Method countRelations

/**
 * Adds Count relations for Category and Tag Managers
 *
 * @param   \stdClass[]  &$items  The category or tag objects
 * @param   \stdClass    $config  Configuration object allowing to use a custom relations table
 *
 * @return  \stdClass[]
 *
 * @since   3.9.1
 */
public static function countRelations(&$items, $config)
{
    $db = Factory::getDbo();
    // Allow custom state / condition values and custom column names to support custom components
    $counter_names = isset($config->counter_names) ? $config->counter_names : array('-2' => 'count_trashed', '0' => 'count_unpublished', '1' => 'count_published', '2' => 'count_archived');
    // Index category objects by their ID
    $records = array();
    foreach ($items as $item) {
        $records[(int) $item->id] = $item;
    }
    // The relation query does not return a value for cases without relations of a particular state / condition, set zero as default
    foreach ($items as $item) {
        foreach ($counter_names as $n) {
            $item->{$n} = 0;
        }
    }
    // Table alias for related data table below will be 'c', and state / condition column is inside related data table
    $related_tbl = '#__' . $config->related_tbl;
    $state_col = 'c.' . $config->state_col;
    // Supported cases
    switch ($config->relation_type) {
        case 'tag_assigments':
            $recid_col = 'ct.' . $config->group_col;
            $query = $db->getQuery(true)->from($db->quoteName('#__contentitem_tag_map', 'ct'))->join('INNER', $db->quoteName($related_tbl, 'c'), $db->quoteName('ct.content_item_id') . ' = ' . $db->quoteName('c.id') . ' AND ' . $db->quoteName('ct.type_alias') . ' = :extension')->bind(':extension', $config->extension);
            break;
        case 'category_or_group':
            $recid_col = 'c.' . $config->group_col;
            $query = $db->getQuery(true)->from($db->quoteName($related_tbl, 'c'));
            break;
        default:
            return $items;
    }
    /**
     * Get relation counts for all category objects with single query
     * NOTE: 'state IN', allows counting specific states / conditions only, also prevents warnings with custom states / conditions, do not remove
     */
    $query->select([$db->quoteName($recid_col, 'catid'), $db->quoteName($state_col, 'state'), 'COUNT(*) AS ' . $db->quoteName('count')])->whereIn($db->quoteName($recid_col), array_keys($records))->whereIn($db->quoteName($state_col), array_keys($counter_names))->group($db->quoteName([$recid_col, $state_col]));
    $relationsAll = $db->setQuery($query)->loadObjectList();
    // Loop through the DB data overwriting the above zeros with the found count
    foreach ($relationsAll as $relation) {
        // Sanity check in case someone removes the state IN above ... and some views may start throwing warnings
        if (isset($counter_names[$relation->state])) {
            $id = (int) $relation->catid;
            $cn = $counter_names[$relation->state];
            $records[$id]->{$cn} = $relation->count;
        }
    }
    return $items;
}