Ticket #350: Add-set_max_wildcard_expansion-method-to-the-queryparser-updated.patch

docs/queryparser.html

@@ -117 +117 @@
 to enable it, and tell the QueryParser which database to expand wildcards from
 using the <code>QueryParser::set_database(<i>database</i>)</code> method.
 
+<P>You can limit the number of terms a wildcard will expand to by
+calling <code>Xapian::QueryParser::set_max_wildcard_expansion()</code>. If a
+wildcard expands to more terms than that number, an exception will be
+thrown. The exception may be thrown by the QueryParser, or later when
+Enquire handles the query. The default is not to limit the expansion.
+
 <H3>Partially entered query matching</H3>
 
 <P>

include/xapian/queryparser.h

@@ -446 +446 @@
      */
     void set_database(const Database &db);
 
+    /** Specify the maximum expansion of a wildcard term.
+     *
+     *  Note: you must also set FLAG_WILDCARD for wildcard expansion to happen.
+     *
+     *  @param limit    The maximum number of terms each wildcard in the query
+     *                  can expand to, or 0 for no limit.
+     */
+    void set_max_wildcard_expansion(Xapian::termcount limit);
+
     /** Parse a query.
      *
      *  @param query_string  A free-text query as entered by a user

queryparser/queryparser.lemony

@@ -26 +26 @@
 #include "queryparser_internal.h"
 #include <xapian/error.h>
 #include <xapian/unicode.h>
+#include "str.h"
 #include "stringutils.h"
 
 // Include the list of token values lemon generates.
@@ -257 +258 @@
     void stoplist_resize(size_t s) {
         qpi->stoplist.resize(s);
     }
+
+    Xapian::termcount get_max_wildcard_expansion() const {
+        return qpi->max_wildcard_expansion;
+    }
 };
 
 string
@@ -370 +375 @@
 
     const list<string> & prefixes = prefix_info->prefixes;
     list<string>::const_iterator piter;
+    Xapian::termcount expansion_count = 0;
+    Xapian::termcount max = state_->get_max_wildcard_expansion();
     for (piter = prefixes.begin(); piter != prefixes.end(); ++piter) {
         string root = *piter;
         root += name;
         TermIterator t = db.allterms_begin(root);
         while (t != db.allterms_end(root)) {
+            if (max != 0 && ++expansion_count > max) {
+                string msg("Wilcard ");
+                msg += unstemmed;
+                msg += "* expands to more than ";
+                msg += str(max);
+                msg += " terms";
+                throw Xapian::QueryParserError(msg);
+            }
             subqs.push_back(Query(*t, 1, pos));
             ++t;
         }

queryparser/queryparser_internal.h

@@ -76 +76 @@
 
     string corrected_query;
 
+    Xapian::termcount max_wildcard_expansion;
+
     void add_prefix(const string &field, const string &prefix,
                     filter_type type);
 
@@ -84 +86 @@
 
   public:
     Internal() : stem_action(STEM_NONE), stopper(NULL),
-        default_op(Query::OP_OR), errmsg(NULL) { }
+        default_op(Query::OP_OR), errmsg(NULL), max_wildcard_expansion(0) { }
     Query parse_query(const string & query_string, unsigned int flags, const string & default_prefix);
 };
 

queryparser/queryparser.cc

@@ -103 +103 @@
     internal->db = db;
 }
 
+void
+QueryParser::set_max_wildcard_expansion(Xapian::termcount max)
+{
+    internal->max_wildcard_expansion = max;
+}
+
 Query
 QueryParser::parse_query(const string &query_string, unsigned flags,
                          const string &default_prefix)