
+++ b/libgda/gda-ddl-table.c
@@ -212,6 +212,7 @@ gda_ddl_table_parse_node (GdaDdlBuildable *buildable,
 {
   g_return_val_if_fail (buildable,FALSE);
   g_return_val_if_fail (node, FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   GdaDdlTable *self = GDA_DDL_TABLE (buildable);
 
@@ -277,6 +278,7 @@ gda_ddl_table_write_node (GdaDdlBuildable *buildable,
 {
   g_return_val_if_fail (buildable,FALSE);
   g_return_val_if_fail (rootnode,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   GdaDdlTable *self = GDA_DDL_TABLE (buildable);
   GdaDdlTablePrivate *priv = gda_ddl_table_get_instance_private (self);
@@ -477,6 +479,10 @@ gda_ddl_table_prepare_create (GdaDdlTable *self,
                               GdaServerOperation *op,
                               GError **error)
 {
+  g_return_val_if_fail (self,FALSE);
+  g_return_val_if_fail (op,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
+
   GdaDdlTablePrivate *priv = gda_ddl_table_get_instance_private (self);
 
   if (!gda_server_operation_set_value_at(op,
@@ -554,6 +560,7 @@ gda_ddl_table_update (GdaDdlTable *self,
   g_return_val_if_fail (self,FALSE);
   g_return_val_if_fail (obj,FALSE);
   g_return_val_if_fail (cnc,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
  
   if (!gda_connection_is_opened(cnc))
     return FALSE;
@@ -645,6 +652,7 @@ gda_ddl_table_create (GdaDdlTable *self,
 {
   g_return_val_if_fail (self,FALSE);
   g_return_val_if_fail (cnc,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   if (!gda_connection_is_opened(cnc))
     return FALSE;
@@ -745,6 +753,7 @@ gda_ddl_table_append_column (GdaDdlTable *self,
                              GdaDdlColumn *column)
 {
   g_return_if_fail (self);
+  g_return_if_fail (column);
 
   GdaDdlTablePrivate *priv = gda_ddl_table_get_instance_private (self);
 
@@ -765,6 +774,7 @@ gda_ddl_table_append_fkey (GdaDdlTable *self,
                            GdaDdlFkey *fkey)
 {
   g_return_if_fail (self);
+  g_return_if_fail (fkey);
 
   GdaDdlTablePrivate *priv = gda_ddl_table_get_instance_private (self);
 
diff --git a/libgda/gda-ddl-view.c b/libgda/gda-ddl-view.c
index 9790e93f6a51bedb3c2b09788b66b498193bd3b8..13421c128cef663b2d68078759986fd1ec0acd5e 100644
--- a/libgda/gda-ddl-view.c
+++ b/libgda/gda-ddl-view.c
@@ -216,6 +216,8 @@ gda_ddl_view_parse_node (GdaDdlBuildable *buildable,
                          xmlNodePtr node,
                          GError **error)
 {
+  g_return_val_if_fail (buildable,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
   GdaDdlView *self = GDA_DDL_VIEW (buildable);
   g_return_val_if_fail (node, FALSE);
 
@@ -277,6 +279,7 @@ gda_ddl_view_write_node (GdaDdlBuildable *buildable,
 {
   g_return_val_if_fail (buildable,FALSE);
   g_return_val_if_fail (rootnode,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   GdaDdlView *self = GDA_DDL_VIEW (buildable);
   GdaDdlViewPrivate *priv = gda_ddl_view_get_instance_private (self);
@@ -468,6 +471,7 @@ gda_ddl_view_create (GdaDdlView *self,
 {
   g_return_val_if_fail (self,FALSE);
   g_return_val_if_fail (cnc,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
   g_return_val_if_fail (gda_connection_is_opened(cnc),FALSE); 
 
   gda_lockable_lock((GdaLockable*)cnc);
@@ -518,6 +522,7 @@ gda_ddl_view_prepare_create (GdaDdlView *self,
 {
   g_return_val_if_fail (self,FALSE);
   g_return_val_if_fail (op,FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL,FALSE);
 
   GdaDdlViewPrivate *priv = gda_ddl_view_get_instance_private (self);
 
@@ -565,6 +570,8 @@ gda_ddl_view_prepare_create (GdaDdlView *self,
 GdaDdlView*
 gda_ddl_view_new_from_meta (GdaMetaView *view)
 {
+  g_return_val_if_fail (view,NULL);
+
   if (!view)
     return gda_ddl_view_new();