Neo4j Client UNWIND with “DateTime?”

问题

I'm currently trying to unwind a list of TravelEdges that has a "DateTime?" but I keep receiving the following error:

{"CypherTypeException: Type mismatch: expected a map but was String(\"2018-05-21T08:38:00\")"}

I'm currently using the latest version of neo4j (3.4.8) and was wondering if someone could assist?

Also, is there a more efficient way of adding the edges without having two matches? The Id's are unique.

List<TravelEdge> travelpoints = new List<TravelEdge>();

//Add stuff to list

graphClient.Cypher
.Unwind(travelpoints, "sc")
.Match("(s1:Node { Id: sc.Id1})")
.Match("(s2:Node { Id: sc.Id2})")
.Merge("(s1)-[t:Travels_To]->(s2)")
.OnCreate()
.Set("t.Time = sc.TravelTime")
.ExecuteWithoutResults();


public class Node{

//Unique
public long Id {get;set;}

}

public class Edge {

public DateTime? TravelTime {get;set;}

}

public class TravelEdge{

public long Id1 {get;set;}

public long Id2 {get;set;}

public DateTime? TravelTime {get;set;}
}

回答1:

@cypbersam is correct regarding your second query, but your sc is a map, as your TravelEdge class is treated as a map by the DB.

I've taken the code pretty much verbatim (see below) and when I run it with the GraphClient or the BoltGraphClient it works totally fine for me. So, I guess this could be a problem with the version of Neo4jClient - what version are you using?

Working Code Below

Be careful if you copy / paste, I completely delete the DB in the first couple of lines

void Main()
{
    //var graphClient = new GraphClient(new Uri("http://localhost:7474/db/data"), "neo4j", "neo");
    var graphClient = new BoltGraphClient("bolt://localhost:7687", "neo4j", "neo");
    graphClient.Connect();

    graphClient.Cypher.Match("(n)").DetachDelete("n").ExecuteWithoutResults();

    List<TravelEdge> travelpoints = new List<TravelEdge>{
        new TravelEdge { Id1 = 1, Id2 = 2, TravelTime = new DateTime(2000,1,1) },
        new TravelEdge { Id1 = 2, Id2 = 3, TravelTime = new DateTime(2000,1,2) },
        new TravelEdge { Id1 = 3, Id2 = 4, TravelTime = new DateTime(2000,1,3) },
        new TravelEdge { Id1 = 4, Id2 = 5, TravelTime = null },
    };

    var ids = new [] {1,2,3,4,5};
    graphClient.Cypher
        .Unwind(ids, "id")
        .Merge("(a:Node {Id: id})")
        .ExecuteWithoutResults();



    //Add stuff to list
    graphClient.Cypher
        .Unwind(travelpoints, "sc")
        .Match("(s1:Node { Id: sc.Id1})")
        .Match("(s2:Node { Id: sc.Id2})")
        .Merge("(s1)-[t:Travels_To]->(s2)")
        .OnCreate()
        .Set("t.Time = sc.TravelTime")
        .ExecuteWithoutResults();
}


public class Node{
    public long Id {get;set;}
}

public class TravelEdge {
    public long Id1 {get;set;}
    public long Id2 {get;set;}
    public DateTime? TravelTime {get;set;}
}

回答2:

Each sc value is a String, but your query is trying to use it as if it is a map. That is, sc.Id1 and sc.Id2 do not make any sense when sc is a String instead of a map. You need to change the travelpoints value so that it is a list of maps with Id1 and Id2 values.
There is no way to ensure that the t:Travels_To relationship exists between 2 specific nodes without looking up those nodes. However, to help speed up the lookups, you can create an index or uniqueness constraint on :Node(Id).

来源：https://stackoverflow.com/questions/52680320/neo4j-client-unwind-with-datetime

标签

neo4j

neo4jclient