Neo4j-关于语法apoc触发器的问题

问题描述

我有以下包含APOC程序的APOC触发器。这可以按需工作，但是我想知道我是否使用了很多WITH语句，这是可行的方法吗？还是有更好的方法来重构此代码。我仍然是neo4j的新手，所以不确定。

I have the following APOC trigger which contains a apoc procedure. This works as desired but I am wondering if I used a lot of WITH statements, is that the way to go? or is there a better way to refactor this code. I am still new to neo4j so not sure.

控制流程-每当创建注册节点时，它都会创建一个SPerson节点，并根据其大小（SPerson节点的数量）来创建

The control flow- Whenever the Enrollment node is created, it creates an SPerson node and depending on the size(number of SPerson nodes) it creates an enrolled or waitlist(if size>3, and deletes enrolled relation) relation with the course node.

CALL apoc.trigger.add('loadEnrollments',
"UNWIND apoc.trigger.nodesByLabel($assignedLabels, 'Enrollment') AS node
 MERGE (p1:SPerson { name: node.name, cell: node.cell, created_at: node.created_at})
 WITH p1, node
 MATCH (c:Course {name: 'Paradigm Shifting 101'})
 WITH node
 MATCH (n:SPerson)
 WITH node, COUNT(n) as size
 CALL apoc.do.when(
 size>3,
 'MATCH(p1:SPerson),(c:Course)
 WHERE p1.name=node.name
 CREATE (p1)-[:Waitlist]->(c)
 WITH p1,c
 MATCH (e:Enrollment) DETACH DELETE e',
 'MATCH(p1:SPerson),(c:Course)
 WHERE p1.name=node.name
 CREATE (p1)-[:Enrolled]->(c)
 WITH p1,c
 MATCH (e:Enrollment) DETACH DELETE e', {node:node}) YIELD value
 DETACH DELETE node",

 { phase: 'after' });

推荐答案

您应该：

• 最小化查询必须处理的数据行数，并且


• 不要不必要地重复操作。

请牢记这些规则，该查询可能对您有效（有效）：

With those rules in mind, this query may work (efficiently) for you:

CALL apoc.trigger.add(
  'loadEnrollments',
  "
  CALL apoc.cypher.doIt('MATCH (e:Enrollment) DETACH DELETE e', {}) YIELD value
  WITH value
  MATCH (n:SPerson)
  WITH COUNT(n) as size
  MATCH (c:Course {name: 'Paradigm Shifting 101'})
  UNWIND apoc.trigger.nodesByLabel($assignedLabels, 'Enrollment') AS node
  MERGE (p1:SPerson {name: node.name, cell: node.cell, created_at: node.created_at})
  DETACH DELETE node
  CALL apoc.create.relationship(p1, CASE WHEN size > 3 THEN 'Waitlist' ELSE 'Enrolled' END, {}, c) YIELD rel
  ",
  { phase: 'after' }
);

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