Just make sure that it is just a snapshot of the data and doesn't update its caches.
Otherwise you will run into synchronization issues. See also this thread and Tobias' explanations around it: http://neo4j-community-discussions.438527.n3.nabble.com/Neo4j-Synchronization-of-EmbeddedReadOnlyGraphDatabase-Bug-td3174626.html#a3213450 Michael Am 23.11.2011 um 15:05 schrieb Vinicius Carvalho: > But wouldn't it mean that I need to have exclusive lock on the db? I would > like to keep the server running pointing at the same data directory. > > Regards > > On Wed, Nov 23, 2011 at 1:50 PM, Michael Hunger < > michael.hun...@neotechnology.com> wrote: > >> Please use EmbeddedGraphDatabase, >> >> EmbeddedReadOnlyGraphDatabase caches a snapshot of the data in its caches >> and doesn't get update-changes. >> >> Michael >> >> Am 23.11.2011 um 14:39 schrieb Vinicius Carvalho: >> >>> Hi Michael, thanks. The data load was fine, I've used your script with >> the >>> BathInserter. Memory footprint was really slow, I think the peak was >> 200mb >>> of heap usage. I did something really retarded and left a logger.info, >>> which slowed things a bit, but the process was really smooth. >>> >>> Many thanks on the help with the query. I'll try this, I'm putting the >>> readonlyembedded neo inside our app right now. I expect to see some good >>> performance boost :) >>> >>> Best Regards >>> >>> On Wed, Nov 23, 2011 at 12:12 PM, Michael Hunger < >>> michael.hun...@neotechnology.com> wrote: >>> >>>> Vinicius, >>>> >>>> first: did you have any issues importing the data into Neo4j? >>>> second: your example used cypher which is not optimized for performance >>>> (yet!). This is in our plans for the next two releases of neo4j. >>>> >>>> So if you want to see the real performance of neo4j, please use the >>>> traversal framework or the core-API: >>>> >>>> Cypher & Traversals: >>>> >>>> // define >>>> cypherQuery = cypherParser.parse("start n=node({start_node}) match >>>> n-->()-->x return x") >>>> traversalQuery = >>>> >> Traversal.description().evaluator(Evaluators.atDepth(2)).expand(Traversal.expanderForAllTypes(Direction.OUTGOING)) >>>> >>>> // execute >>>> for (Node n : cypherQuery.execute({"start_node":startNode})) { ... } >>>> for (Node n : traversalQuery.traverse(startNode).nodes()) { ... } >>>> >>>> If you're interested in the paths, remove the ".nodes()" call at the >>>> traverser >>>> >>>> In java core-api code: >>>> >>>> Node start=db.getNodeById(3); >>>> >>>> for (Relationship rel=start.getRelationships()) { >>>> Node second = rel.getOtherNode(start); >>>> for (Relationship rel=second.getRelationships()) { >>>> Node third = rel.getOtherNode(second); >>>> // do something with the 3 nodes, 2 relationships which form your >>>> path >>>> } >>>> } >>>> >>>> In the REST API the traversal would look like: (see >>>> >> http://docs.neo4j.org/chunked/snapshot/rest-api-traverse.html#rest-api-traversal-using-a-return-filter >>>> ) >>>> * POST http://localhost:7474/db/data/node/3/traverse/node >>>> * Accept: application/json >>>> * Content-Type: application/json >>>> >>>> { >>>> "relationships" : [ {"direction" : "out" } ], >>>> "max_depth" : 3 >>>> } >>>> >>>> >>>> Am 23.11.2011 um 11:54 schrieb Vinicius Carvalho: >>>> >>>>> Hi there, I've posted a few days ago about the POC I'm doing here at my >>>>> company. I have some initial numbers and I'd like to ask for some help >>>> here >>>>> in order to promote neo4j here in LMI Ericsson. >>>>> >>>>> I've loaded a mySQL db with a really simple entity, that pretty much >> only >>>>> represents a node and relations (only properties it has is an UID and >> x/y >>>>> space coordinate for each node) >>>>> >>>>> The DB contains 250.000 cells and 19. relations stored in a myISAM >> table, >>>>> indexed only by it's primary key. Please find the DDL for the two >> tables. >>>>> >>>>> CREATE TABLE `pci`.`cells` ( >>>>> `id` varchar(32) collate utf8_bin NOT NULL, >>>>> `x_pos` double default NULL, >>>>> `y_pos` double default NULL, >>>>> `pci` smallint(6) default '0', >>>>> PRIMARY KEY (`id`) >>>>> ) >>>>> >>>>> CREATE TABLE `pci`.`relations` ( >>>>> `id` int(11) NOT NULL auto_increment, >>>>> `source` varchar(32) collate utf8_bin default NULL, >>>>> `target` varchar(32) collate utf8_bin default NULL, >>>>> PRIMARY KEY (`id`), >>>>> KEY `src_idx` (`source`), >>>>> KEY `src_target` (`target`) >>>>> ) >>>>> >>>>> So as you can see, a simple secondary table contains the relationship >>>> with >>>>> source and targets pointing to the cells table. >>>>> >>>>> I've loaded this exact same DB into a neoserver running on the same >>>>> machine: A Blade with 26 cpus (6 cores each) and 16gb RAM. >>>>> >>>>> One of the requirements we have is to find all associations of my >>>>> associations. Something that in neo I did like this: >>>>> >>>>> START n = node(3) >>>>> MATCH n-->()-->(x) >>>>> return x >>>>> >>>>> For this specific node it returns 6475 nodes. >>>>> >>>>> I have tested this before using Hibernate in two modes: without a L2 >>>> cache, >>>>> and with an L2 Cache (Ehcache standalone no replication). >>>>> Here's a snippet of the code that loads it, so you can understand >> what's >>>>> going under the hood: >>>>> >>>>> >>>>> @Override >>>>> public List<Cell> loadCellWithRealtions(String... ids) { >>>>> Session session = (Session) em.getDelegate(); >>>>> Criteria c = session.createCriteria(Cell.class) >>>>> .setFetchMode("incomingRelations", FetchMode.SELECT) >>>>> .setFetchMode("outgoingRelations", FetchMode.SELECT) >>>>> .add(Restrictions.in("id", Arrays.asList(ids))); >>>>> List<Cell> results = c.list(); >>>>> for(Cell cell : results){ >>>>> Hibernate.initialize(cell.getIncomingRelations()); >>>>> Hibernate.initialize(cell.getOutgoingRelations()); >>>>> } >>>>> return results; >>>>> } >>>>> >>>>> @Override >>>>> public List<Cell> loadCellWithNeighbourRelations(String... ids) { >>>>> List<Cell> cells = loadCellWithRealtions(ids); >>>>> for(Cell c : cells){ >>>>> for(Relation r : c.getIncomingRelations()){ >>>>> Hibernate.initialize(r.getSource().getIncomingRelations()); >>>>> Hibernate.initialize(r.getSource().getOutgoingRelations()); >>>>> } >>>>> for(Relation r : c.getOutgoingRelations()){ >>>>> Hibernate.initialize(r.getTarget().getIncomingRelations()); >>>>> Hibernate.initialize(r.getTarget().getOutgoingRelations()); >>>>> } >>>>> } >>>>> return cells; >>>>> } >>>>> >>>>> >>>>> >>>>> So the first method executes one query and 2 subselects to find a cell >>>> and >>>>> all relations, the second method, iterate over each relation and do the >>>>> same. So I pretty much will have something like 3+r*3 selects on db, >>>> where >>>>> r is the number of relations right. >>>>> >>>>> Ok, to be a bit fair with the tests, I've ran this for the same node 10 >>>>> times (get a chance to warm the caches), exclude the longest and >> smallest >>>>> result, and then took a mean of it. Here's the results: >>>>> >>>>> EhCache: 70ms >>>>> Plain Hibernate: 550ms >>>>> >>>>> I still don't have a version of neo4j code running integrated in the >> app >>>>> server, but the idea is to use REST API. Running the query on the REST >>>> API >>>>> took over 2 seconds on average, but due the large size of the response, >>>>> network lagging was the issue. So I ran the same query 10 times using >> the >>>>> web console, and the average time for neo was 300ms >>>>> >>>>> Before asking anything I do know that we will have more complex queries >>>>> where neo will shine, but I need to improve those results in order to >>>> sell >>>>> it here :), with those numbers, ppl will just say that having a cache >> and >>>>> using Relational model would suffice. >>>>> >>>>> Anything I could do to improve this? >>>>> >>>>> Regards >>>>> _______________________________________________ >>>>> Neo4j mailing list >>>>> User@lists.neo4j.org >>>>> https://lists.neo4j.org/mailman/listinfo/user >>>> >>>> _______________________________________________ >>>> Neo4j mailing list >>>> User@lists.neo4j.org >>>> https://lists.neo4j.org/mailman/listinfo/user >>>> >>> _______________________________________________ >>> Neo4j mailing list >>> User@lists.neo4j.org >>> https://lists.neo4j.org/mailman/listinfo/user >> >> _______________________________________________ >> Neo4j mailing list >> User@lists.neo4j.org >> https://lists.neo4j.org/mailman/listinfo/user >> > _______________________________________________ > Neo4j mailing list > User@lists.neo4j.org > https://lists.neo4j.org/mailman/listinfo/user _______________________________________________ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
