Hi all,
I've been doing preliminary evaluations on some Neo4j operations. One of which
rises from a specific need in my application:
My method will get a List of node ids (stored in the nodes' properties) and
need to retrieve exactly these nodes from the GraphDB. This should happen as
fast as possible, of course. I used an index for the ids. My code is as follows:
private static final int SAMPLE_SIZE = 100000;
...
GraphDatabaseService graphDb = new EmbeddedGraphDatabase("tmp/graphdb");
Transaction t = graphDb.beginTx();
IndexManager im = graphDb.index();
Index<Node> ni = im.forNodes("nodes");
( (LuceneIndex<Node>) ni ).setCacheCapacity( "nodes", 500000 );
for (int i = 0; i < SAMPLE_SIZE; ++i) {
Node n = graphDb.createNode();
n.setProperty("id", i);
ni.add(n, "id", n.getProperty("id"));
}
t.success();
t.finish();
long time = System.currentTimeMillis();
for (int i = 0; i < SAMPLE_SIZE; ++i) {
Node n = ni.get("id", i).getSingle();
}
System.out.println(System.currentTimeMillis() - time);
It works, but is rather slow. If I do the last loop a second time, the Lucene
cache kicks in and reduces the required time by half. But then it's still some
time (2000ms on my machine).
When I do the exact same thing with a HashMap for example, the same loop (with
call Node n = ni.get("id", i).getSingle();) takes about 10ms.
I now HashMaps have other drawbacks such like memory consumption. For my use
case this wouldn't be the problem, however, as I would only have to cache about
1M nodes which is perfectly possible in a HashMap. My main question is: Have I
done something wrong in my usage of the Lucene index? Can it be sped up
somehow? Or will I always be served better performance wise using a HashMap for
such cases where I have a large amount of single queries?
Thank you and best regards,
Erik
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