[tracker: 6/9] libtracker-data: Resolve variables looking up the binding if we're in same context

[Carlos Garnacho <carlosg src gnome org>]

commit 64b54a7784180f92635df537667e57ec96e0552b
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Oct 18 22:04:21 2015 +0200

    libtracker-data: Resolve variables looking up the binding if we're in same context
    
    This is necessary for BIND support, as the variables looked up to add the
    BIND alias likely belong to the same scope that we're currently building.
    This results in SQL like (very simplified, and shortened):
    
      SELECT "nie:url" AS "1_u", "1_u" AS "2_u" ...
    
    The second "1_u" can't be looked up yet in this scope (only on the WHERE
    clause, or a wrapping SELECT), so ends up as the string itself. With this
    change, this kind of queries will result in (shortened again):
    
      SELECT "nie:url" AS "1_u", "nie:url" AS "2_u" ...
    
    Which is legal, and results in the expected values assigned to the BIND
    alias.

 src/libtracker-data/tracker-sparql-expression.vala |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql-expression.vala 
b/src/libtracker-data/tracker-sparql-expression.vala
index c6062b8..d69b908 100644
--- a/src/libtracker-data/tracker-sparql-expression.vala
+++ b/src/libtracker-data/tracker-sparql-expression.vala
@@ -1142,7 +1142,12 @@ class Tracker.Sparql.Expression : Object {
                        next ();
                        string variable_name = get_last_string ().substring (1);
                        var variable = context.get_variable (variable_name);
-                       sql.append (variable.sql_expression);
+
+                       if (context == variable.origin_context && variable.binding != null) {
+                               sql.append (variable.binding.sql_expression);
+                       } else {
+                               sql.append (variable.sql_expression);
+                       }
 
                        if (variable.binding == null) {
                                return PropertyType.UNKNOWN;