[tracker/wip/carlosg/tracker-3.0-api-breaks: 74/92] libtracker-sparql: Make TrackerNotifier queries asynchronous

[Carlos Garnacho <carlosg src gnome org>]

commit 1d39f13ee3ffe3a8947ca4c7f57b7489be24559c
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Jan 27 00:19:54 2020 +0100

    libtracker-sparql: Make TrackerNotifier queries asynchronous
    
    Synchronous queries are very untimely here, since the events are
    handled within TrackerDirectConnection mutex, triggering deadlocks
    here.
    
    Doing the queries asynchronously defers this to a thread pool, so
    the mutex will be contended from 2 separate threads, if at all.

 src/libtracker-sparql/tracker-notifier.c | 50 ++++++++++++++++++++++----------
 1 file changed, 35 insertions(+), 15 deletions(-)
---
diff --git a/src/libtracker-sparql/tracker-notifier.c b/src/libtracker-sparql/tracker-notifier.c
index a1381a817..db05dc1fb 100644
--- a/src/libtracker-sparql/tracker-notifier.c
+++ b/src/libtracker-sparql/tracker-notifier.c
@@ -342,25 +342,22 @@ create_extra_info_query (TrackerNotifier           *notifier,
 }
 
 static void
-tracker_notifier_query_extra_info (TrackerNotifier           *notifier,
-                                   TrackerNotifierEventCache *cache)
+query_extra_info_cb (GObject      *object,
+                     GAsyncResult *res,
+                     gpointer      user_data)
 {
+       TrackerNotifierEventCache *cache = user_data;
+       TrackerSparqlConnection *conn;
        TrackerNotifierPrivate *priv;
        TrackerSparqlCursor *cursor;
        TrackerNotifierEvent *event;
        GSequenceIter *iter;
-       gchar *sparql;
        gint col;
        gint64 id;
 
-       sparql = create_extra_info_query (notifier, cache);
-       if (!sparql)
-               return;
-
-       priv = tracker_notifier_get_instance_private (notifier);
-       cursor = tracker_sparql_connection_query (priv->connection, sparql,
-                                                 NULL, NULL);
-       g_free (sparql);
+       priv = tracker_notifier_get_instance_private (cache->notifier);
+       conn = TRACKER_SPARQL_CONNECTION (object);
+       cursor = tracker_sparql_connection_query_finish (conn, res, NULL);
 
        iter = g_sequence_get_begin_iter (cache->sequence);
 
@@ -386,6 +383,28 @@ tracker_notifier_query_extra_info (TrackerNotifier           *notifier,
        }
 
        g_object_unref (cursor);
+
+       tracker_notifier_emit_events (cache);
+       _tracker_notifier_event_cache_free (cache);
+}
+
+static void
+tracker_notifier_query_extra_info (TrackerNotifier           *notifier,
+                                   TrackerNotifierEventCache *cache)
+{
+       TrackerNotifierPrivate *priv;
+       gchar *sparql;
+
+       sparql = create_extra_info_query (notifier, cache);
+       if (!sparql)
+               return;
+
+       priv = tracker_notifier_get_instance_private (notifier);
+       tracker_sparql_connection_query_async (priv->connection, sparql,
+                                              NULL,
+                                              query_extra_info_cb,
+                                              cache);
+       g_free (sparql);
 }
 
 void
@@ -397,11 +416,12 @@ _tracker_notifier_event_cache_flush_events (TrackerNotifierEventCache *cache)
        if (g_sequence_is_empty (cache->sequence))
                _tracker_notifier_event_cache_free (cache);
 
-       if (priv->flags & TRACKER_NOTIFIER_FLAG_QUERY_URN)
+       if (priv->flags & TRACKER_NOTIFIER_FLAG_QUERY_URN) {
                tracker_notifier_query_extra_info (notifier, cache);
-
-       tracker_notifier_emit_events (cache);
-       _tracker_notifier_event_cache_free (cache);
+       } else {
+               tracker_notifier_emit_events (cache);
+               _tracker_notifier_event_cache_free (cache);
+       }
 }
 
 static void