[tracker/wip/carlosg/property-paths: 4/6] libtracker-data: Implement PathMod

[Carlos Garnacho <carlosg src gnome org>]

commit 862b1617269f5466c658b9a01366f0a399e44a14
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Dec 24 18:35:18 2018 +0100

    libtracker-data: Implement PathMod
    
    All three modifiers in PathMod are implemented now:
      - ?(zero or one): { ?u nfo:belongsToContainer? ?c } returns direct
        children of ?c, plus ?c itself.
      - *(zero or more): { ?u nfo:belongsToContainer* ?c } returns all children
        of ?c recursively, including ?c itself.
      - +(one or more): { ?u nfo:belongsToContainer+ ?c } returns all children
        of ?c recursively.

 src/libtracker-data/tracker-sparql.c | 60 +++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)
---
diff --git a/src/libtracker-data/tracker-sparql.c b/src/libtracker-data/tracker-sparql.c
index a1befd7f5..d2e9477c4 100644
--- a/src/libtracker-data/tracker-sparql.c
+++ b/src/libtracker-data/tracker-sparql.c
@@ -570,6 +570,46 @@ _prepend_path_element (TrackerSparql      *sparql,
                                       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 "
+                                      "(SELECT ID, ID, graph "
+                                      "FROM \"%s\" "
+                                      "UNION "
+                                      "SELECT a.ID, b.value, b.graph "
+                                      "FROM \"%s\" AS a, \"%s\" AS b "
+                                      "WHERE b.ID = a.value) ",
+                                      path_elem->name,
+                                      path_elem->data.composite.child1->name,
+                                      path_elem->data.composite.child1->name,
+                                      path_elem->name);
+               break;
+       case TRACKER_PATH_OPERATOR_ONEORMORE:
+               _append_string_printf (sparql,
+                                      "\"%s\" (ID, value, graph) AS "
+                                      "(SELECT ID, value, graph "
+                                      "FROM \"%s\" "
+                                      "UNION "
+                                      "SELECT a.ID, b.value, b.graph "
+                                      "FROM \"%s\" AS a, \"%s\" AS b "
+                                      "WHERE b.ID = a.value) ",
+                                      path_elem->name,
+                                      path_elem->data.composite.child1->name,
+                                      path_elem->data.composite.child1->name,
+                                      path_elem->name);
+               break;
+       case TRACKER_PATH_OPERATOR_ZEROORONE:
+               _append_string_printf (sparql,
+                                      "\"%s\" (ID, value, graph) AS "
+                                      "(SELECT ID, ID, graph "
+                                      "FROM \"%s\" "
+                                      "UNION ALL "
+                                      "SELECT ID, value, graph "
+                                      "FROM \"%s\") ",
+                                      path_elem->name,
+                                      path_elem->data.composite.child1->name,
+                                      path_elem->data.composite.child1->name);
+               break;
        default:
                g_assert_not_reached ();
                break;
@@ -4270,9 +4310,27 @@ static gboolean
 translate_PathMod (TrackerSparql  *sparql,
                    GError        **error)
 {
+       TrackerPathElement *path_elem;
+       TrackerPathOperator op;
+
        /* PathMod ::= '?' | '*' | '+'
         */
-       _unimplemented ("Path modifiers");
+       if (_accept (sparql, RULE_TYPE_LITERAL, LITERAL_PATH_STAR)) {
+               op = TRACKER_PATH_OPERATOR_ZEROORMORE;
+       } else if (_accept (sparql, RULE_TYPE_LITERAL, LITERAL_PATH_PLUS)) {
+               op = TRACKER_PATH_OPERATOR_ONEORMORE;
+       } else if (_accept (sparql, RULE_TYPE_LITERAL, LITERAL_PATH_OPTIONAL)) {
+               op = TRACKER_PATH_OPERATOR_ZEROORONE;
+       } else {
+               return TRUE;
+       }
+
+       path_elem = tracker_path_element_operator_new (op, sparql->current_state.path, NULL);
+       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;
+       return TRUE;
 }
 
 static gboolean