[tracker/wip/carlosg/property-paths: 5/6] libtracker-data: Implement alternative path sequences

[Carlos Garnacho <carlosg src gnome org>]

commit 0d5c1a65f5a1ea331d438b863e9b6fff14b2dff3
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Dec 24 19:11:57 2018 +0100

    libtracker-data: Implement alternative path sequences
    
    The alternative path operator '|' allows multiplexing the ways to get a
    value. For example:
    
      { ?u nie:title|nfo:fileName 'foo' }
    
    will return elements whose title or filename matches the given string.

 src/libtracker-data/tracker-sparql.c | 52 ++++++++++++++++++++++++++++++++----
 1 file changed, 47 insertions(+), 5 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql.c b/src/libtracker-data/tracker-sparql.c
index d2e9477c4..d123c6330 100644
--- a/src/libtracker-data/tracker-sparql.c
+++ b/src/libtracker-data/tracker-sparql.c
@@ -570,6 +570,18 @@ _prepend_path_element (TrackerSparql      *sparql,
                                       path_elem->data.composite.child1->name,
                                       path_elem->data.composite.child2->name);
                break;
+       case TRACKER_PATH_OPERATOR_ALTERNATIVE:
+               _append_string_printf (sparql,
+                                      "\"%s\" (ID, value, graph) AS "
+                                      "(SELECT ID, value, graph "
+                                      "FROM \"%s\" "
+                                      "UNION ALL "
+                                      "SELECT ID, value, graph "
+                                      "FROM \"%s\") ",
+                                      path_elem->name,
+                                      path_elem->data.composite.child1->name,
+                                      path_elem->data.composite.child2->name);
+               break;
        case TRACKER_PATH_OPERATOR_ZEROORMORE:
                _append_string_printf (sparql,
                                       "\"%s\" (ID, value, graph) AS "
@@ -610,9 +622,6 @@ _prepend_path_element (TrackerSparql      *sparql,
                                       path_elem->data.composite.child1->name,
                                       path_elem->data.composite.child1->name);
                break;
-       default:
-               g_assert_not_reached ();
-               break;
        }
 
        tracker_sparql_swap_builder (sparql, old);
@@ -4199,14 +4208,47 @@ static gboolean
 translate_PathAlternative (TrackerSparql  *sparql,
                            GError        **error)
 {
+       GPtrArray *path_elems;
+
+       path_elems = g_ptr_array_new ();
+
        /* PathAlternative ::= PathSequence ( '|' PathSequence )*
         */
        _call_rule (sparql, NAMED_RULE_PathSequence, error);
+       g_ptr_array_add (path_elems, sparql->current_state.path);
 
-       if (_accept (sparql, RULE_TYPE_LITERAL, LITERAL_PATH_ALTERNATIVE)) {
-               _unimplemented ("Alternative property path");
+       while (_accept (sparql, RULE_TYPE_LITERAL, LITERAL_PATH_ALTERNATIVE)) {
+               _call_rule (sparql, NAMED_RULE_PathSequence, error);
+               g_ptr_array_add (path_elems, sparql->current_state.path);
        }
 
+       if (path_elems->len > 1) {
+               TrackerPathElement *path_elem;
+               gint i;
+
+               path_elem = tracker_path_element_operator_new (TRACKER_PATH_OPERATOR_ALTERNATIVE,
+                                                              g_ptr_array_index (path_elems, 0),
+                                                              g_ptr_array_index (path_elems, 1));
+               tracker_select_context_add_path_element (TRACKER_SELECT_CONTEXT (sparql->context),
+                                                        path_elem);
+               _prepend_path_element (sparql, path_elem);
+
+               for (i = 2; i < path_elems->len; i++) {
+                       TrackerPathElement *child;
+
+                       child = g_ptr_array_index (path_elems, i);
+                       path_elem = tracker_path_element_operator_new (TRACKER_PATH_OPERATOR_ALTERNATIVE,
+                                                                      child, path_elem);
+                       tracker_select_context_add_path_element (TRACKER_SELECT_CONTEXT (sparql->context),
+                                                                path_elem);
+                       _prepend_path_element (sparql, path_elem);
+               }
+
+               sparql->current_state.path = path_elem;
+       }
+
+       g_ptr_array_unref (path_elems);
+
        return TRUE;
 }