openerp中的左父母和右父母 [英] Parent left and Parent Right in openerp

问题描述

左父母和右父母是什么?

What is Parent left and Parent right?

它在 Openerp 中如何工作?

谢谢

推荐答案

正如Raphael Collet在中所解释的那样OpenERP服务器:

As Raphael Collet explains in his answer about OpenERP Server:

parent_left和parent_right是与以下内容相关的特殊字段 parent_id字段.这些字段的目的是进行查询 在层次结构中有效执行:使用parent_left和 parent_right，您可以检索节点的所有后代，而无需 进行递归查询.

parent_left and parent_right are special fields that are related to the parent_id field. The purpose of those fields is to make queries within the hierarchy execute efficiently: with parent_left and parent_right, you can retrieve all the descendants of a node without making recursive queries.

考虑层次结构中的两个节点A和B. A和B可以成为伙伴 例如，类别.它们的整数字段parent_left和 parent_right是这样的:

Consider two nodes A and B in the hierarchy. A and B can be partner categories, for instance. Their integer fields parent_left and parent_right are such that:

    B is a descendant of A in the hierarchy (defined by parent_id)

当且仅当

    A.parent_left < B.parent_left and
    A.parent_left < B.parent_right and 
    B.parent_left < A.parent_right and
    B.parent_right < A.parent_right

因此，假设您有六个合作伙​​伴类别，如下所示.你可以 通过遍历树来分配parent_left和parent_right.结果 在每个节点旁边的括号中显示.注意那里的值 是最优的实际上，您可以在数字上留出空白.

So, imagine that you have six partner categories like below. You can assign parent_left and parent_right by traversing the tree. The result is show in parentheses next to each node. Note that the values there are optimal; in practice, you can leave gaps in the numbers.

• 客户(1，10)
  • 消费者(2，3)
  • 合作伙伴(4，9)
    • 基本合作伙伴(5，6)
    • 金牌合作伙伴(7，8)
    • Customers (1, 10)
      • Consumers (2, 3)
      • Partners (4, 9)
        • Basic Partners (5, 6)
        • Gold Partners (7, 8)

        您可以使用单个SQL检索客户"的所有子类别 询问.请注意，值1和10是parent_left和 客户的parent_right；可以将它们作为查询的一部分进行检索 本身.

        You can retrieve all the subcategories of Customers with a single SQL query. Note that the values 1 and 10 are the parent_left and parent_right of Customers; they can be retrieved as part of the query itself.

            SELECT id FROM partner_category
            WHERE parent_left > 1 AND parent_left < 10
        

        最后一句话是可以更新parent_left和parent_right 而不遍历整个层次结构.删除节点不会 需要任何更改.要添加节点，您可以调整parent_left 和parent_right具有两个UPDATE查询:一个用于腾出一些空间" 在新节点祖先的parent_left和parent_right之间， 和一个移动新节点的parent_left和parent_right 跟随兄弟姐妹及其后代.所以parent_left和 parent_right可以得到有效维护.

        The last remark is that parent_left and parent_right can be updated without traversing the whole hierarchy. Removing a node does not require any change. For adding a node, you can adapt the parent_left and parent_right with two UPDATE queries: one to "make some space" between the parent_left and parent_right of the new node's ancestors, and one to shift the parent_left and parent_right of the new node's following siblings and their descendants. So parent_left and parent_right can be maintained efficiently.

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