Neo4j.rb:在将一个节点替换为另一个节点之前，先转移所有关系 [英] Neo4j.rb : transfer all relationships before replacing a node by another

问题描述

在删除第一个节点之前，我试图将所有传入和传出关系(包括它们的属性)从一个节点转移到另一个节点.他们都有相同的标签.

I'm trying to transfert all ingoing and outgoing relationships (including their properties) from a node to another, before deleting the first one. they both have the same label.

讨论从这里开始: Neo4j Cypher:在替换节点之前转移所有关系另一个

node_query = Neo4j::Session.query.match(old_node: {uuid: node1.uuid}).match(new_node: {uuid: node2.uuid})

types = node_query.match('node-[rel]-()').pluck('DISTINCT type(rel)')

types.each do |type|
  node_query.match('old_node-[rel]->(other)').with(:old_node, :rel, :other).create("new_node-[new_rel]->other").set('new_rel = rel').exec
  node_query.match('old_node<-[rel]-(other)').with(:old_node, :rel, :other).create("new_node<-[new_rel]-other").set('new_rel = rel').exec
end

当我尝试实现该错误时

new_rel not defined (line 1, column 160)
"MATCH
  (old_node {uuid: "YYYY"}),
  (new_node {uuid: "XXXX"}),
  oldnode-[rel]->(other)
WITH old_node, rel, other SET new_rel = rel
CREATE new_node-[new_rel]->other" ^

---

我尝试了另一种仅适用于Neo4j :: ActiveRel rels的方法，因为其他方法没有to_node属性.看来它还是不会复制关系属性:

---

I tried another way which works only for the Neo4j::ActiveRel rels, beacause for the others there's no to_node property. It seems that it doesn't copy the relationship properties anyway :

relations = old_node.rels(dir: :outgoing)
relations.each do |rel|
  if defined? rel.to_node
    new_node.create_rel(rel.type, rel.to_node, rel.props)
  end
end

relations = self.rels(dir: :incoming)
relations.each do |rel|
  if defined? rel.from_node
    rel.from_node.create_rel(rel.type, new_node, rel.props)
  end
end

推荐答案

嗯，现在我看到了错误，我想我知道原始答案有什么问题.我也会看看您的其他解决方案，但是这就是我将如何解决原始问题的方法(通过添加一个中断使SET出现在CREATE之后):

Ah, now that I see the error I think I know what was wrong with the original answer. I'll look at your other solution too, but here is how I would fix the original (by adding a break to make the SET come after the CREATE):

# Assuming node already loaded
node_query = Neo4j::Session.query.match(node: {neo_id: node.neo_id}, new_node: {neo_id: new_node.neo_id})

types = node_query.match('node-[rel]-()').pluck('DISTINCT type(rel)')

types.each do |type|
  node_query.match('node-[rel:#{type}]->(other)').
    where('other <> new_node').
    with(:node, :new_node, :rel, :other).
    create("new_node-[new_rel:#{type}]->other").
    break.set('new_rel = rel').exec

  node_query.match('node<-[rel:#{type}]-(other)').
    where('other <> new_node').
    with(:node, :new_node, :rel, :other).
    create("new_node<-[new_rel:#{type}]-other").
    break.set('new_rel = rel').exec
end

这篇关于Neo4j.rb:在将一个节点替换为另一个节点之前，先转移所有关系的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！