1.能详细说说每个参数的用法吗？ 2.比如我想要返回的单个path不产生回路，比如：D1到A1的路径不能出现D1-A1-B1-A1，即某个点只能路过一次，应该用哪个参数？NODE_LEVEL？NODE_PATH？

value description RELATIONSHIP_PATH

For each returned node there’s a (relationship wise) unique path from the start node to it. This is Cypher’s default expansion mode.

NODE_GLOBAL

A node cannot be traversed more than once. This is what the legacy traversal framework does.

NODE_LEVEL

Entities on the same level are guaranteed to be unique.

NODE_PATH

For each returned node there’s a unique path from the start node to it.

NODE_RECENT

This is like NODE_GLOBAL, but only guarantees uniqueness among the most recent visited nodes, with a configurable count. Traversing a huge graph is quite memory intensive in that it keeps track of all the nodes it has visited. For huge graphs a traverser can hog all the memory in the JVM, causing OutOfMemoryError. Together with this Uniqueness you can supply a count, which is the number of most recent visited nodes. This can cause a node to be visited more than once, but scales infinitely.

RELATIONSHIP_GLOBAL

A relationship cannot be traversed more than once, whereas nodes can.

RELATIONSHIP_LEVEL

Entities on the same level are guaranteed to be unique.

RELATIONSHIP_RECENT

Same as for NODE_RECENT, but for relationships.

NONE

No restriction (the user will have to manage it)