[tracker] SPARQL: Fix generated SQL when not retrieving actual data

[Jürg Billeter <juergbi src gnome org>]

commit 5a06e9ef2f290a78a4dc92e413f0364357325cde
Author: Jürg Billeter <j bitron ch>
Date:   Mon Jul 12 12:27:35 2010 +0200

    SPARQL: Fix generated SQL when not retrieving actual data

 src/libtracker-data/tracker-sparql-pattern.vala |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql-pattern.vala b/src/libtracker-data/tracker-sparql-pattern.vala
index c2b51e5..432b174 100644
--- a/src/libtracker-data/tracker-sparql-pattern.vala
+++ b/src/libtracker-data/tracker-sparql-pattern.vala
@@ -1203,6 +1203,8 @@ class Tracker.Sparql.Pattern : Object {
 	}
 
 	void parse_object (StringBuilder sql, bool in_simple_optional = false) throws SparqlError {
+		long begin_sql_len = sql.len;
+
 		bool object_is_var;
 		string object = parse_var_or_term (sql, out object_is_var);
 
@@ -1481,10 +1483,9 @@ class Tracker.Sparql.Pattern : Object {
 			}
 		}
 
-		if (!current_subject_is_var &&
-		    !current_predicate_is_var &&
-		    !object_is_var) {
-			// no variables involved, add dummy expression to SQL
+		if (sql.len == begin_sql_len) {
+			// no SELECT expression was added, add dummy expression
+			// this is required in cases where no values need to be retrieved
 			sql.append ("1, ");
 		}
 	}