[tracker/wip/carlosg/serialize-api: 18/36] libtracker-sparql: Implement statement serialization on remote connections

[Carlos Garnacho <carlosg src gnome org>]

commit 84d39310253f11331f4e1dfc53399a4cdd1477f3
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sat Nov 27 14:55:26 2021 +0100

    libtracker-sparql: Implement statement serialization on remote connections
    
    These do also work via query rewriting, and asking the endpoint to give us
    RDF in the specified format.

 .../remote/tracker-remote-statement.c              | 64 ++++++++++++++++++++++
 1 file changed, 64 insertions(+)
---
diff --git a/src/libtracker-sparql/remote/tracker-remote-statement.c 
b/src/libtracker-sparql/remote/tracker-remote-statement.c
index 678394d7a..487f88967 100644
--- a/src/libtracker-sparql/remote/tracker-remote-statement.c
+++ b/src/libtracker-sparql/remote/tracker-remote-statement.c
@@ -369,6 +369,68 @@ tracker_remote_statement_clear_bindings (TrackerSparqlStatement *stmt)
        g_hash_table_remove_all (remote_stmt->bindings);
 }
 
+static void
+serialize_cb (GObject      *source,
+              GAsyncResult *res,
+              gpointer      user_data)
+{
+       GInputStream *istream;
+       GError *error = NULL;
+       GTask *task = user_data;
+
+       istream = tracker_sparql_connection_serialize_finish (TRACKER_SPARQL_CONNECTION (source),
+                                                             res, &error);
+       if (error)
+               g_task_return_error (task, error);
+       else
+               g_task_return_pointer (task, istream, g_object_unref);
+
+       g_object_unref (task);
+}
+
+static void
+tracker_remote_statement_serialize_async (TrackerSparqlStatement *stmt,
+                                          TrackerRdfFormat        format,
+                                          GCancellable           *cancellable,
+                                          GAsyncReadyCallback     callback,
+                                          gpointer                user_data)
+{
+       TrackerRemoteStatement *remote_stmt = TRACKER_REMOTE_STATEMENT (stmt);
+       gchar *rewritten_query = NULL;
+       GError *error = NULL;
+       GTask *task;
+
+       task = g_task_new (stmt, cancellable, callback, user_data);
+
+       if (g_hash_table_size (remote_stmt->bindings) > 0) {
+               rewritten_query = apply_bindings (stmt,
+                                                 remote_stmt->bindings,
+                                                 &error);
+               if (!rewritten_query) {
+                       g_task_return_error (task, error);
+                       g_object_unref (task);
+                       return;
+               }
+       }
+
+       tracker_sparql_connection_serialize_async (tracker_sparql_statement_get_connection (stmt),
+                                                  format,
+                                                  rewritten_query ? rewritten_query :
+                                                  tracker_sparql_statement_get_sparql (stmt),
+                                                  cancellable,
+                                                  serialize_cb,
+                                                  task);
+       g_free (rewritten_query);
+}
+
+static GInputStream *
+tracker_remote_statement_serialize_finish (TrackerSparqlStatement  *stmt,
+                                           GAsyncResult            *res,
+                                           GError                 **error)
+{
+       return g_task_propagate_pointer (G_TASK (res), error);
+}
+
 static void
 tracker_remote_statement_class_init (TrackerRemoteStatementClass *klass)
 {
@@ -386,6 +448,8 @@ tracker_remote_statement_class_init (TrackerRemoteStatementClass *klass)
        stmt_class->execute_async = tracker_remote_statement_execute_async;
        stmt_class->execute_finish = tracker_remote_statement_execute_finish;
        stmt_class->clear_bindings = tracker_remote_statement_clear_bindings;
+       stmt_class->serialize_async = tracker_remote_statement_serialize_async;
+       stmt_class->serialize_finish = tracker_remote_statement_serialize_finish;
 }
 
 static void