[tracker] libtracker-data: Wrap BIND argument with () in SQL

[Carlos Garnacho <carlosg src gnome org>]

commit 8fc47cfed03030e5377bc7989e5afd24e9b24c5b
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Nov 21 13:24:42 2016 +0100

    libtracker-data: Wrap BIND argument with () in SQL
    
    Constructing the query as "SELECT $bind * FROM (...)" may trigger
    sqlite parser overflows if the BIND form turns out to be too complex,
    Doing the query as "SELECT ($bind) * FROM (...)" seems to be more
    friendly to the parser.
    
    This error was seen in gnome-music search, where the BIND() argument
    is something like:
    
    BIND((IF(STRSTARTS(?title_lower, "the "), SUBSTR(?title_lower, 5),
             IF(STRSTARTS(?title_lower, "a "), SUBSTR(?title_lower, 3),
                IF(STRSTARTS(?title_lower, "an "), SUBSTR(?title_lower, 4),
                   fn:replace(fn:lower-case(?title_lower),
                              "^[ !\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~]+|[ 
!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~]+$", "")
                  )
               )
            )
         ) AS ?title_collation)
    
    Which, despite the fn:replace regex argument being passed as a host
    parameter, seemed too much to sqlite.

 src/libtracker-data/tracker-sparql-pattern.vala |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql-pattern.vala b/src/libtracker-data/tracker-sparql-pattern.vala
index 6a67679..d37474b 100644
--- a/src/libtracker-data/tracker-sparql-pattern.vala
+++ b/src/libtracker-data/tracker-sparql-pattern.vala
@@ -1130,9 +1130,9 @@ class Tracker.Sparql.Pattern : Object {
                                if (in_group_graph_pattern) {
                                        // Surround the entire group graph pattern with
                                        // SELECT $binding , * FROM (...)
-                                       var binding_sql = new StringBuilder ("SELECT ");
+                                       var binding_sql = new StringBuilder ("SELECT (");
                                        add_variable_binding (binding_sql, binding, VariableState.BOUND);
-                                       binding_sql.append (" * FROM (");
+                                       binding_sql.append (") * FROM (");
                                        sql.insert (group_graph_pattern_start, binding_sql.str);
                                        sql.append (")");
                                } else {