[tracker] tracker-extract: Use safer method to insert tags in TIFF module

[Carlos Garnacho <carlosg src gnome org>]

commit 628bcfe33c7694dced142b50dd913defa78ed648
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Mar 14 12:45:52 2016 +0100

    tracker-extract: Use safer method to insert tags in TIFF module
    
    The current way of inserting the nao:hasTag relationship on the
    extracted file involves one join operation per tag being inserted.
    This has performance implications, plus we can feasibly hit the
    sqlite limit of 64 tables in joins.
    
    Instead insert the tags in separate inserts, that will be as fast
    as it gets, plus there's no limit in the number of tags.

 src/tracker-extract/tracker-extract-tiff.c |   60 ++++++++++++----------------
 1 files changed, 26 insertions(+), 34 deletions(-)
---
diff --git a/src/tracker-extract/tracker-extract-tiff.c b/src/tracker-extract/tracker-extract-tiff.c
index 52ca512..d14ac79 100644
--- a/src/tracker-extract/tracker-extract-tiff.c
+++ b/src/tracker-extract/tracker-extract-tiff.c
@@ -266,8 +266,7 @@ tracker_extract_get_metadata (TrackerExtractInfo *info)
        guint i;
        GFile *file;
        TrackerSparqlBuilder *metadata, *preupdate;
-       const gchar *graph;
-       GString *where;
+       const gchar *graph, *urn;
        int fd;
 
 #ifdef HAVE_LIBIPTCDATA
@@ -286,6 +285,7 @@ tracker_extract_get_metadata (TrackerExtractInfo *info)
        preupdate = tracker_extract_info_get_preupdate_builder (info);
        metadata = tracker_extract_info_get_metadata_builder (info);
        graph = tracker_extract_info_get_graph (info);
+       urn = tracker_extract_info_get_urn (info);
 
        fd = tracker_file_open_fd (filename);
 
@@ -407,7 +407,7 @@ tracker_extract_get_metadata (TrackerExtractInfo *info)
        md.make = tracker_coalesce_strip (3, xd->make, td.make, ed->make);
        md.model = tracker_coalesce_strip (3, xd->model, td.model, ed->model);
 
-       keywords = g_ptr_array_new ();
+       keywords = g_ptr_array_new_with_free_func ((GDestroyNotify) g_free);
 
        if (ed->user_comment) {
                tracker_sparql_builder_predicate (metadata, "nie:comment");
@@ -615,34 +615,22 @@ tracker_extract_get_metadata (TrackerExtractInfo *info)
                tracker_keywords_parse (keywords, id->keywords);
        }
 
-       where = g_string_new ("");
-
        for (i = 0; i < keywords->len; i++) {
-               gchar *p, *escaped, *var;
+               gchar *escaped, *subject;
+               const gchar *p;
 
                p = g_ptr_array_index (keywords, i);
                escaped = tracker_sparql_escape_string (p);
-               var = g_strdup_printf ("tag%d", i + 1);
+               subject = g_strdup_printf ("_:tag%d", i + 1);
 
                /* ensure tag with specified label exists */
-               tracker_sparql_builder_append (preupdate, "INSERT { ");
-
-               if (graph) {
-                       tracker_sparql_builder_append (preupdate, "GRAPH <");
-                       tracker_sparql_builder_append (preupdate, graph);
-                       tracker_sparql_builder_append (preupdate, "> { ");
-               }
-
-               tracker_sparql_builder_append (preupdate,
-                                              "_:tag a nao:Tag ; nao:prefLabel \"");
-               tracker_sparql_builder_append (preupdate, escaped);
-               tracker_sparql_builder_append (preupdate, "\"");
-
-               if (graph) {
-                       tracker_sparql_builder_append (preupdate, " } ");
-               }
-
-               tracker_sparql_builder_append (preupdate, " }\n");
+               tracker_sparql_builder_insert_open (preupdate, graph);
+               tracker_sparql_builder_subject (preupdate, subject);
+               tracker_sparql_builder_predicate (preupdate, "a");
+               tracker_sparql_builder_object (preupdate, "nao:Tag");
+               tracker_sparql_builder_predicate (preupdate, "nao:prefLabel");
+               tracker_sparql_builder_object_unvalidated (preupdate, escaped);
+               tracker_sparql_builder_insert_close (preupdate);
                tracker_sparql_builder_append (preupdate,
                                               "WHERE { FILTER (NOT EXISTS { "
                                               "?tag a nao:Tag ; nao:prefLabel \"");
@@ -651,20 +639,24 @@ tracker_extract_get_metadata (TrackerExtractInfo *info)
                                               "\" }) }\n");
 
                /* associate file with tag */
-               tracker_sparql_builder_predicate (metadata, "nao:hasTag");
-               tracker_sparql_builder_object_variable (metadata, var);
-
-               g_string_append_printf (where, "?%s a nao:Tag ; nao:prefLabel \"%s\" .\n", var, escaped);
+               tracker_sparql_builder_insert_open (preupdate, graph);
+               tracker_sparql_builder_subject_iri (preupdate, urn);
+               tracker_sparql_builder_predicate (preupdate, "nao:hasTag");
+               tracker_sparql_builder_object (preupdate, "?tag");
+               tracker_sparql_builder_insert_close (preupdate);
+               tracker_sparql_builder_where_open (preupdate);
+               tracker_sparql_builder_subject (preupdate, "?tag");
+               tracker_sparql_builder_predicate (preupdate, "a");
+               tracker_sparql_builder_object (preupdate, "nao:Tag");
+               tracker_sparql_builder_predicate (preupdate, "nao:prefLabel");
+               tracker_sparql_builder_object_unvalidated (preupdate, escaped);
+               tracker_sparql_builder_where_close (preupdate);
 
-               g_free (var);
+               g_free (subject);
                g_free (escaped);
-               g_free (p);
        }
        g_ptr_array_free (keywords, TRUE);
 
-       tracker_extract_info_set_where_clause (info, where->str);
-       g_string_free (where, TRUE);
-
        if (md.make || md.model) {
                gchar *equip_uri;