Question

Hello I am trying to create a simple neo4j DB. I have a for loop that creates a new node for every file in a directory

for(file f : files){
        Node document = graphDb.createNode();
        document.setProperty( "name", f.toString().trim());
        graphDb.getReferenceNode().createRelationshipTo(document, MatrixRelationshipTypes.REFRENCE);

that works fine. Then I am trying to create a node for each name found in a file:

                Node pName = graphDb.createNode();
                pName.setProperty("name", name.toString());
                pName.createRelationshipTo(document, MatrixRelationshipTypes.CONTAINS_NAME);

The problem is it creates a Node for every name found, which I understand is what my code is telling it to do. What I really want is for it to create a node IF one of that name doesn not already exisist. And if one of the name does exist link it to both documents it exist in.

Any ideas??

Answer 1

You want to use an index. There are also auto-indexes which handle the indexing (at the end of the transaction for you).

Index<Node> nameIndex = graphDb.index().forNodes("names");

public Node getOrCreateNode(String name) {
  Node found = nameIndex.get("name",name).getSingle();
  if (found!=null) return found;
  Node nameNode = graphDb.createNode();
  nameNode.setProperty("name",name);
  nameIndex.add(nameNode, "name", name);
  return nameNode;
}

You can then also query the index for nodes using wildcards (Lucene search syntax).

IndexHits<Node> nodes = nameIndex.query("name:Jo*");