function nextvalSequence($sequence)
{
/* This double-cleaning is deliberate */
$f_schema = $this->_schema;
$this->fieldClean($f_schema);
$this->clean($f_schema);
$this->fieldClean($sequence);
$this->clean($sequence);
$sql = "SELECT pg_catalog.NEXTVAL('\"{$f_schema}\".\"{$sequence}\"')";
return $this->execute($sql);
}