[tracker/wip/garnacho/sparql1.1: 68/69] libtracker-data: Add support for BIND

[Carlos Garnacho <carlosg src gnome org>]

commit ca5d939fed4715398a8f424e746626e9905e04b6
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Oct 18 22:41:27 2015 +0200

    libtracker-data: Add support for BIND
    
    The BIND form allows a value to be assigned to a variable from a graph
    pattern:
    
      SELECT ?u ?hour
      { ?u a rdfs:Resource .
           nfo:fileLastModified ?modified
        BIND (HOUR (?modified) AS ?hour)
      }
    
    It will be specially useful on places where we use the result of a
    calculation on more than one places, eg. on SELECT and FILTER(). It will
    also be useful combined with DELETE...INSERT...WHERE to perform complex
    mass-updates in a single query.
    
    http://www.w3.org/TR/sparql11-query/#bind

 src/libtracker-data/tracker-sparql-pattern.vala |   22 ++++++++++++++++++++++
 src/libtracker-data/tracker-sparql-scanner.vala |   13 ++++++++++++-
 2 files changed, 34 insertions(+), 1 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql-pattern.vala b/src/libtracker-data/tracker-sparql-pattern.vala
index 7dfbcd4..ec9d547 100644
--- a/src/libtracker-data/tracker-sparql-pattern.vala
+++ b/src/libtracker-data/tracker-sparql-pattern.vala
@@ -1102,6 +1102,28 @@ class Tracker.Sparql.Pattern : Object {
 
                                current_graph = old_graph;
                                current_graph_is_var = old_graph_is_var;
+                       } else if (accept (SparqlTokenType.BIND)) {
+                               var binding = new VariableBinding ();
+                               var bind_sql = new StringBuilder ();
+
+                               expect (SparqlTokenType.OPEN_PARENS);
+
+                               expression.translate_expression (bind_sql);
+                               binding.sql_expression = bind_sql.str;
+
+                               expect (SparqlTokenType.AS);
+                               expect (SparqlTokenType.VAR);
+
+                               var as_var = context.get_variable (get_last_string ().substring (1));
+
+                               if (as_var.binding != null) {
+                                       throw query.get_internal_error ("Expected undefined variable in BIND 
alias");
+                               }
+
+                               binding.variable = as_var;
+                               add_variable_binding (sql, binding, VariableState.BOUND);
+
+                               expect (SparqlTokenType.CLOSE_PARENS);
                        } else if (current () == SparqlTokenType.OPEN_BRACE) {
                                if (!in_triples_block && !in_group_graph_pattern) {
                                        in_group_graph_pattern = true;
diff --git a/src/libtracker-data/tracker-sparql-scanner.vala b/src/libtracker-data/tracker-sparql-scanner.vala
index f23ba0a..e370560 100644
--- a/src/libtracker-data/tracker-sparql-scanner.vala
+++ b/src/libtracker-data/tracker-sparql-scanner.vala
@@ -159,7 +159,16 @@ public class Tracker.SparqlScanner : Object {
                        switch (begin[0]) {
                        case 'B':
                        case 'b':
-                               if (matches (begin, "BASE")) return SparqlTokenType.BASE;
+                               switch (begin[1]) {
+                               case 'A':
+                               case 'a':
+                                       if (matches (begin, "BASE")) return SparqlTokenType.BASE;
+                                       break;
+                               case 'I':
+                               case 'i':
+                                       if (matches (begin, "BIND")) return SparqlTokenType.BIND;
+                                       break;
+                               }
                                break;
                        case 'C':
                        case 'c':
@@ -1021,6 +1030,7 @@ public enum Tracker.SparqlTokenType {
        AVG,
        BASE,
        BLANK_NODE,
+       BIND,
        BOUND,
        BY,
        CEIL,
@@ -1148,6 +1158,7 @@ public enum Tracker.SparqlTokenType {
                case AVG: return "`AVG'";
                case BASE: return "`BASE'";
                case BLANK_NODE: return "blank node";
+               case BIND: return "`BIND'";
                case BOUND: return "`BOUND'";
                case BY: return "`BY'";
                case CEIL: return "`CEIL'";