[tracker/wip/carlosg/bindings-in-service: 2/6] libtracker-sparql: Refactor service graph pattern variable extraction

[Carlos Garnacho <carlosg src gnome org>]

commit 3ffeefb4387a52e833cc1a54f974a16d2a457fff
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon May 4 01:26:27 2020 +0200

    libtracker-sparql: Refactor service graph pattern variable extraction
    
    Move it to a separate function.

 src/libtracker-data/tracker-sparql.c | 54 +++++++++++++++++++++++++-----------
 1 file changed, 38 insertions(+), 16 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql.c b/src/libtracker-data/tracker-sparql.c
index 111306033..c16c3a19b 100644
--- a/src/libtracker-data/tracker-sparql.c
+++ b/src/libtracker-data/tracker-sparql.c
@@ -4588,15 +4588,47 @@ translate_GraphGraphPattern (TrackerSparql  *sparql,
        return TRUE;
 }
 
+static GList *
+extract_variables (TrackerSparql     *sparql,
+                   TrackerParserNode *pattern)
+{
+       TrackerParserNode *node;
+       GList *variables = NULL;
+
+       for (node = tracker_sparql_parser_tree_find_first (pattern, TRUE);
+            node;
+            node = tracker_sparql_parser_tree_find_next (node, TRUE)) {
+               const TrackerGrammarRule *rule;
+
+               if (!g_node_is_ancestor ((GNode *) pattern, (GNode *) node))
+                       break;
+
+               rule = tracker_parser_node_get_rule (node);
+
+               if (!tracker_grammar_rule_is_a (rule, RULE_TYPE_TERMINAL,
+                                               TERMINAL_TYPE_VAR1) &&
+                   !tracker_grammar_rule_is_a (rule, RULE_TYPE_TERMINAL,
+                                               TERMINAL_TYPE_VAR2) &&
+                   !tracker_grammar_rule_is_a (rule, RULE_TYPE_TERMINAL,
+                                               TERMINAL_TYPE_PARAMETERIZED_VAR))
+                       continue;
+
+               variables = g_list_prepend (variables, node);
+       }
+
+       return variables;
+}
+
 static gboolean
 translate_ServiceGraphPattern (TrackerSparql  *sparql,
                                GError        **error)
 {
        gssize pattern_start, pattern_end;
-       TrackerParserNode *pattern, *node;
+       TrackerParserNode *pattern;
        gchar *pattern_str, *escaped_str, *var_str;
        TrackerContext *context;
        GList *variables = NULL;
+       GList *variable_rules = NULL, *l;
        TrackerToken service;
        GString *service_sparql;
        gboolean silent = FALSE, do_join;
@@ -4626,24 +4658,13 @@ translate_ServiceGraphPattern (TrackerSparql  *sparql,
        _append_string (sparql, "SELECT ");
        service_sparql = g_string_new ("SELECT ");
 
-       for (node = tracker_sparql_parser_tree_find_first (pattern, TRUE);
-            node;
-            node = tracker_sparql_parser_tree_find_next (node, TRUE)) {
-               const TrackerGrammarRule *rule;
+       variable_rules = extract_variables (sparql, pattern);
+
+       for (l = variable_rules; l; l = l->next) {
+               TrackerParserNode *node = l->data;
                TrackerBinding *binding;
                TrackerVariable *var;
 
-               if (!g_node_is_ancestor ((GNode *) pattern, (GNode *) node))
-                       break;
-
-               rule = tracker_parser_node_get_rule (node);
-
-               if (!tracker_grammar_rule_is_a (rule, RULE_TYPE_TERMINAL,
-                                               TERMINAL_TYPE_VAR1) &&
-                   !tracker_grammar_rule_is_a (rule, RULE_TYPE_TERMINAL,
-                                               TERMINAL_TYPE_VAR2))
-                       continue;
-
                if (i > 0)
                        _append_string (sparql, ", ");
 
@@ -4676,6 +4697,7 @@ translate_ServiceGraphPattern (TrackerSparql  *sparql,
        tracker_token_unset (&service);
        tracker_sparql_pop_context (sparql, TRUE);
        g_string_free (service_sparql, TRUE);
+       g_list_free (variable_rules);
 
        if (do_join)
                _append_string (sparql, ") ");