function unix_timestamp() does not exist (postgresql)

CentOS 7.4
Postgresql 10.2
Php 7.1.14

Drupal\Core\Database\DatabaseExceptionWrapper : SQLSTATE[42883]: Undefined function: 7 ERROR: function unix_timestamp() does not exist LINE 1: SELECT id FROM drupal_poll_field_data WHERE (UNIX_TIMESTAMP(... ^ HINT: No function matches the given name and argument types. You might need to add explicit type casts.: SELECT id FROM {poll_field_data} WHERE (UNIX_TIMESTAMP() > (created + runtime)) AND status = 1 AND runtime <> 0; Array ( ) dans Drupal\poll\PollStorage->getExpiredPolls() (ligne 86 de /var/www/html/site/modules/poll/src/PollStorage.php).

A similar issue has been found in roundcube, with a workaround: https://github.com/roundcube/roundcubemail/issues/396

HTH,
Keep up the good work !