function SetOverride($attrname, $attrtype, $values)
{
assert(is_string($attrname));
assert(in_array($attrtype, array(SPH_ATTR_INTEGER, SPH_ATTR_TIMESTAMP, SPH_ATTR_BOOL, SPH_ATTR_FLOAT, SPH_ATTR_BIGINT)));
assert(is_array($values));
$this->_overrides[$attrname] = array("attr" => $attrname, "type" => $attrtype, "values" => $values);
}