[tracker] SPARQL: Do not leak variables (reference cycle)

[Jürg Billeter <juergbi src gnome org>]

commit 01be5f7422cdfa82af10b4f4400e4ac27a6a993d
Author: Jürg Billeter <j bitron ch>
Date:   Tue Oct 27 14:55:36 2009 +0100

    SPARQL: Do not leak variables (reference cycle)

 src/libtracker-data/tracker-sparql-query.vala |   12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql-query.vala b/src/libtracker-data/tracker-sparql-query.vala
index 65e5d7a..bbe0f98 100644
--- a/src/libtracker-data/tracker-sparql-query.vala
+++ b/src/libtracker-data/tracker-sparql-query.vala
@@ -58,7 +58,7 @@ public class Tracker.SparqlQuery : Object {
 
 	// Represents a mapping of a SPARQL variable to a SQL table and column
 	class VariableBinding : DataBinding {
-		public Variable variable;
+		public weak Variable variable;
 		// Specified whether SQL column may contain NULL entries
 		public bool maybe_null;
 		public bool in_simple_optional;
@@ -379,8 +379,8 @@ public class Tracker.SparqlQuery : Object {
 		return "'%s'".printf (string.joinv ("''", literal.split ("'")));
 	}
 
-	Variable get_variable (string name) {
-		var result = var_map.lookup (name);
+	unowned Variable get_variable (string name) {
+		unowned Variable result = var_map.lookup (name);
 		if (result == null) {
 			// use lowercase as SQLite is never case sensitive (not conforming to SQL)
 			string sql_identifier = "%s_u".printf (name).down ();
@@ -392,8 +392,10 @@ public class Tracker.SparqlQuery : Object {
 			}
 			used_sql_identifiers.insert (sql_identifier, true);
 
-			result = new Variable (name, sql_identifier);
-			var_map.insert (name, result);
+			var variable = new Variable (name, sql_identifier);
+			var_map.insert (name, variable);
+
+			result = variable;
 		}
 		return result;
 	}