I should probably mention that I am using neo4j community (embedded) latest sources up to date from github
On Thu, Jul 21, 2011 at 4:59 AM, cyuczi eekc <[email protected]> wrote: > 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
