neo4j - 如何在 Neo4j 中使用带有 `with` 的 `call.apoc.do.when` 语句？

Question

首先，您可以使用以下命令创建示例节点，

CREATE (t1:Title { tid: '123abc'})
CREATE (t2:Title { tid: '123def'})
CREATE (t3:Title { tid: '123456'})
CREATE (t4:Title { tid: '123789'})
CREATE (u:User { pid: '456def'})

CREATE (t1)-[r:TO]->(t2)
CREATE (t2)-[r:TO]->(t3)
CREATE (t3)-[r:TO]->(t4)
CREATE (u)-[r:LIKE]->(t3)

这是图表，

我在 Neo4j 中有一个类似的查询，

MATCH (t1:Title)-[r:TO]->(t2:Title)
WHERE t1.tid = '123abc'
AND NOT exists((t2)<-[:LIKE|:DISLIKE|:LOVE]-(:User {pid: '456def'}))
WITH COLLECT(r) AS rels
LIMIT 1

WITH rels
CALL apoc.do.when(
    SIZE(rels) > 0,
    'RETURN REDUCE(total = 0, x IN rels | total + x.weight) AS result',
    'RETURN 0 AS result'
) YIELD value
RETURN value.result

我想在 rels 博客中使用 do.when 变量。 SIZE(rels) > 0 表达式没有问题，但是在 if statement 中返回这样的错误，

Failed to invoke procedure apoc.do.when: Caused by: org.neo4j.exceptions.SyntaxException: Variable rels not defined (line 1, column 31 (offset: 30))"RETURN REDUCE(total = 0, x IN rels | total + x.weight) AS result"

我是 Neo4j 的新手。我认为， REDUCE 有一个特殊情况。我怎么解决这个问题？提前致谢。

Answer 1

查看 documentation ，您可以添加包含内部语句参数的第三个参数:

MATCH (t1:Title)-[r:TO]->(t2:Title)
WHERE t1.tid = '123abc'
AND NOT exists((t2)<-[:LIKE|:DISLIKE|:LOVE]-(:User {pid: '456def'}))
WITH COLLECT(r) AS rels
LIMIT 1

WITH rels
CALL apoc.do.when(
    SIZE(rels) > 0,
    'RETURN REDUCE(total = 0, x IN rels | total + x.weight) AS result',
    'RETURN 0 AS result',
    {rels:rels}
) YIELD value
RETURN value.result