Trying to count the relationships "the normal way" I find that oddly, I cannot see more than 100+x relationships, where x is the maximum number of relations ever added within a transaction. For example, if I add 91 relationships in a transation, and I count them, I have 91. I run the program again and I have 182, then I run the program again and I count 191, and any subsequent program runs will have the same 191 count. Is this a bug or am I missing something very important ?! Here's the sample code to try (run it 3 times and observe the ante-ante-last line on console: "Node `one` has 191 out rels, time=24,098,904"): (I don't know how I would place this code into a code block though)
/** * Licensed to Neo Technology under one or more contributor * license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright * ownership. Neo Technology licenses this file to you under * the Apache License, Version 2.0 (the "License"); you may * not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied. See the License for the * specific language governing permissions and limitations * under the License. */ package org.neo4j.examples; import java.io.*; import java.text.*; import org.neo4j.graphdb.*; import org.neo4j.graphdb.index.*; import org.neo4j.kernel.*; public class CalculateShortestPath { private static final int SHOWINFO_IF_COUNTING_REL_TOOK_MORE_THAN_ns = 2 * 300; private static final int SHOWINFO_IF_REL_TOOK_MORE_THAN_ns = 30000; private static final int SHOWEVERY_xTH_REL = 10000; private static final int HOWMANY_RELATIONSHIPS = 91; private static final String DB_PATH = "neo4j-shortest-path"; private static final String NAME_KEY = "name"; private static RelationshipType KNOWS = DynamicRelationshipType .withName( "KNOWS" ); private static GraphDatabaseService graphDb; private static Index<Node> indexService; private static DecimalFormat commaDelimitedFormatter = new DecimalFormat( "###,###" ); public static String number( double val ) { return commaDelimitedFormatter.format( val ); } public static String getTimeDelta( long start, long end ) { return commaDelimitedFormatter.format( end - start ); } public static void main( final String[] args ) { // deleteFileOrDirectory( new File( DB_PATH ) );// XXX: graphDb = new EmbeddedGraphDatabase( DB_PATH ); indexService = graphDb.index().forNodes( "nodes" ); registerShutdownHook(); Transaction tx = graphDb.beginTx(); try { Node one = getOrCreateNode( "one" ); DynamicRelationshipType moo = DynamicRelationshipType.withName( "moo" ); for ( int i = 1; i <= HOWMANY_RELATIONSHIPS; i++ ) { long start = System.nanoTime(); Relationship rel = one.createRelationshipTo( graphDb.createNode(), moo ); rel.setProperty( "relname", i ); long end = System.nanoTime(); if ( ( i % SHOWEVERY_xTH_REL == 0 ) || ( end - start > SHOWINFO_IF_REL_TOOK_MORE_THAN_ns ) ) { System.out.println( number( i ) + " timeDelta=" + number( end - start ) ); } } System.out.println( "counting..." ); long start = System.nanoTime(); Iterable<Relationship> rel = one.getRelationships( Direction.OUTGOING, moo ); long count = 0; long tstart = 0; for ( Relationship relationship : rel ) { long tend = System.nanoTime(); count++; if ( ( tend - tstart > SHOWINFO_IF_COUNTING_REL_TOOK_MORE_THAN_ns ) ) { System.out.println( number( count ) + " timeDelta=" + number( tend - tstart ) ); } tstart = System.nanoTime(); } long end = System.nanoTime(); System.out.println( "Node `" + one.getProperty( NAME_KEY ) + "` has " + number( count ) + " out rels, time=" + number( end - start ) ); // /* // * (Neo) --> (Trinity) // * \ ^ // * v / // * (Morpheus) --> (Cypher) // * \ | // * v v // * (Agent Smith) // */ // createChain( "Neo", "Trinity" ); // createChain( "Neo", "Morpheus", "Trinity" ); // createChain( "Morpheus", "Cypher", "Agent Smith" ); // createChain( "Morpheus", "Agent Smith" ); tx.success(); } finally { long start = System.nanoTime(); tx.finish(); long end = System.nanoTime(); System.out.println( "tx.finish() time=" + number( end - start ) ); } // So let's find the shortest path between Neo and Agent Smith // Node neo = getOrCreateNode( "Neo" ); // Node agentSmith = getOrCreateNode( "Agent Smith" ); // // START SNIPPET: shortestPathUsage // PathFinder<Path> finder = GraphAlgoFactory.shortestPath( Traversal.expanderForTypes( KNOWS, Direction.BOTH ), 4 ); // Path foundPath = finder.findSinglePath( neo, agentSmith ); // System.out.println( "Path from Neo to Agent Smith: " + Traversal.simplePathToString( foundPath, NAME_KEY ) ); // END SNIPPET: shortestPathUsage // graphDb.shutdown(); } private static void createChain( String... names ) { for ( int i = 0; i < names.length - 1; i++ ) { Node firstNode = getOrCreateNode( names[i] ); Node secondNode = getOrCreateNode( names[i + 1] ); firstNode.createRelationshipTo( secondNode, KNOWS ); } } private static Node getOrCreateNode( String name ) { Node node = indexService.get( NAME_KEY, name ).getSingle(); if ( node == null ) { node = graphDb.createNode(); node.setProperty( NAME_KEY, name ); indexService.add( node, NAME_KEY, name ); } return node; } private static void registerShutdownHook() { // Registers a shutdown hook for the Neo4j instance so that it // shuts down nicely when the VM exits (even if you "Ctrl-C" the // running example before it's completed) Runtime.getRuntime().addShutdownHook( new Thread() { @SuppressWarnings( "synthetic-access" ) @Override public void run() { System.out.println( "Shutting down database ..." ); graphDb.shutdown(); } } ); } private static void deleteFileOrDirectory( File file ) { if ( file.exists() ) { if ( file.isDirectory() ) { for ( File child : file.listFiles() ) { deleteFileOrDirectory( child ); } } file.delete(); } } } On Thu, Jul 21, 2011 at 3:39 AM, Michael Hunger < [email protected]> wrote: > Caching that result would require synchronizing it with every change using > up memory and performance (at every change) for something that can be > computed > > So far it has not been worth the effort. > > If you really need that value very often you could write a small > TransactionEventHandler that keeps the count updated for the nodes you're > interested in. You would then > ask this handler for the Rel-Count of a node, which would either compute it > (and add/register it to its cache) or just return it from the cache. > > Michael > > Am 20.07.2011 um 21:50 schrieb cyuczi eekc: > > > I guess I was hoping it(size/count) was cached in the database or the > > underlaying database would provide this somehow, ie. in berkeleydb (java > > edition) there's a cursor.count() I could use (though I don't know how > they > > did it implementation-wise) > > > > Thanks! I needed to know that. > > > > On Wed, Jul 20, 2011 at 8:37 PM, Jim Webber <[email protected]> > wrote: > > > >> Hi, > >> > >> Responses from calling the Neo4j APIs are typically lazy, for > performance > >> reasons. So there's no way of eagerly counting the number of > relationships > >> unless you force eager evaluation as you've suggested below. > >> > >> Jim > >> > >> On 20 Jul 2011, at 11:13, cyuczi eekc wrote: > >> > >>> Is there a way to get the number of relationships without having to > >> iterate > >>> through (and count++) them? > >>> ie. rels=firstNode.getRelationships(); > >>> rels.size(); //doesn't actually exist > >>> _______________________________________________ > >>> Neo4j mailing list > >>> [email protected] > >>> https://lists.neo4j.org/mailman/listinfo/user > >> > >> _______________________________________________ > >> Neo4j mailing list > >> [email protected] > >> https://lists.neo4j.org/mailman/listinfo/user > >> > > _______________________________________________ > > Neo4j mailing list > > [email protected] > > https://lists.neo4j.org/mailman/listinfo/user > > _______________________________________________ > Neo4j mailing list > [email protected] > https://lists.neo4j.org/mailman/listinfo/user > _______________________________________________ Neo4j mailing list [email protected] https://lists.neo4j.org/mailman/listinfo/user
