Gremlin（Titan）中的嵌套变换

Question

I have a graph with two vertexes with a key called 'type'.

Why the following:

g.V("type", "language").transform { language_1 ->
  1+1;
}

returns:

==>2
==>2

and the following:

g.V("type", "language").transform { language_1 ->
  g.V("type", "language").transform { language_2 ->
    1+1;
  }
}

returns:

==>[GremlinStartPipe, GraphQueryPipe(has,vertex), IdentityPipe, TransformFunctionPipe]
==>[GremlinStartPipe, GraphQueryPipe(has,vertex), IdentityPipe, TransformFunctionPipe]

?

Answer 1

What you are seeing in the second example is the String representation of a pipeline. Both of your example queries return pipelines, but when the Gremlin console sees a pipeline returned it automatically reads all the data out of it and displays it. If you wish to use the data returned from a nested pipeline within a larger query as you do in the second query, you must explicitly read the data. Try this:

g.V("type", "language").transform { language_1 ->
  g.V("type", "language").transform { language_2 ->
    1+1;
  }.next()
}