accessing subgraph vertices and edges

[Burak Arikan]

Hi Darrick, 

I am using pacer (1.1.1 java), pacer-neo4j (2.1.0 java) on jruby 1.7.0. 

In the past versions of Pacer there used to be vertices and edges method for subgraph, but now they seem to be gone... What are the new methods to access to vertices and edges in a generated subgraph? 

subgraph = friend.out_e('follows').in_v.out_e('follows').in_v.subgraph

=> #<PacerGraph tinkergraph[vertices:7 edges:8]

subgraph.vertices

NoMethodError: undefined method `vertices' for #<PacerGraph tinkergraph[vertices:7 edges:8]

from (irb):42:in `evaluate'

from org/jruby/RubyKernel.java:1065:in `eval'

from org/jruby/RubyKernel.java:1390:in `loop'

from org/jruby/RubyKernel.java:1173:in `catch'

from org/jruby/RubyKernel.java:1173:in `catch'

from /Users/arikan/.rvm/gems/jruby-1.7.0/gems/railties-3.2.8/lib/rails/commands/console.rb:47:in `start'

from /Users/arikan/.rvm/gems/jruby-1.7.0/gems/railties-3.2.8/lib/rails/commands/console.rb:8:in `start'

from /Users/arikan/.rvm/gems/jruby-1.7.0/gems/railties-3.2.8/lib/rails/commands.rb:41:in `(root)'

from org/jruby/RubyKernel.java:1019:in `require'

from script/rails:6:in `(root)'

Burak

[Burak Arikan]

So I got it, subgraph.v and subgraph.e works to get the elements respectively. I guess longer methods removed for api consistency. 

[Burak Arikan]

But inrelation to this question. The basic access to the id of the vertice is not the same as it used to be. 

subgraph.e[0].in_v.id

undefined method `id' for #<GraphE -> E-Range(0..0) -> inV>

from (irb):84:in `evaluate'

from org/jruby/RubyKernel.java:1065:in `eval'

from org/jruby/RubyKernel.java:1390:in `loop'

from org/jruby/RubyKernel.java:1173:in `catch'

from org/jruby/RubyKernel.java:1173:in `catch'

from /Users/arikan/.rvm/gems/jruby-1.7.0/gems/railties-3.2.8/lib/rails/commands/console.rb:47:in `start'

from /Users/arikan/.rvm/gems/jruby-1.7.0/gems/railties-3.2.8/lib/rails/commands/console.rb:8:in `start'

from /Users/arikan/.rvm/gems/jruby-1.7.0/gems/railties-3.2.8/lib/rails/commands.rb:41:in `(root)'

from org/jruby/RubyKernel.java:1019:in `require'

from script/rails:6:in `(root)'

subgraph.e[0].in_v[:id]

nil

[Darrick Wiebe]

Hi Burak,

Try vertex.element_id or g.v.element_ids. It's the same for edges, too.

I changed it because the old one was causing me name conflicts.

Cheers,

Darrick

[Burak Arikan]

hmm got it, so this works: 

subgraph.v.each {|n| puts n.element_id}

I think for API consistency this should work as well, it currently returns nil.

g.v.each {|n| puts n[:id]} 

Burak

[Darrick Wiebe]

I'll give that some thought. It would be handy in some cases, but it's worth noting that in Neo4j and OrientDB, element IDs are implementation details that really shouldn't be messed with too much. For instance, in Neo4j, IDs are recycled if an element is deleted, while in Orient, ids are some sort of special object.

It actually bugs me a little bit that Blueprints reserves the id property from being used for modelling data and I'm actually tempted to work around that limitation in Pacer, rather than make id a special read-only property...

Darrick

[Burak Arikan]

Now I got a different value type when using element_ids with an individual edge. Did not get the class value, how can we get the element id from it? Thanks.

>> subgraph.e[0].in_v.element_ids

"48"

Total: 1

=> #<GraphE -> E-Range(0..0) -> inV -> Obj(Java::ComTinkerpopGremlinPipesTransform::IdPipe)>

>> subgraph.e.to_a.each {|e| puts e.in_v.element_ids}

#<#<Class:0x4dbad3b1>:0x6bca69a5>

#<#<Class:0x4dbad3b1>:0x5e36ba3b>

#<#<Class:0x4dbad3b1>:0xc845640>

#<#<Class:0x4dbad3b1>:0x79b9048d>

#<#<Class:0x4dbad3b1>:0x55c8a526>

#<#<Class:0x4dbad3b1>:0xb2cfc7e>

#<#<Class:0x4dbad3b1>:0x3652ac26>

#<#<Class:0x4dbad3b1>:0x3636c89d>

=> [#<E[146]:57-follows-48>, #<E[147]:57-follows-55>, #<E[375]:96-follows-59>, #<E[148]:57-follows-53>, #<E[374]:96-follows-57>, #<E[376]:96-follows-55>, #<E[660]:142-follows-57>, #<E[661]:142-follows-96>]

Burak

[Darrick Wiebe]

That's just because you're printing the routes rather than the values the routes would produce. The following should do the trick:

subgraph.e.to_a.each {|e| puts e.in_v.element_ids.to_a}

Cheers,

Darrick