[tracker/wip/carlosg/avoid-notifier-query] libtracker-sparql: Avoid URN queries in DBus endpoint notifications

[Carlos Garnacho <carlosg src gnome org>]

commit 9c6ce63819f782c9883b901adbbaebcd161aef55
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Jan 23 13:54:18 2022 +0100

    libtracker-sparql: Avoid URN queries in DBus endpoint notifications
    
    When a connection is proxied through a TrackerEndpointDBus, there are
    possibly 2 levels of TrackerNotifiers, one being used in the service
    itself to trigger the DBus signal, and another on any listening client
    handling those notifications.
    
    However, both of these are doing an additional query to fetch the URN
    for each of the notified elements. Since we only pass ROWIDs in the
    DBus signal to make the signal data as compact as possible, we can
    avoid this query on the service side. Any client listening to
    notifications will perform its own URN queries anyway.
    
    So avoid this piece of pointless busywork in the service side, and
    special case that the internal notifiers used by endpoints should not
    perform the query for URN data.
    
    This does not make anything noticeably faster (perhaps endpoint signal
    emission is a bit more snappy now, if anything) as all querying and
    cursor handling happens lazily in a separate thread fairly detached
    from the rest of the machinery. However it's still less CPU cycles
    used overall.

 src/libtracker-sparql/tracker-endpoint-dbus.c    |  2 ++
 src/libtracker-sparql/tracker-notifier-private.h |  2 ++
 src/libtracker-sparql/tracker-notifier.c         | 16 ++++++++++++++--
 3 files changed, 18 insertions(+), 2 deletions(-)
---
diff --git a/src/libtracker-sparql/tracker-endpoint-dbus.c b/src/libtracker-sparql/tracker-endpoint-dbus.c
index fa840e0e3..c6735603d 100644
--- a/src/libtracker-sparql/tracker-endpoint-dbus.c
+++ b/src/libtracker-sparql/tracker-endpoint-dbus.c
@@ -43,6 +43,7 @@
 
 #include "tracker-endpoint-dbus.h"
 #include "tracker-notifier.h"
+#include "tracker-notifier-private.h"
 #include "tracker-private.h"
 
 #include <gio/gio.h>
@@ -1008,6 +1009,7 @@ tracker_endpoint_dbus_initable_init (GInitable     *initable,
 
        conn = tracker_endpoint_get_sparql_connection (endpoint);
        endpoint_dbus->notifier = tracker_sparql_connection_create_notifier (conn);
+       tracker_notifier_disable_urn_query (endpoint_dbus->notifier);
        g_signal_connect (endpoint_dbus->notifier, "events",
                          G_CALLBACK (notifier_events_cb), endpoint);
 
diff --git a/src/libtracker-sparql/tracker-notifier-private.h 
b/src/libtracker-sparql/tracker-notifier-private.h
index aabe9f1bc..e808be1e2 100644
--- a/src/libtracker-sparql/tracker-notifier-private.h
+++ b/src/libtracker-sparql/tracker-notifier-private.h
@@ -39,4 +39,6 @@ _tracker_notifier_event_cache_push_event (TrackerNotifierEventCache *cache,
 
 void _tracker_notifier_event_cache_flush_events (TrackerNotifierEventCache *cache);
 
+void tracker_notifier_disable_urn_query (TrackerNotifier *notifier);
+
 #endif /* __TRACKER_NOTIFIER_PRIVATE_H__ */
diff --git a/src/libtracker-sparql/tracker-notifier.c b/src/libtracker-sparql/tracker-notifier.c
index 01081a75b..86329ce9d 100644
--- a/src/libtracker-sparql/tracker-notifier.c
+++ b/src/libtracker-sparql/tracker-notifier.c
@@ -74,7 +74,8 @@ struct _TrackerNotifierPrivate {
        TrackerSparqlStatement *local_statement;
        GAsyncQueue *queue;
        gint n_local_statement_slots;
-       gboolean querying;
+       guint querying : 1;
+       guint urn_query_disabled : 1;
        GMutex mutex;
 };
 
@@ -633,7 +634,9 @@ _tracker_notifier_event_cache_flush_events (TrackerNotifierEventCache *cache)
        cache->first = g_sequence_get_begin_iter (cache->sequence);
 
        g_async_queue_lock (priv->queue);
-       if (priv->querying) {
+       if (priv->urn_query_disabled) {
+               tracker_notifier_emit_events_in_idle (cache);
+       } else if (priv->querying) {
                g_async_queue_push_unlocked (priv->queue, cache);
        } else {
                priv->querying = TRUE;
@@ -946,3 +949,12 @@ tracker_notifier_event_get_urn (TrackerNotifierEvent *event)
        g_return_val_if_fail (event != NULL, NULL);
        return event->urn;
 }
+
+void
+tracker_notifier_disable_urn_query (TrackerNotifier *notifier)
+{
+       TrackerNotifierPrivate *priv;
+
+       priv = tracker_notifier_get_instance_private (notifier);
+       priv->urn_query_disabled = TRUE;
+}