neo4j

问题 I am trying to record the Neo4J algorithm execution. I run an algorithm 10 times, however the first run is always significantly longer than the rest of executions. For example: elapsed time = | 86345.0 | 3417.0 | 3416.0 | 4228.0 | 3369.0 | 3323.0 | 3338.0 | 3370.0 | 3775.0 | 3370.0 //ms Why is this happening? Is Neo4J smart enough to store already visited (read from DB) vertices in memory, thus from the second execution it reads from memory not the database? My datasets are small enough to

问题 Started with a new graph.db folder. Am using embedded graph db, java and cypher query to create nodes. It seems to create the nodes successfully. Have debugged and checked the result object. I want to now start the neo4j server to check the nodes in the browser. However, it gives the message: bash-4.2$ ./neo4j-community-2.2.1/bin/neo4j start WARNING : Max 1024 open files allowed, minimum of 40 000 recommended. See the Neo4j manual. Starting Neo4j Server... WARNING : not changing user process

问题 How can I get difference between 2 fields: r.rating_val and rw.rating_val and sum of these fields using neo4j query?I really appreciate any help. MATCH (a:user{id:"1"})-[r:`rating`]->(b), (w:user{id:"3"})-[rw:`rating`]->(b) RETURN DISTINCT b,r.rating_val ,rw.rating_val 回答1: Just subtract/add them in the return clause MATCH (a:user{id:"1"})-[r:`rating`]->(b), (w:user{id:"3"})-[rw:`rating`]->(b) RETURN DISTINCT b, r.rating_val-rw.rating_val as difference, r.rating_val+rw.rating_val as sum 回答2:

问题 I want to load a RDF file in Neo4j and turn this into a triplestore but I don't know if I can do this with the spqrl-plugin for Neo4j. I have been looking documentation for this plugin in https://github.com/neo4j-contrib/sparql-plugin, but I get 404 error when I try to open the documentation. The thing is, Do I need to develop a program which parse a RDF file and store the tuples in Neo4j with the turtle format I desire, or there is some feature in the sparql-endpoint which allow me to

问题 I have a linked list that is modelled in a circular fashion like so: (u:User) -[:LINK]->(a:NODELINK {linkId: 'aa'}) -[:LINK]->(b:NODELINK {linkId: 'bb'}) -[:LINK]->(c:NODELINK {linkId: 'cc'}) -[:LINK]->(d:NODELINK {linkId: 'dd'}) -[:LINK]->(u) When I query it starting at node (b:NODELINK {linkId: 'bb'}) I would like to match all nodes until I get to the end/start of the list. (The User node) When I run the following query: MATCH (u:USER) WITH u MATCH (nl:NODELINK)-[:LINK*]->(m) WHERE nl

问题 A related question is here: How to query property value when property name is a parameter? Let's say if I want to ask "Recommend me 500-dollar phones". And in my graph, I have: create (p:Product {name:"iPhone 1", price:"500", color:"white"}) create (p:Product {name:"iPhone 2", price:"400", color:"white"}) create (p:Product {name:"iPhone 3", price:"800", color:"black"}) Based on the language "Recommend me 500-dollar phones", I know I should query on the Product node, but I don't know the

问题 I have my java application deployed in websphere application server. I am successfully able to connect to neo4j from my java application using jdbc driver. But there are some performance issues with the approach i have followed. Currently neo4j server is running on Xms - 8G and Xmx-16GB. I have less amount of data that is aprox 40mb with 3100 nodes. When we test the performance over http with cypher, the performance is outstanding. But in the java application we are using the jdbc driver to

问题 I have the following paramObj and dbQuery paramObj = { email: newUser.email, mobilenumber: newUser.telephone, password: newUser.password, category: newUser.category, name: newUser.name, confirmuid: verificationHash, confirmexpire: expiryDate.valueOf(), rewardPoints: 0, emailconfirmed: 'false', paramVehicles: makeVehicleArray, paramVehicleProps: vehiclePropsArray } dbQuery = `CREATE (user:Person:Owner {email:$email}) SET user += apoc.map.clean(paramObj, ['email','paramVehicles',

问题 I have a following Cypher query: PROFILE MATCH (childD:Decision) WITH childD ORDER BY childD.createDate DESC SKIP 0 LIMIT 10 MATCH (childD:Decision)-[ru:CREATED_BY]->(u:User) OPTIONAL MATCH (childD:Decision)-[rup:UPDATED_BY]->(up:User) RETURN ru, u, rup, up, childD AS decision, [ (childD)-[rdt:BELONGS_TO]->(t:Tag) | t ] AS tags Right now on my Neo4j database (~23k Decision nodes) this query works ~50 ms and I don't understand or it uses index on childD.createDate field. This is PROFILE output

问题 My code is below, As per the documentation it should have given me the node values but it is throwing me exception Exception in thread "main" java.lang.ClassCastException: scala.collection.convert.Wrappers$SeqWrapper cannot be cast to org.neo4j.graphdb.Node at com.neo4j.performance.FetchData.main(FetchData.java:32) I'm using Neo4j 2.2.2. import org.neo4j.graphdb.Node; import org.neo4j.graphdb.Result; import org.neo4j.graphdb.Transaction; import java.util.Iterator; import org.neo4j.helpers