Delete duplicate enrol plugins caused by Moodle bug MDL-29414

Moodle_EnrolDupeRemover.php

<?php

/**
 * Report and delete duplicate enrol plugins from courses, which arise by
 * Moodle bug http://tracker.moodle.org/browse/MDL-29414
 */
class Moodle_EnrolDupeRemover {

    /**
     * @var Zend_Db_Adapter_Abstract
     */
    protected $db;

    /**
     * @var string
     */
    protected $prefix;

    /**
     * @param Zend_Db_Adapter_Abstract $db
     * @param string $prefix
     */
    public function __construct(Zend_Db_Adapter_Abstract $db, $prefix = 'mdl_') {
        $this->db = $db;
        $this->prefix = $prefix;
    }

    /**
     * Get each combination of course and (guest/self) enrol plugin type where there
     * are more than 2 instances. The first plugin id is returned so it can used when
     * calling removeDupes()
     *
     * @return array
     */
    public function getDupesReport() {
        return $this->getAllDupes();
    }

    /**
     * Removes duplicate "guest" and "self" enrol plugins from all courses, and
     * returns number of duplicate rows removed for each course/type
     *
     * @return array
     */
    public function batchRemoveDupes() {
        $removals = array();
        foreach ($this->getAllDupes() as $row) {
            $removals[$row['courseId']][$row['enrolPluginType']] =
                $this->removeDupes(
                    $row['courseId'],
                    $row['enrolPluginType'],
                    $row['firstEnrolPluginId']);
        }
        return $removals;
    }

    /**
     * Remove duplicates of a sign type in a single course. If $originalPluginId is
     * not provided, 1 additional query is used.
     *
     * @param int $courseId
     * @param string $type (e.g. "guest")
     * @param int $originalPluginId (if not provided, function will find it)
     * @return int num rows removed
     */
    public function removeDupes($courseId, $type, $originalPluginId = null) {
        if (! $originalPluginId) {
            // assume the earliest id is the original
            $firstTwoIds = $this->db->fetchCol("
                SELECT id FROM {$this->prefix}enrol
                WHERE courseid = ?
                  AND enrol = ?
                ORDER BY id
                LIMIT 2
            ", array($courseId, $type));
            if (! $firstTwoIds || count($firstTwoIds) == 1) {
                return 0;
            } else {
                $originalPluginId = $firstTwoIds[0];
            }
        }
        // delete rest
        return $this->db->query("
            DELETE FROM {$this->prefix}enrol
            WHERE courseid = ?
              AND enrol = ?
              AND id != ?
        ", array($courseId, $type, $originalPluginId))->rowCount();
    }

    /**
     * @return array
     */
    protected function getAllDupes() {
        $typesSet = $this->db->quote($this->getSingularTypes());
        return $this->db->fetchAll("
            SELECT
                  courseid AS courseId,
                  MIN(id) AS firstEnrolPluginId,
                  enrol AS enrolPluginType,
                  (COUNT(*) - 1) AS numDuplicates
            FROM {$this->prefix}enrol
            WHERE enrol IN ($typesSet)
            GROUP BY courseid, enrol
            HAVING COUNT(*) > 1
            ORDER BY id
        ");
    }

    /**
     * @return array
     */
    protected function getSingularTypes() {
        return array('guest', 'self');
    }
}