[tracker/tracker-0.10] SPARQL: Ensure that WHERE clause is evaluated before performing updates

[Martyn James Russell <mr src gnome org>]

commit 34b06b7a7b00fb3d8695b4f173277f48f9b41941
Author: JÃrg Billeter <j bitron ch>
Date:   Mon Aug 22 16:00:50 2011 +0200

    SPARQL: Ensure that WHERE clause is evaluated before performing updates
    
    This will increase peak memory usage for updates with a WHERE clause
    that returns many solutions.
    
    Fixes NB#242979.

 src/libtracker-data/tracker-sparql-query.vala |   21 ++++++++++++++-------
 1 files changed, 14 insertions(+), 7 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql-query.vala b/src/libtracker-data/tracker-sparql-query.vala
index 056719e..171922b 100644
--- a/src/libtracker-data/tracker-sparql-query.vala
+++ b/src/libtracker-data/tracker-sparql-query.vala
@@ -688,24 +688,31 @@ public class Tracker.Sparql.Query : Object {
 		this.delete_statements = delete_statements;
 		this.update_statements = update_statements;
 
-		// iterate over all solutions
-		while (cursor.next ()) {
-			// blank nodes in construct templates are per solution
-
-			uuid_generate (base_uuid);
-			blank_nodes = new HashTable<string,string>.full (str_hash, str_equal, g_free, g_free);
+		var solutions = new GenericArray<HashTable<string,string>> ();
 
+		while (cursor.next ()) {
 			// get values of all variables to be bound
 			var var_value_map = new HashTable<string,string>.full (str_hash, str_equal, g_free, g_free);
 			int var_idx = 0;
 			foreach (var variable in context.var_set.get_keys ()) {
 				var_value_map.insert (variable.name, cursor.get_string (var_idx++));
 			}
+			solutions.add (var_value_map);
+		}
+
+		cursor = null;
+
+		// iterate over all solutions
+		for (int i = 0; i < solutions.length; i++) {
+			// blank nodes in construct templates are per solution
+
+			uuid_generate (base_uuid);
+			blank_nodes = new HashTable<string,string>.full (str_hash, str_equal, g_free, g_free);
 
 			set_location (template_location);
 
 			// iterate over each triple in the template
-			parse_construct_triples_block (var_value_map);
+			parse_construct_triples_block (solutions[i]);
 
 			if (blank && update_blank_nodes != null) {
 				update_blank_nodes.add_value (blank_nodes);