[tracker/wip/carlosg/refcount-dead-man-switch] libtracker-data: Add consistency check

[Carlos Garnacho <carlosg src gnome org>]

commit c08cad0b4e4d9d0092af535ab215622e9011096a
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Jul 31 02:24:43 2019 +0200

    libtracker-data: Add consistency check
    
    The dreaded database refcounting issue is still rampaging in some
    users. We can't detect all databases that are broken, but we can
    detect the fact that it broke in a more elegant way than a myriad
    seemingly unrelated breaks.
    
    Just drop the database and reindex from scratch in that case.

 src/libtracker-data/tracker-data-manager.c | 34 ++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
---
diff --git a/src/libtracker-data/tracker-data-manager.c b/src/libtracker-data/tracker-data-manager.c
index 116b1d4a9..010c4755c 100644
--- a/src/libtracker-data/tracker-data-manager.c
+++ b/src/libtracker-data/tracker-data-manager.c
@@ -4149,6 +4149,30 @@ update_ontology_last_modified (TrackerDataManager  *manager,
        }
 }
 
+static gboolean
+check_db_consistency (TrackerDBInterface *iface)
+{
+       TrackerDBStatement *stmt;
+       TrackerDBCursor *cursor = NULL;
+       gboolean is_inconsistent = FALSE;
+
+       stmt = tracker_db_interface_create_statement (iface, TRACKER_DB_STATEMENT_CACHE_TYPE_SELECT, NULL,
+                                                     "SELECT ID FROM \"rdfs:Resource\" "
+                                                     "LEFT OUTER JOIN Resource ON ID LIMIT 1");
+
+       if (stmt) {
+               cursor = tracker_db_statement_start_cursor (stmt, NULL);
+               g_object_unref (stmt);
+       }
+
+       if (cursor) {
+               is_inconsistent = tracker_db_cursor_iter_next (cursor, NULL, NULL);
+               g_object_unref (cursor);
+       }
+
+       return !is_inconsistent;
+}
+
 static gboolean
 tracker_data_manager_initable_init (GInitable     *initable,
                                     GCancellable  *cancellable,
@@ -4214,6 +4238,16 @@ tracker_data_manager_initable_init (GInitable     *initable,
 
        iface = tracker_db_manager_get_writable_db_interface (manager->db_manager);
 
+       if (!read_only && !check_db_consistency (iface)) {
+               g_set_error (error,
+                            TRACKER_DATA_ONTOLOGY_ERROR,
+                            TRACKER_DATA_UNSUPPORTED_LOCATION,
+                            "Database is inconsistent, reindexing from scratch");
+
+               tracker_db_manager_remove_all (manager->db_manager);
+               return FALSE;
+       }
+
 #ifndef DISABLE_JOURNAL
        if (manager->journal_check && is_first_time_index) {
                TrackerDBJournalReader *journal_reader;