How to return a filled set of vertices with properties?

[Alexandr Porunov]

Hello,

When I traverse vertices JanusGraph returns a set of vertices that isn't filled with properties. When I use next traverse:
List<Vertex> locations = graph.traversal().V().hasLabel("location")
                    .has("location_type", 1)
                    .toList();

I am getting a big set of my locations. But for each vertex where I call value() method, it sends a request to a database to fetch properties. So basically I am getting locations.size() requests to the database:
for(Vertex locationVertex : locations){
    System.out.println("Location id: "+locationVertex.<Integer>value("location_id"));
}

Is it possible to fetch a set of vertices with filled properties in one request?

Best regards,
Alexandr

[Daniel Kuppitz]

Here are a few alternatives:

g.V().has("location","location_type",1).values("location_id")        // if you only need the location_id values

g.V().has("location","location_type",1).valueMap("location_id",...)  // if you only need a few more values, but not all

g.V().has("location","location_type",1).values("location_id")        // if you need all property values

g.V().has("location","location_type",1).values(true)                 // if you also need the vertex id

The first traversal will return a list of Integers, all others a list of maps.

Cheers,

Daniel

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[Alexandr Porunov]

Hello Daniel,

Thanks for the advice. Is it possible to fetch vertices filled with properties? Or maybe there is a method which can get get values map and fill vertices?
I just need to get vertices from the database which are already filled with values because I use those vertices to convert them to ORM objects.

Best regards,
Alexandr

On Thursday, March 29, 2018 at 9:07:35 PM UTC+3, Daniel Kuppitz wrote:

Here are a few alternatives:

g.V().has("location","location_type",1).values("location_id")        // if you only need the location_id values

g.V().has("location","location_type",1).valueMap("location_id",...)  // if you only need a few more values, but not all

g.V().has("location","location_type",1).values("location_id")        // if you need all property values

g.V().has("location","location_type",1).values(true)                 // if you also need the vertex id

The first traversal will return a list of Integers, all others a list of maps.

Cheers,

Daniel

On Thu, Mar 29, 2018 at 10:42 AM, Alexandr Porunov <alexandr...@gmail.com> wrote:

Hello,

When I traverse vertices JanusGraph returns a set of vertices that isn't filled with properties. When I use next traverse:
List<Vertex> locations = graph.traversal().V().hasLabel("location")
                    .has("location_type", 1)
                    .toList();

I am getting a big set of my locations. But for each vertex where I call value() method, it sends a request to a database to fetch properties. So basically I am getting locations.size() requests to the database:
for(Vertex locationVertex : locations){
    System.out.println("Location id: "+locationVertex.<Integer>value("location_id"));
}

Is it possible to fetch a set of vertices with filled properties in one request?

Best regards,
Alexandr

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[Daniel Kuppitz]

The fastest way in Titan was a MultiQuery, if I remember correctly, but it seems like it's deprecated in JanusGraph: https://static.javadoc.io/org.janusgraph/janusgraph-core/0.1.1/org/janusgraph/core/JanusGraphMultiVertexQuery.html

Thus I'm not really sure what the recommendation is for JanusGraph.

Cheers,

Daniel

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[Alexandr Porunov]

Daniel,

You are a life saver! Thank you very much for the help!
I don't know why it is deprecated in JanusGraph but it really works like I need.
Here is what I did:

List<Vertex> locations = graph.traversal().V().hasLabel("location").has("location_type", 3).next(50000);
graph.multiQuery().addAllVertices(locations).properties();
Integer myId = locations.get(123).<Integer>value("location_id"); // Properties are returned immediately without network calls.

Thank you very much again.

Best regards,
Alexandr

[Misha Brukman]

Hi Daniel,

I see @Deprecated markers in StandardJanusGraphTx#multiQuery(), however, those were added in April 2015, which means it was added to Titan, and were simply brought over to JanusGraph.

What would you suggest we should do here?

Misha

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[Daniel Kuppitz]

I don't know or don't remember what the plan was, but if the Janus devs think it's a good implementation, then just un-deprecate it..? :)

Cheers,

Daniel

[HadoopMarc]

Hi Misha,

As remarked earlier here, my guess is that the MultiQuery API is deprecated because of replacement by:

https://static.javadoc.io/org.janusgraph/janusgraph-core/0.2.0/org/janusgraph/graphdb/query/vertex/MultiVertexCentricQueryBuilder.html

It would be useful, though, to have:
 - a section in the JanusGraph ref docs about the MultiVertexCentricQuery
 - some pointers in the deprecated API towards the new one

Cheers,    Marc

Op zondag 1 april 2018 04:59:16 UTC+2 schreef Daniel Kuppitz:

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[Misha Brukman]

Thanks, Marc! I filed https://github.com/JanusGraph/janusgraph/issues/984 to track this task.

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[chris....@gmail.com]

I started to write up the fix for this and I don't think MultiVertexCentricQueryBuilder is replacement method since JanusGraphMultiVertexQuery is dependent on it and it came out in early 2014. 

lines 1031-1045 of janusgraph-core/src/main/java/org/janusgraph/graphdb/transaction/StandardJanusGraphTx.java

    @Override

    @Deprecated

    public JanusGraphMultiVertexQuery multiQuery(JanusGraphVertex... vertices) {

        MultiVertexCentricQueryBuilder builder = new MultiVertexCentricQueryBuilder(this);

        for (JanusGraphVertex v : vertices) builder.addVertex(v);

        return builder;

    }

    @Override

    @Deprecated

    public JanusGraphMultiVertexQuery multiQuery(Collection<JanusGraphVertex> vertices) {

        MultiVertexCentricQueryBuilder builder = new MultiVertexCentricQueryBuilder(this);

        builder.addAllVertices(vertices);

        return builder;

    }

I spent about an hour digging and found a vague reference that the replacement should be available in titan 1.0 https://github.com/thinkaurelius/titan/issues/1037, but I couldn't fine anything in the titan PRs or gremlin change notes. If there's no existing replacement and no current plans implement a replacement would it make sense to just un-deprecate it? aka +1 to Daniel's post.

[Ted Wilmes]

I added my two cents on this topic up at https://github.com/JanusGraph/janusgraph/issues/984. I'm in agreement that it should be un-deprecated.

--Ted