[tracker] libtracker-data: Add support for the SUBSTR() builtin function

[Carlos Garnacho <carlosg src gnome org>]

commit 2db10ac9844b3d90ec3d9a1709929a653efb28f2
Author: Carlos Garnacho <carlosg gnome org>
Date:   Tue Jul 28 20:29:39 2015 +0200

    libtracker-data: Add support for the SUBSTR() builtin function
    
    This function is defined in Sparql 1.1 query language recommedation,
    http://www.w3.org/TR/sparql11-query/#func-substr

 src/libtracker-data/tracker-sparql-expression.vala |    6 ++++++
 src/libtracker-data/tracker-sparql-scanner.vala    |    6 ++++++
 2 files changed, 12 insertions(+), 0 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql-expression.vala 
b/src/libtracker-data/tracker-sparql-expression.vala
index 44dfe30..bb31628 100644
--- a/src/libtracker-data/tracker-sparql-expression.vala
+++ b/src/libtracker-data/tracker-sparql-expression.vala
@@ -1230,6 +1230,12 @@ class Tracker.Sparql.Expression : Object {
                        type = translate_aggregate_expression (sql);
                        sql.append (")");
                        return PropertyType.INTEGER;
+               case SparqlTokenType.SUBSTR:
+                       next ();
+                       expect (SparqlTokenType.OPEN_PARENS);
+                       var result = translate_function (sql, FN_NS + "substring");
+                       expect (SparqlTokenType.CLOSE_PARENS);
+                       return result;
                case SparqlTokenType.REGEX:
                        translate_regex (sql);
                        query.no_cache = true;
diff --git a/src/libtracker-data/tracker-sparql-scanner.vala b/src/libtracker-data/tracker-sparql-scanner.vala
index a1454aa..903de58 100644
--- a/src/libtracker-data/tracker-sparql-scanner.vala
+++ b/src/libtracker-data/tracker-sparql-scanner.vala
@@ -321,6 +321,10 @@ public class Tracker.SparqlScanner : Object {
                                case 't':
                                        if (matches (begin, "STRLEN")) return SparqlTokenType.STRLEN;
                                        break;
+                               case 'U':
+                               case 'u':
+                                       if (matches (begin, "SUBSTR")) return SparqlTokenType.SUBSTR;
+                                       break;
                                }
                                break;
                        }
@@ -986,6 +990,7 @@ public enum Tracker.SparqlTokenType {
        STRING_LITERAL_LONG1,
        STRING_LITERAL_LONG2,
        STRLEN,
+       SUBSTR,
        SUM,
        TRUE,
        UCASE,
@@ -1087,6 +1092,7 @@ public enum Tracker.SparqlTokenType {
                case STRING_LITERAL_LONG1: return "string literal";
                case STRING_LITERAL_LONG2: return "string literal";
                case STRLEN: return "`STRLEN'";
+               case SUBSTR: return "`SUBSTR'";
                case SUM: return "`SUM'";
                case TRUE: return "`true'";
                case UCASE: return "`UCASE'";