在 Neo4j Cypher 查询中仅返回简单路径 [英] Returning only simple paths in Neo4j Cypher query

问题描述

给定如下查询:

START n = node(123)
MATCH p = n-[r:LIKES*..3]->x
RETURN p;

我通过上述查询获得的结果路径包含循环.

The result paths that I get with the query above contain cycles.

如何只返回简单的路径?

How can I return only simple paths?

鉴于此示例:

• 如何避免具有重复节点的路径，例如:[Neo、Morpheus、Trinity、Morpheus、Neo]

推荐答案

指定路径的唯一性是 cypher 的一个计划功能.

Specifying the uniqueness of paths is a planned feature of cypher.

所以现在我们必须确定路径中没有节点是重复的.

So right now we have to ascertain that no node is a duplicate in the path.

有一个 ALL 谓词必须对集合(路径是)的所有元素都成立.使用 filter，您可以提取集合的元素，以确保某个条件成立.

There is an ALL predicate that must hold true for all elements of a collection (which a path is). And with filter you can extract the elements of an collection for that a certain condition holds true.

START neo=node(1) 
MATCH path= neo-[r:KNOWS*..4]->other 
WHERE ALL(n in nodes(path) where 
          1=length(filter(m in nodes(path) : m=n))) 
RETURN neo, LENGTH(path) AS length, EXTRACT(p in NODES(path) : p.name), other 
ORDER BY length

所以我所做的是:

• 对于路径n
的所有节点
• 过滤等于n
的节点的路径
• 确定该集合的长度
• 使用 ALL 断言每个 n
必须是 1

• For all nodes of the path n
• Filter the path for the nodes that are equal to n
• determine the length of that collection
• assert with ALL that it has to be ONE for each n

参见:http://console.neo4j.org/r/dpalbl

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