如何枚举通过Cypher返回的路径上的节点和关系(How to enumerate nodes and relationships along path returned via Cypher)

如何枚举通过Cypher返回的路径上的节点和关系(How to enumerate nodes and relationships along path returned via Cypher)

我在这里打开了这个问题： 如何使用where子句查找Neo4j中的特定子图以查找某个条件的路径。 然而，当我尝试做一些事情，比如得到关系类型我不能。

例如，我尝试了MATCH p = (n:Root)-[rs1*]->() WHERE ALL(rel in rs1 WHERE rel.relevance is null) RETURN nodes(p), TYPE(relationships(p))

但我得到错误：

Type mismatch: expected Relationship but was Collection<Relationship>

我想我需要使用WITH子句但不确定。

同样，我想要一个节点的ID，但也失败了。

I opened this question here: How to find specific subgraph in Neo4j using where clause to find a path of a certain criteria. Yet when I try to do things like get the relationship type I cannot.

For example I tried MATCH p = (n:Root)-[rs1*]->() WHERE ALL(rel in rs1 WHERE rel.relevance is null) RETURN nodes(p), TYPE(relationships(p))

But I get the error:

Type mismatch: expected Relationship but was Collection<Relationship>

I think I need to use a WITH clause but not sure.

Similarly I wanted the ID of a node but that also failed.

最满意答案

问题是relationships返回一个集合，而type函数仅适用于单个关系。 有两种主要方法可以解决这个问题。

使用UNWIND为每个关系获取一个单独的行：

MATCH p = (n:Root)-[rs1*]->() WHERE ALL(rel in rs1 WHERE rel.relevance is null) WITH relationships(p) AS rs UNWIND n, rs AS r RETURN n, type(r)

使用extract将结果放入列表中（每个根节点在一行中）：

MATCH p = (n:Root)-[rs1*]->() WHERE ALL(rel in rs1 WHERE rel.relevance is null) WITH n, relationships(p) AS rs RETURN n, extract(r IN rs | type(r))

甚至更短：

MATCH p = (n:Root)-[rs1*]->() WHERE ALL(rel in rs1 WHERE rel.relevance is null) RETURN n, extract(r IN relationships(p) | type(r))

The problem is that relationships returns a collection and the type function only works on a single relationship. There are two main approaches to solve this.

Use UNWIND to get a separate row for each relationship:

MATCH p = (n:Root)-[rs1*]->() WHERE ALL(rel in rs1 WHERE rel.relevance is null) WITH relationships(p) AS rs UNWIND n, rs AS r RETURN n, type(r)

Use extract to get the results in a list (in a single row per root node):

MATCH p = (n:Root)-[rs1*]->() WHERE ALL(rel in rs1 WHERE rel.relevance is null) WITH n, relationships(p) AS rs RETURN n, extract(r IN rs | type(r))

Or even shorter:

MATCH p = (n:Root)-[rs1*]->() WHERE ALL(rel in rs1 WHERE rel.relevance is null) RETURN n, extract(r IN relationships(p) | type(r))