cypher

问题 I'm using LDBC dataset to test execution time in Neo4j 4.0.1, SF = 1, and I use java to connect Neo4j, ResultSummary.resultAvailableAfter() to get the execution time, which is the time to get the result and start streaming. But for the same query, when I run for the first time, the execution time seems reasonable, like hundreds of ms, but when I continue running this same query, the execution time becomes almost 0. I guess it's effect of query cache, but is there any proper approach to test

问题 I'm using LDBC dataset to test execution time in Neo4j 4.0.1, SF = 1, and I use java to connect Neo4j, ResultSummary.resultAvailableAfter() to get the execution time, which is the time to get the result and start streaming. But for the same query, when I run for the first time, the execution time seems reasonable, like hundreds of ms, but when I continue running this same query, the execution time becomes almost 0. I guess it's effect of query cache, but is there any proper approach to test

问题 SQL has "Having" clause, for example: SELECT LastName, COUNT(*) FROM Employees GROUP BY LastName HAVING COUNT(*) > 10; In Cypher, we can do count() START n=node(2) MATCH (n)-[r]->() RETURN type(r), count(*) But does Cypher have similar function as "Having", or is there any workaround? 回答1: Sure, having is just one of the many uses of query chaining with WITH which is similar to RETURN but determines which elements will be available in the next query part. WITH also supports ordering and

问题 I want to pick a node and get all of the nodes that are connected to it by relationship. Even this they are nth degree connections. What is the py2neo or simply cypher query for this? 回答1: This Cypher query should work (if the picked node has a myId value of 123 ): MATCH p=(n { myId:123 })-[*]-() UNWIND FILTER(x IN NODES(p) WHERE x <> n) AS node RETURN DISTINCT node; The FILTER function filters out the picked node, even if there are paths that cycle back to it. 来源： https://stackoverflow.com

问题 I want to pick a node and get all of the nodes that are connected to it by relationship. Even this they are nth degree connections. What is the py2neo or simply cypher query for this? 回答1: This Cypher query should work (if the picked node has a myId value of 123 ): MATCH p=(n { myId:123 })-[*]-() UNWIND FILTER(x IN NODES(p) WHERE x <> n) AS node RETURN DISTINCT node; The FILTER function filters out the picked node, even if there are paths that cycle back to it. 来源： https://stackoverflow.com

问题 The procedure apoc.create.relationship(n1,RelType,{},n2) behaves accordingly to the CREATE statement. If a relationship of type RelType already exists between nodes n1 and n2 apoc.create.relationship() will create a duplicate. Is there an equivalent version of apoc.create.relationship() that behaves like MERGE? 回答1: There is a procedure apoc.merge.relationship() which takes same parameters as apoc.create.relationship() and should do what you need. It has been mentioned in this blog post, but

问题 I'm running a query using Cypher in Neo4J where I have to compare a createdAt property of a node against a given time unit in Epoch milliseconds. This createdAt property is a string in the DateTime format, which is defined as - DateTime date with a precision of miliseconds, encoded as a string with the following format: yyyy-mm-ddTHH:MM:ss.sss+0000, where yyyy is a four-digit integer representing the year, the year, mm is a two-digit integer representing the month and dd is a two-digit

问题 I'm running a query using Cypher in Neo4J where I have to compare a createdAt property of a node against a given time unit in Epoch milliseconds. This createdAt property is a string in the DateTime format, which is defined as - DateTime date with a precision of miliseconds, encoded as a string with the following format: yyyy-mm-ddTHH:MM:ss.sss+0000, where yyyy is a four-digit integer representing the year, the year, mm is a two-digit integer representing the month and dd is a two-digit

问题 I am aware of the absence of a constraint for naming relationships, though it is tough to get one guideline and work with it over all the relationships that we might encounter. Would you go with something like this: (u:User)-[:LIKES]->(p:Post) (u:User)-[:LIKES]->(c:Comment) and then query based on the label; Or something like this: (u:User)-[:LIKES_POST]->(p:Post) (u:User)-[:LIKES_COMMENT]->(c:Comment) Another case is a threaded chat application where a User can start a thread with multiple

问题 One type of edges in my graph has a property called roles . It is an array/list of strings. It is like ["Bill Smoke", "Haskell Moore", "Tadeusz Kesselring", "Nurse Noakes", "Boardman Mephi", "Old Georgie"] How can I convert this to a string? I want to join them. With JS, I can do ['asd', '1', '2'].join('') . I want a similar functionality inside cypher 回答1: WITH REDUCE(mergedString = "",word IN ["Bill Smoke", "Haskell Moore", "Tadeusz Kesselring", "Nurse Noakes", "Boardman Mephi", "Old