Serialization failure: 1213 Deadlock found when trying to get lock; try restarting transaction #7005

Steps to reproduce

1. removing multiple files

Expected behaviour

Fast remove

Actual behaviour

The remove for every second file takes time and the log shows the following error.

tail -f /var/log/nginx/error.log
#6 [internal fu" while reading response header from upstream, client: 109.69.230.220, server: start.boxu.nl, request: "PUT /remote.php/dav/fil es/btslogisticsfotos/Fotos/JS%20GREENSTAR/25-10%20(4).JPG HTTP/1.1", upstream: "fastcgi://unix:/run/php/php7.0-fpm.boxu.sock:", host: "start.b oxu.nl"
2017/10/30 08:48:41 [error] 8921#8921: *610137 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught PDOException: SQLSTATE[40001]: Serialization failure: 1213 Deadlock found when trying to get lock; try restarting transaction in /var/www/html/3rdparty/doctrine/dbal/lib/Do ctrine/DBAL/Driver/PDOStatement.php:91
Stack trace:
#0 /var/www/html/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Driver/PDOStatement.php(91): PDOStatement->execute(NULL)
#1 /var/www/html/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(1006): Doctrine\DBAL\Driver\PDOStatement->execute()
#2 /var/www/html/lib/private/DB/Connection.php(213): Doctrine\DBAL\Connection->executeUpdate('UPDATE oc_file...', Array, Array) #3 /var/www/html/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Query/QueryBuilder.php(208): OC\DB\Connection->executeUpdate('UPDATE oc_file...', A rray, Array)
#4 /var/www/html/lib/private/DB/QueryBuilder/QueryBuilder.php(213): Doctrine\DBAL\Query\QueryBuilder->execute()
#5 /var/www/html/lib/private/Lock/DBLockingProvider.php(278): OC\DB\QueryBuilder\QueryBuilder->execute()
#6 [internal fu" while reading response header from upstream, client: 46.44.173.251, server: start.boxu.nl, request: "GET /avatar/aknobbe/32?v =2 HTTP/2.0", upstream: "fastcgi://unix:/run/php/php7.0-fpm.boxu.sock:", host: "start.boxu.nl"

Server configuration

Operating system:
Ubuntu 16.10

Web server:
NGING 1.10

Database:
MySQL

PHP version:
PHP 7

Nextcloud version: (see Nextcloud admin page)
12.0.3