原文： Operators are linked to their child nodes with dashed lines. When an operator has multiple children, they are arranged vertically, representing a right-to-left order. In the example above, operator 6 (VHASH JOIN) has operator 5 (EXCHANGE) as its left child and operator 4 (EXCHANGE) as its right child. 官方文档翻译： 算子与其孩子节点之间，以虚线连接。当一个算子存在多个孩子时，孩子算子从上之下排布，表示从右至左的关系。以上面的示例为例。6 号算子 VHASH JOIN 的左孩子是 5 号 EXCHANGE 算子，右孩子是 4 号 EXCHANGE 算子。