GUI: only do the result up to date check before preview for the main index (we cant update the others anyway)

src/rcldb/rcldb.cpp

@@ -841,6 +841,16 @@ bool Db::rmQueryDb(const string &dir)
     return adjustdbs();
 }
 
+// Determining what index a doc result comes from is based on the
+// modulo of the docid against the db count. Ref:
+// http://trac.xapian.org/wiki/FAQ/MultiDatabaseDocumentID
+size_t Db::whatDbIdx(const Doc& doc)
+{
+    if (doc.xdocid == 0) 
+	return (size_t)-1;
+    return doc.xdocid % m_extraDbs.size();
+}
+
 bool Db::testDbDir(const string &dir)
 {
     string aerr;

src/rcldb/rcldb.h

@@ -197,6 +197,11 @@ class Db {
     bool addQueryDb(const string &dir);
     /** Remove extra database. if dir == "", remove all. */
     bool rmQueryDb(const string &dir);
+    /** Look where the doc result comes from. 
+     * @return: 0 main index, (size_t)-1 don't know, 
+     *   other: order of database in add_database() sequence.
+     */
+    size_t whatDbIdx(const Doc& doc);
     /** Tell if directory seems to hold xapian db */
     static bool testDbDir(const string &dir);