public function getDropForeignKeyDDL(ForeignKey $fk)
    {
        if ($fk->isSkipSql()) {
            return;
        }
        $pattern = "
ALTER TABLE %s DROP CONSTRAINT %s;
";

        return sprintf($pattern,
            $this->quoteIdentifier($fk->getTable()->getName()),
            $this->quoteIdentifier($fk->getName())
        );
    }