C:/xampp/htdocs/moodle/mod/quiz/db/upgradelib.php

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<?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/>.

defined('MOODLE_INTERNAL') || die();

require_once($CFG->dirroot . '/mod/quiz/locallib.php');


function quiz_upgrade_very_old_question_sessions($attempt) {
    global $DB;
    // The old quiz model only allowed a single response per quiz attempt so that there will be
    // only one state record per question for this attempt.

    // We set the timestamp of all states to the timemodified field of the attempt.
    $DB->execute("UPDATE {question_states} SET timestamp = ? WHERE attempt = ?",
            array($attempt->timemodified, $attempt->uniqueid));

    // For each state we create an entry in the question_sessions table, with both newest and
    // newgraded pointing to this state.
    // Actually we only do this for states whose question is actually listed in $attempt->layout.
    // We do not do it for states associated to wrapped questions like for example the questions
    // used by a random question
    $session = new stdClass();
    $session->attemptid = $attempt->uniqueid;
    $session->sumpenalty = 0;
    $session->manualcomment = '';
    $session->manualcommentformat = FORMAT_HTML;
    $session->flagged = 0;

    $questionlist = str_replace(',0', '', quiz_clean_layout($attempt->layout, true));
    if (!$questionlist) {
        return;
    }
    list($usql, $question_params) = $DB->get_in_or_equal(explode(',', $questionlist));
    $params = array_merge(array($attempt->uniqueid), $question_params);

    if ($states = $DB->get_records_select('question_states',
            "attempt = ? AND question $usql", $params)) {
        foreach ($states as $state) {
            if ($DB->record_exists('question_sessions',
                    array('attemptid' => $attempt->uniqueid, 'questionid' => $state->question))) {
                // It was possible for the code to get here when some of the necessary
                // question_sessions were already in the database. That lead to a
                // unique key violation, so we manually detect and avoid that.
                continue;
            }
            $session->newgraded = $state->id;
            $session->newest = $state->id;
            $session->questionid = $state->question;
            $DB->insert_record('question_sessions', $session, false);
        }
    }

    // It was possible to have old question_states records for this attempt but
    // pointing to questionids that were no longer in quiz_attempt->layout.
    // That makes no sense, and will break things later in the upgrade, so delete
    // those now.
    list($qidsql, $params) = $DB->get_in_or_equal(explode(',', $questionlist),
            SQL_PARAMS_QM, 'param', false);
    $params[] = $attempt->uniqueid;
    $DB->delete_records_select('question_states', "question $usql AND attempt = ?", $params);
}