Index: mod/quiz/attemptlib.php
===================================================================
RCS file: /cvsroot/moodle/mod/quiz/attemptlib.php,v
retrieving revision 1.76
diff -u -r1.76 attemptlib.php
--- mod/quiz/attemptlib.php	16 Mar 2011 08:46:31 -0000	1.76
+++ mod/quiz/attemptlib.php	6 Apr 2011 07:17:15 -0000
@@ -103,6 +103,17 @@
         if (!$quiz = $DB->get_record('quiz', array('id' => $quizid))) {
             throw new moodle_exception('invalidquizid', 'quiz');
         }
+
+        /// Get previous attempts of this user
+        /// And also we will need 'uniqueid's of all previous attempts to avoid using one question twice
+        $previousattempts = array_keys($DB->get_records_select('quiz_attempts', "quiz = '$quizid' AND " .
+                "userid = '$userid' AND timefinish > 0 AND preview != 1", null, '', 'uniqueid'));
+        $numberofpreviousattempts = count($previousattempts);
+
+        // MDL-6340: random question should know old attempts of this user to avoid using one question twice
+        $previousattemptslist = implode(',', $previousattempts);
+        $quiz->previousattempts = $previousattemptslist;
+
         if (!$course = $DB->get_record('course', array('id' => $quiz->course))) {
             throw new moodle_exception('invalidcoursemodule');
         }
Index: question/type/random/questiontype.php
===================================================================
RCS file: /cvsroot/moodle/question/type/random/questiontype.php,v
retrieving revision 1.42
diff -u -r1.42 questiontype.php
--- question/type/random/questiontype.php	9 Mar 2011 08:20:43 -0000	1.42
+++ question/type/random/questiontype.php	6 Apr 2011 07:20:10 -0000
@@ -148,9 +148,10 @@
      * @param integer $categoryid the id of a question category.
      * @param boolean whether to include questions from subcategories.
      * @param string $questionsinuse comma-separated list of question ids to exclude from consideration.
-     * @return array of question records.
+     * @param string $avoidquestionsfromattempts comma-separated list of attempt ids of this user.
+     * @return array of question ids with less used questions placed last.
      */
-    function get_usable_questions_from_category($categoryid, $subcategories, $questionsinuse) {
+    function get_usable_questions_from_category($categoryid, $subcategories, $questionsinuse, $avoidquestionsfromattempts) {
         global $DB;
         $this->init_qtype_lists();
         if ($subcategories) {
@@ -158,15 +159,48 @@
         } else {
             $categorylist = $categoryid;
         }
-        if (!$catrandoms = $DB->get_records_select('question',
-                "category IN ($categorylist)
-                     AND parent = 0
-                     AND hidden = 0
-                     AND id NOT IN ($questionsinuse)
-                     AND qtype NOT IN ($this->excludedqtypes)", null, '', 'id')) {
-            $catrandoms = array();
+
+        if($avoidquestionsfromattempts === ''){
+            /// If this is first attempt for this user we simply get all question id's
+            /// that can be used in this random
+            if (!$catrandoms = $DB->get_records_select('question',
+                 "category IN ($categorylist)
+                      AND parent = 0
+                      AND hidden = 0
+                      AND id NOT IN ($questionsinuse)
+                      AND qtype NOT IN ($this->excludedqtypes)", null, '', 'id')) {
+                $catrandoms = array();
+            }
+            return swapshuffle(array_keys($catrandoms));
+        } else {
+            /// Get list of usable questions with question id's as keys and 
+            ///     number of previous uses by this user as value
+                list($sqlcategorylist,$paramscategorylist) = $DB->get_in_or_equal($categorylist);
+                list($sqlquestionsinuse,$paramsquestionsinuse) = $DB->get_in_or_equal($questionsinuse, SQL_PARAMS_QM, 'param0000', false);
+                list($sqlexcludedqtypes,$paramsexcludedqtypes) = $DB->get_in_or_equal($this->excludedqtypes, SQL_PARAMS_QM, 'param0000', false);
+                list($sqlavoidquestionsfromattempts,$paramsavoidquestionsfromattempts) = $DB->get_in_or_equal($avoidquestionsfromattempts);
+                $previoususes = $DB->get_records_sql("SELECT q.id, COUNT(qst.id) AS numprevioususes
+                FROM {question} q
+                LEFT JOIN {question_states} qst ON qst.answer LIKE CONCAT('random', q.id, '-%')
+                WHERE q.category $sqlcategorylist
+                    AND q.parent = 0
+                    AND q.hidden = 0
+                    AND q.id $sqlquestionsinuse
+                    AND q.qtype $sqlexcludedqtypes
+                    AND ((qst.attempt IS NULL) OR (qst.attempt $sqlavoidquestionsfromattempts))
+                    AND ((qst.seq_number IS NULL) OR (qst.seq_number = 0))
+                GROUP BY q.id
+                ORDER BY numprevioususes ASC", array_merge($paramscategorylist, $paramsquestionsinuse, $paramsexcludedqtypes, $paramsavoidquestionsfromattempts));
+            /// Since no question can be used twice in one attempt and we are trying hard to use 
+            ///    less used questions first there should be at most two subsequent numbers of previous uses.
+            $minusedcount = current($previoususes);
+            $minused = array_keys($previoususes, $minusedcount);
+            $maxused = array_keys($previoususes, $minusedcount + 1);
+
+            /// Now we should reshuffle questions with each number of uses separately and merge them 
+            ///    in array of question ids  placing less used questions last.
+            return array_merge(swapshuffle($maxused), swapshuffle($minused));
         }
-        return $catrandoms;
     }
 
     function create_session_and_responses(&$question, &$state, $cmoptions, $attempt) {
@@ -184,16 +218,16 @@
 
         if (!isset($this->catrandoms[$question->category][$question->questiontext])) {
             $catrandoms = $this->get_usable_questions_from_category($question->category,
-                    $question->questiontext == "1", $cmoptions->questionsinuse);
-            $this->catrandoms[$question->category][$question->questiontext] = swapshuffle_assoc($catrandoms);
+                    $question->questiontext == "1", $cmoptions->questionsinuse, $cmoptions->previousattempts);
+            $this->catrandoms[$question->category][$question->questiontext] = $catrandoms;
         }
 
         while ($wrappedquestion = array_pop(
                 $this->catrandoms[$question->category][$question->questiontext])) {
-            if (!preg_match("~(^|,)$wrappedquestion->id(,|$)~", $cmoptions->questionsinuse)) {
+            if (!strpos(','.$cmoptions->questionsinuse.',', ','.$wrappedquestion.',')) {
                 /// $randomquestion is not in use and will therefore be used
                 /// as the randomquestion here...
-                $wrappedquestion = $DB->get_record('question', array('id' => $wrappedquestion->id));
+                $wrappedquestion = $DB->get_record('question', array('id' => $wrappedquestion));
                 global $QTYPES;
                 $QTYPES[$wrappedquestion->qtype]
                         ->get_question_options($wrappedquestion);