Alter field hostname to identifier in the {flood} table.
function system_update_7032() {
db_drop_index('flood', 'allow');
db_change_field('flood', 'hostname', 'identifier', array(
'type' => 'varchar',
'length' => 128,
'not null' => TRUE,
'default' => '',
));
db_add_index('flood', 'allow', array(
'event',
'identifier',
'timestamp',
));
}