[tracker/wip/carlosg/sparql1.1: 134/145] libtracker-data: Do not error out on unknown graphs

[Carlos Garnacho <carlosg src gnome org>]

commit 66eb44a666676a07d8b920b345272b669f7acb91
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Jul 14 23:45:06 2019 +0200

    libtracker-data: Do not error out on unknown graphs
    
    Those should be an equivalent to an empty graph instead. In order to
    have the query valid for future executions where the graph might
    exist, use the unionGraph with a check for its graph column.

 src/libtracker-data/tracker-sparql.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql.c b/src/libtracker-data/tracker-sparql.c
index ea9dca198..1e6745567 100644
--- a/src/libtracker-data/tracker-sparql.c
+++ b/src/libtracker-data/tracker-sparql.c
@@ -1142,16 +1142,8 @@ _add_quad (TrackerSparql  *sparql,
        triple_context = TRACKER_TRIPLE_CONTEXT (sparql->current_state.context);
        ontologies = tracker_data_manager_get_ontologies (sparql->data_manager);
 
-       if (tracker_token_get_literal (graph)) {
+       if (tracker_token_get_literal (graph))
                graph_db = tracker_token_get_idstring (graph);
-               if (tracker_data_manager_find_graph (sparql->data_manager, graph_db) == 0) {
-                       g_set_error (error, TRACKER_SPARQL_ERROR,
-                                    TRACKER_SPARQL_ERROR_UNKNOWN_GRAPH,
-                                    "Unknown graph '%s'",
-                                    tracker_token_get_idstring (graph));
-                       return FALSE;
-               }
-       }
 
        if (tracker_token_get_literal (predicate)) {
                gboolean share_table = TRUE;
@@ -1780,13 +1772,22 @@ _end_triples_block (TrackerSparql  *sparql,
                } else if (table->predicate_path) {
                        _append_string_printf (sparql, "\"%s\"", table->sql_db_tablename);
                } else {
-                       if (table->graph) {
-                               _append_string_printf (sparql, "\"%s\".\"%s\"",
+                       if (table->graph &&
+                           tracker_data_manager_find_graph (sparql->data_manager, table->graph)) {
+                               _append_string_printf (sparql, "\"%s\".\"%s\" ",
                                                       table->graph,
                                                       table->sql_db_tablename);
                        } else {
-                               _append_string_printf (sparql, "\"unionGraph_%s\" ",
-                                                      table->sql_db_tablename);
+                               if (table->graph) {
+                                       _append_string_printf (sparql,
+                                                              "(SELECT * FROM \"unionGraph_%s\" "
+                                                              "WHERE graph = (SELECT ID FROM Resource WHERE 
Uri = \"%s\")) ",
+                                                              table->sql_db_tablename,
+                                                              table->graph);
+                               } else {
+                                       _append_string_printf (sparql, "\"unionGraph_%s\" ",
+                                                              table->sql_db_tablename);
+                               }
                        }
                }