问题描述
我有一个非唯一节点(:Neighborhood)，该节点唯一地显示[:IN]一个(:City)节点.我想创建一个新的邻域节点并仅在该城市中不存在该邻域节点的情况下建立其关系.可以有多个具有相同名称的街区，但是每个街区必须在属性城市中唯一显示.
按照Gil的建议在这里进行操作:如果有关系，则返回节点不存在，我该怎么做:
MATCH a WHERE NOT (a:Neighborhood {name : line.Neighborhood})-[r:IN]->(c:City {name : line.City})
ON MATCH SET (a)-[r]-(c)
因此，只有在城市中尚不存在新邻居节点时，它才会创建.
**更新:**我已对其进行升级和配置，但仍然无法利用任何优化...
PROFILE LOAD CSV WITH HEADERS FROM "file://THEFILE" as line
WITH line LIMIT 0
MATCH (c:City { name : line.City})
MERGE (n:Neighborhood {name : toInt(line.Neighborhood)})-[:IN]->(c)
;
+--------------+------+--------+---------------------------+------------------------------+
| Operator | Rows | DbHits | Identifiers | Other |
+--------------+------+--------+---------------------------+------------------------------+
| EmptyResult | 0 | 0 | | |
| UpdateGraph | 5 | 16 | anon[340], b, neighborhood, line | MergePattern |
| SchemaIndex | 5 | 10 | b, line | line.City; :City(name) |
| ColumnFilter | 5 | 0 | line | keep columns line |
| Filter | 5 | 0 | anon[216], line | anon[216] |
| Extract | 5 | 0 | anon[216], line | anon[216] |
| Slice | 5 | 0 | line | { AUTOINT0} |
| LoadCSV | 5 | 0 | line | |
+--------------+------+--------+---------------------------+------------------------------+
我认为您可以为此简单地使用MERGE:
MATCH (c:City {name: line.City})
MERGE c<-[:IN]-(a:Neighborhood {name : line.Neighborhood})
如果尚未导入所有城市，则可以使用MERGE创建城市:
MATCH (c:City {name: line.City})
MERGE c<-[:IN]-(a:Neighborhood {name : line.Neighborhood})
但是要小心Eager运算符:
http://www.markhneedham .com/blog/2014/10/23/neo4j-cypher-avoiding-the-eager/
简而言之:您应该两次运行LOAD CSV(我想这就是您在这里所做的)，一次加载城市，一次加载社区.
I have a non-unique node (:Neighborhood) that uniquely appears [:IN] a (:City) node. I would like to create a new neighborhood node and establish its relationship ONLY if that neighborhood node does not exist in that city. There can be multiple neighborhoods that have the same name, but each neighborhood must appear uniquely appear in the property city.
Following the advice from the Gil's answer here: Return node if relationship is not present, how can I do something like:
MATCH a WHERE NOT (a:Neighborhood {name : line.Neighborhood})-[r:IN]->(c:City {name : line.City})
ON MATCH SET (a)-[r]-(c)
So then it would only create a new neighborhood node if it doesn't already exist in the city.
**UPDATE:**I upgraded and profiled it and still can't take advantage of any optimizations...
PROFILE LOAD CSV WITH HEADERS FROM "file://THEFILE" as line
WITH line LIMIT 0
MATCH (c:City { name : line.City})
MERGE (n:Neighborhood {name : toInt(line.Neighborhood)})-[:IN]->(c)
;
+--------------+------+--------+---------------------------+------------------------------+
| Operator | Rows | DbHits | Identifiers | Other |
+--------------+------+--------+---------------------------+------------------------------+
| EmptyResult | 0 | 0 | | |
| UpdateGraph | 5 | 16 | anon[340], b, neighborhood, line | MergePattern |
| SchemaIndex | 5 | 10 | b, line | line.City; :City(name) |
| ColumnFilter | 5 | 0 | line | keep columns line |
| Filter | 5 | 0 | anon[216], line | anon[216] |
| Extract | 5 | 0 | anon[216], line | anon[216] |
| Slice | 5 | 0 | line | { AUTOINT0} |
| LoadCSV | 5 | 0 | line | |
+--------------+------+--------+---------------------------+------------------------------+
I think you could simply use MERGE for this:
MATCH (c:City {name: line.City})
MERGE c<-[:IN]-(a:Neighborhood {name : line.Neighborhood})
If you haven't already imported all of the cities, you can create those with MERGE:
MATCH (c:City {name: line.City})
MERGE c<-[:IN]-(a:Neighborhood {name : line.Neighborhood})
But beware of the Eager operator:
http://www.markhneedham.com/blog/2014/10/23/neo4j-cypher-avoiding-the-eager/
In short: You should run your LOAD CSV (I assume that's what you're doing here) twice, once to load the cities and once to load the neighborhoods.
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