Introduce new flag to force use of iTQL queries, when applicable.

includes/admin.form.inc

@@ -80,6 +80,12 @@ function islandora_repository_admin(array $form, array &$form_state) {
           '#description' => t('Larger sites may experience a notable performance improvement when disabled due to how breadcrumbs are constructed.'),
           '#default_value' => variable_get('islandora_render_drupal_breadcrumbs', TRUE),
         ),
+        'islandora_risearch_use_itql_for_walking' => array(
+          '#type' => 'checkbox',
+          '#title' => t('Use iTQL For Transitive Queries'),
+          '#description' => t('Sparql is the preferred language for querying the resource index; however, the implementation of Sparql in Mulgara may not completely support transitive queries. On by default to maintain legacy behaviour.'),
+          '#default_value' => variable_get('islandora_risearch_use_itql_for_walking', TRUE),
+        ),
       ),
       'islandora_namespace' => array(
         '#type' => 'fieldset',

islandora.install

@@ -54,6 +54,7 @@ function islandora_uninstall() {
     'islandora_render_drupal_breadcrumbs',
     'islandora_namespace_restriction_enforced',
     'islandora_pids_allowed',
+    'islandora_risearch_use_itql_for_walking',
   );
   array_walk($variables, 'variable_del');
 }