扩展Neo4j

jieforest

Then run:

1. rake neo4j:create

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… to create your graph. I’ll explain why we created this particular graph in a follow up blog post, but for now back to our MyService.java file. We will be using the GlobalGraphOperationstool and adding the following:

1. 
   
2. 01.import org.neo4j.tooling.GlobalGraphOperations;
   
3. 02.import org.neo4j.graphdb.Node;
   
4. 03.import org.neo4j.graphdb.Relationship;
   
5. 04.
   
6. 05.@GET
   
7. 06.@Path("/warmup")
   
8. 07.public String warmUp(@Context GraphDatabaseService db) {
   
9. 08.Node start;
   
10. 09.for ( Node n : GlobalGraphOperations.at( db ).getAllNodes() ) {
    
11. 10.n.getPropertyKeys();
    
12. 11.for ( Relationship relationship : n.getRelationships() ) {
    
13. 12.start = relationship.getStartNode();
    
14. 13.}
    
15. 14.}
    
16. 15.for ( Relationship r : GlobalGraphOperations.at( db ).getAllRelationships() ) {
    
17. 16.r.getPropertyKeys();
    
18. 17.start = r.getStartNode();
    
19. 18.}
    
20. 19.return "Warmed up and ready to go!";
    
21. 20.}

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jieforest

The code above first iterates through every node, brings up its properties, then calls up the relationships that node has. The code then iterates through every relationship, brings up its properties, then calls up the nodes it connects.

The sequence above effectively warms up your caches. If your graph fits in memory, this will prime the database. If your graph doesn’t fit in memory maybe you want to specify a certain set of nodes or relationships to warm up.

Either way you probably don’t want to run this over and over again or expose it to your end users. Remember what I said about being responsible with what you do here.

You’ll have to stop Neo4j, recompile it, copy the new jar file over the existing one, restart Neo4j, and run the command.

1. 1.rake neo4j:stop
   
2. 2.mvn clean package
   
3. 3.cp target/unmanaged-extension-template-1.0.jar neo4j/plugins/
   
4. 4.rake neo4j:start
   
5. 5.curl <a href="http://localhost:7474/example/service/warmup">http://localhost:7474/example/service/warmup</a>

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jieforest

If everything went well you should see:

1. Warmed up and ready to go!

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…and looking at your node and relationship caches in the Neo4j web admin server info page:

jieforest

If you don’t see these you are probably running the community edition instead of the enterprise edition. If the numbers are all zero then something went wrong. Retrace your steps and let me know if any part of this is confusing so I can do a better job explaining it. You can see my copy of MyService.java on github.

By the way, if you just want a warm cache you can do the same with Cypher by using:

1. 1.START n=node(*)
   
2. 2.MATCH n -[r?]-> ()
   
3. 3.RETURN count(n.property_i_do_not_have?)+count(r.property_i_do_not_have?)
   

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Did you know that “Cypher” is a term used to describe freestyle rap in a group setting?

jieforest

If you don’t see these you are probably running the community edition instead of the enterprise edition. If the numbers are all zero then something went wrong. Retrace your steps and let me know if any part of this is confusing so I can do a better job explaining it. You can see my copy of MyService.java on github.

By the way, if you just want a warm cache you can do the same with Cypher by using:

1. 1.START n=node(*)
   
2. 2.MATCH n -[r ]-> ()
   
3. 3.RETURN count(n.property_i_do_not_have )+count(r.property_i_do_not_have )

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Did you know that “Cypher” is a term used to describe freestyle rap in a group setting

jieforest

over.