public function getUniqueConstraintDeclarationSQL($name, Index $index)
    {
        $columns = $index->getColumns();
        $name    = new Identifier($name);

        if (count($columns) === 0) {
            throw new InvalidArgumentException("Incomplete definition. 'columns' required.");
        }

        return 'CONSTRAINT ' . $name->getQuotedName($this) . ' UNIQUE ('
            . $this->getIndexFieldDeclarationListSQL($index)
            . ')' . $this->getPartialIndexSQL($index);
    }