Gremlin query uneven result issue

Question

Suppose I have 3 students (A,B,C) and having a major subject and marks respectievely but when I query the result shown in a uneven way.

Data

A -> Math -> 77

B -> History -> 70

C -> Science -> 97

Query

g.V('Class').has('name',within('A','B','C'))

Result

{"student_name":['A','B','C'], "major_subject":['Math','Science','History'], "marks":[70,77,97]}

The data displayed by querying the database is not in order according to the name of the student.

Answer 1

I assume that your graph looks kinda like this:

g = TinkerGraph.open().traversal()
g.addV('student').property('name', 'A').
    addE('scored').to(addV('subject').property('name', 'Math')).
      property('mark', 77).
  addV('student').property('name', 'B').
    addE('scored').to(addV('subject').property('name', 'History')).
      property('mark', 70).
  addV('student').property('name', 'C').
    addE('scored').to(addV('subject').property('name', 'Science')).
      property('mark', 97).iterate()

Now the easiest way to gather the data is this:

gremlin> g.V().has('student', 'name', within('A', 'B', 'C')).as('student').
           outE('scored').as('mark').inV().as('major').
           select('student','major','mark').
             by('name').
             by('name').
             by('mark')
==>[student:A,major:Math,mark:77]
==>[student:B,major:History,mark:70]
==>[student:C,major:Science,mark:97]

But if you really depend on the format shown in your question, you can do this:

gremlin> g.V().has('student', 'name', within('A', 'B', 'C')).
           store('student').by('name').
           outE('scored').store('mark').by('mark').
           inV().store('major').by('name').
           cap('student','major','mark')
==>[major:[Math,History,Science],student:[A,B,C],mark:[77,70,97]]

If you want to get the cap'ed result to be ordered by marks, you'll need a mix of the 2 queries:

gremlin> g.V().has('student', 'name', within('A', 'B', 'C')).as('a').
           outE('scored').as('b').
           order().
             by('mark').
           inV().as('c').
           select('a','c','b').
             by('name').
             by('name').
             by('mark').
           aggregate('student').by(select('a')).
           aggregate('major').by(select('b')).
           aggregate('mark').by(select('c')).
           cap('student','major','mark')
==>[major:[History,Math,Science],student:[B,A,C],mark:[70,77,97]]

To order by the order of inputs:

gremlin> input = ['C', 'B', 'A']; []
gremlin> g.V().has('student', 'name', within(input)).as('a').
           order().
             by {input.indexOf(it.value('name'))}.
           outE('scored').as('b').
           inV().as('c').
           select('a','c','b').
             by('name').
             by('name').
             by('mark').
           aggregate('student').by(select('a')).
           aggregate('major').by(select('b')).
           aggregate('mark').by(select('c')).
           cap('student','major','mark')
==>[major:[97,70,77],student:[C,B,A],mark:[Science,History,Math]]