Missing index for guest display name lookup

[ChristophWurst]

guests/lib/UserBackend.php

Lines 220 to 234 in ff10aed

	$query->select('uid', 'displayname')
	->from('guests_users', 'u')
	->leftJoin('u', 'preferences', 'p', $query->expr()->andX(
	$query->expr()->eq('userid', 'uid'),
	$query->expr()->eq('appid', $query->expr()->literal('settings')),
	$query->expr()->eq('configkey', $query->expr()->literal('email')))
	)
	// sqlite doesn't like re-using a single named parameter here
	->where($query->expr()->iLike('uid', $query->createPositionalParameter('%' . $this->dbConn->escapeLikeParameter($search) . '%')))
	->orWhere($query->expr()->iLike('displayname', $query->createPositionalParameter('%' . $this->dbConn->escapeLikeParameter($search) . '%')))
	->orWhere($query->expr()->iLike('configvalue', $query->createPositionalParameter('%' . $this->dbConn->escapeLikeParameter($search) . '%')))
	->orderBy($query->func()->lower('displayname'), 'ASC')
	->orderBy('uid_lower', 'ASC')
	->setMaxResults($limit)
	->setFirstResult($offset);

does builds the query

SELECT
  `uid`,
  `displayname`
FROM
  `oc_guests_users` `u`
  LEFT JOIN `oc_preferences` `p` ON (`userid` = `uid`)
  AND (`appid` = ?)
  AND (`configkey` = ?)
WHERE
  (`uid` COLLATE `utf8mb4_general_ci` LIKE ?)
  OR (
    `displayname` COLLATE `utf8mb4_general_ci` LIKE ?
  )
  OR (
    `configvalue` COLLATE `utf8mb4_general_ci` LIKE ?
  )
ORDER BY
  `uid_lower` ASC
LIMIT
  ?

that does not use any index.

Query hash is d9703f573d96020de3765fcd7a85e628