diff --git a/question/engine/datalib.php b/question/engine/datalib.php
index 61910e8e01b..7e367039fbb 100644
--- a/question/engine/datalib.php
+++ b/question/engine/datalib.php
@@ -1076,6 +1076,20 @@ ORDER BY
      * @param number $newmaxmark the new max mark to set.
      */
     public function set_max_mark_in_attempts(qubaid_condition $qubaids, $slot, $newmaxmark) {
+        if ($this->db->get_dbfamily() == 'mysql') {
+            // MySQL's query optimiser completely fails to cope with the
+            // set_field_select call below, so we have to give it a clue. See MDL-32616.
+            // TODO MDL-29589 encapsulate this MySQL-specific code with a $DB method.
+            $this->db->execute("
+                    UPDATE " . $qubaids->from_question_attempts('qa') . "
+                       SET qa.maxmark = :newmaxmark
+                     WHERE " . $qubaids->where() . "
+                       AND slot = :slot
+                    ", $qubaids->from_where_params() + array('newmaxmark' => $newmaxmark, 'slot' => $slot));
+            return;
+        }
+
+        // Normal databases.
         $this->db->set_field_select('question_attempts', 'maxmark', $newmaxmark,
                 "questionusageid {$qubaids->usage_id_in()} AND slot = :slot",
                 $qubaids->usage_id_in_params() + array('slot' => $slot));
diff --git a/question/engine/tests/question_engine_data_mapper_test.php b/question/engine/tests/datalib_reporting_queries_test.php
similarity index 92%
rename from question/engine/tests/question_engine_data_mapper_test.php
rename to question/engine/tests/datalib_reporting_queries_test.php
index 932576c0396..5288fdba5fe 100644
--- a/question/engine/tests/question_engine_data_mapper_test.php
+++ b/question/engine/tests/datalib_reporting_queries_test.php
@@ -15,12 +15,12 @@
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
 /**
- * This file contains tests for the autosave code in the question_usage class.
+ * Unit tests for the parts of {@link question_engine_data_mapper} related to reporting.
  *
- * @package    moodlecore
- * @subpackage questionengine
- * @copyright  2013 The Open University
- * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ * @package   core_question
+ * @category  test
+ * @copyright 2013 The Open University
+ * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 
 
@@ -32,17 +32,12 @@ require_once(dirname(__FILE__) . '/helpers.php');
 
 
 /**
- * Unit tests for the autosave parts of the {@link question_usage} class.
- *
- * Note that many of the methods used when attempting questions, like
- * load_questions_usage_by_activity, insert_question_*, delete_steps are
- * tested elsewhere, e.g. by {@link question_usage_autosave_test}. We do not
- * re-test them here.
+ * Unit tests for the parts of {@link question_engine_data_mapper} related to reporting.
  *
  * @copyright 2013 The Open University
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
-class question_engine_data_mapper_testcase extends qbehaviour_walkthrough_test_base {
+class question_engine_data_mapper_reporting_testcase extends qbehaviour_walkthrough_test_base {
 
     /** @var question_engine_data_mapper */
     protected $dm;
@@ -132,6 +127,9 @@ class question_engine_data_mapper_testcase extends qbehaviour_walkthrough_test_b
         $this->dotest_question_attempt_latest_state_view();
     }
 
+    /**
+     * This test is executed by {@link test_reporting_queries()}.
+     */
     protected function dotest_load_questions_usages_latest_steps() {
         $rawstates = $this->dm->load_questions_usages_latest_steps($this->bothusages, $this->allslots,
                 'qa.id AS questionattemptid, qa.questionusageid, qa.slot, ' .
@@ -178,6 +176,9 @@ class question_engine_data_mapper_testcase extends qbehaviour_walkthrough_test_b
         ), $state);
     }
 
+    /**
+     * This test is executed by {@link test_reporting_queries()}.
+     */
     protected function dotest_load_questions_usages_question_state_summary() {
         $summary = $this->dm->load_questions_usages_question_state_summary(
                 $this->bothusages, $this->allslots);
@@ -206,6 +207,9 @@ class question_engine_data_mapper_testcase extends qbehaviour_walkthrough_test_b
                 ));
     }
 
+    /**
+     * This test is executed by {@link test_reporting_queries()}.
+     */
     protected function dotest_load_questions_usages_where_question_in_state() {
         $this->assertEquals(
                 array(array($this->usageids[0], $this->usageids[1]), 2),
@@ -223,6 +227,9 @@ class question_engine_data_mapper_testcase extends qbehaviour_walkthrough_test_b
                 'needsgrading', $this->allslots[1], null, 'questionusageid'));
     }
 
+    /**
+     * This test is executed by {@link test_reporting_queries()}.
+     */
     protected function dotest_load_average_marks() {
         $averages = $this->dm->load_average_marks($this->bothusages);
 
@@ -240,6 +247,9 @@ class question_engine_data_mapper_testcase extends qbehaviour_walkthrough_test_b
         ), $averages);
     }
 
+    /**
+     * This test is executed by {@link test_reporting_queries()}.
+     */
     protected function dotest_sum_usage_marks_subquery() {
         global $DB;
 
@@ -253,6 +263,9 @@ class question_engine_data_mapper_testcase extends qbehaviour_walkthrough_test_b
         $this->assertEquals(0, $totals[$this->usageids[1]]);
     }
 
+    /**
+     * This test is executed by {@link test_reporting_queries()}.
+     */
     protected function dotest_question_attempt_latest_state_view() {
         global $DB;
 
diff --git a/question/engine/tests/datalib_test.php b/question/engine/tests/datalib_test.php
new file mode 100644
index 00000000000..9279626be67
--- /dev/null
+++ b/question/engine/tests/datalib_test.php
@@ -0,0 +1,129 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Unit tests for parts of {@link question_engine_data_mapper}.
+ *
+ * @package   core_question
+ * @category  test
+ * @copyright 2014 The Open University
+ * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+
+defined('MOODLE_INTERNAL') || die();
+
+global $CFG;
+require_once(dirname(__FILE__) . '/../lib.php');
+require_once(dirname(__FILE__) . '/helpers.php');
+
+
+/**
+ * Unit tests for parts of {@link question_engine_data_mapper}.
+ *
+ * Note that many of the methods used when attempting questions, like
+ * load_questions_usage_by_activity, insert_question_*, delete_steps are
+ * tested elsewhere, e.g. by {@link question_usage_autosave_test}. We do not
+ * re-test them here.
+ *
+ * @copyright 2014 The Open University
+ * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class question_engine_data_mapper_testcase extends qbehaviour_walkthrough_test_base {
+
+    /**
+     * We create two usages, each with two questions, a short-answer marked
+     * out of 5, and and essay marked out of 10. We just start these attempts.
+     *
+     * Then we change the max mark for the short-answer question in one of the
+     * usages to 20, using a qubaid_list, and verify.
+     *
+     * Then we change the max mark for the essay question in the other
+     * usage to 2, using a qubaid_join, and verify.
+     */
+    public function test_set_max_mark_in_attempts() {
+
+        // Set up some things the tests will need.
+        $this->resetAfterTest();
+        $dm = new question_engine_data_mapper();
+
+        // Create the questions.
+        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');
+        $cat = $generator->create_question_category();
+        $sa = $generator->create_question('shortanswer', null,
+                array('category' => $cat->id));
+        $essay = $generator->create_question('essay', null,
+                array('category' => $cat->id));
+
+        // Create the first usage.
+        $q = question_bank::load_question($sa->id);
+        $this->start_attempt_at_question($q, 'interactive', 5);
+
+        $q = question_bank::load_question($essay->id);
+        $this->start_attempt_at_question($q, 'interactive', 10);
+
+        $this->finish();
+        $this->save_quba();
+        $usage1id = $this->quba->get_id();
+
+        // Create the second usage.
+        $this->quba = question_engine::make_questions_usage_by_activity('unit_test',
+                context_system::instance());
+
+        $q = question_bank::load_question($sa->id);
+        $this->start_attempt_at_question($q, 'interactive', 5);
+        $this->process_submission(array('answer' => 'fish'));
+
+        $q = question_bank::load_question($essay->id);
+        $this->start_attempt_at_question($q, 'interactive', 10);
+
+        $this->finish();
+        $this->save_quba();
+        $usage2id = $this->quba->get_id();
+
+        // Test set_max_mark_in_attempts with a qubaid_list.
+        $usagestoupdate = new qubaid_list(array($usage1id));
+        $dm->set_max_mark_in_attempts($usagestoupdate, 1, 20.0);
+        $quba1 = question_engine::load_questions_usage_by_activity($usage1id);
+        $quba2 = question_engine::load_questions_usage_by_activity($usage2id);
+        $this->assertEquals(20, $quba1->get_question_max_mark(1));
+        $this->assertEquals(10, $quba1->get_question_max_mark(2));
+        $this->assertEquals( 5, $quba2->get_question_max_mark(1));
+        $this->assertEquals(10, $quba2->get_question_max_mark(2));
+
+        // Test set_max_mark_in_attempts with a qubaid_join.
+        $usagestoupdate = new qubaid_join('{question_usages} qu', 'qu.id',
+                'qu.id = :usageid', array('usageid' => $usage2id));
+        $dm->set_max_mark_in_attempts($usagestoupdate, 2, 2.0);
+        $quba1 = question_engine::load_questions_usage_by_activity($usage1id);
+        $quba2 = question_engine::load_questions_usage_by_activity($usage2id);
+        $this->assertEquals(20, $quba1->get_question_max_mark(1));
+        $this->assertEquals(10, $quba1->get_question_max_mark(2));
+        $this->assertEquals( 5, $quba2->get_question_max_mark(1));
+        $this->assertEquals( 2, $quba2->get_question_max_mark(2));
+
+        // Test the nothing to do case.
+        $usagestoupdate = new qubaid_join('{question_usages} qu', 'qu.id',
+                'qu.id = :usageid', array('usageid' => -1));
+        $dm->set_max_mark_in_attempts($usagestoupdate, 2, 2.0);
+        $quba1 = question_engine::load_questions_usage_by_activity($usage1id);
+        $quba2 = question_engine::load_questions_usage_by_activity($usage2id);
+        $this->assertEquals(20, $quba1->get_question_max_mark(1));
+        $this->assertEquals(10, $quba1->get_question_max_mark(2));
+        $this->assertEquals( 5, $quba2->get_question_max_mark(1));
+        $this->assertEquals( 2, $quba2->get_question_max_mark(2));
+    }
+}