问题描述
我对 neo4j 还很陌生,我想编写一个查询来读取 .json 格式并创建节点图。下面是我的查询,它在没有 null 属性的文件中成功,当我的 json 文件中有 null 属性时不成功。
代码:
CALL apoc.load.json("file:/graph-phase1-labelled.json") YIELD value
UNWIND value.nodes as nodes
UNWIND nodes.properties as prop
MERGE(n1:Node{src:prop.sourceIP})
MERGE(n2:Node{dst:prop.destIP})
WITH n1,n2,prop
MERGE (n1)-[:CONNECTED_TO]->(n2)
RETURN n1,prop
错误:
Cannot merge the following node because of null property value for 'src': (:Node {src: null})
有人知道什么可以解决问题吗?
解决方法
由于您无法合并 null 属性,因此您必须过滤掉其中包含 null 的行。示例:
CALL apoc.load.json("file:/graph-phase1-labelled.json") YIELD value
UNWIND value.nodes as nodes
UNWIND nodes.properties as prop
WHERE prop.sourceIP IS NOT NULL prop.destIP IS NOT NULL
WITH prop
MERGE(n1:Node{src:prop.sourceIP})
MERGE(n2:Node{dst:prop.destIP})
WITH n1,n2,prop
MERGE (n1)-[:CONNECTED_TO]->(n2)
RETURN n1,prop
,
我设法通过以下查询解决了这个问题:
call apoc.load.json("file:/graph-phase1-labelled1.json") yield value
unwind value.nodes as nodes
unwind nodes.properties as prop
with prop where prop.sourceIP is not null
with prop where prop.destIP is not null
merge(n1:Node{src:prop.sourceIP})
merge(n2:Node{dest:prop.destIP})
with prop,n1,n2
merge (n1)-[ :connected_to]->(n2)
return n1,prop