How to cleanly batch queries together in Gremlin - graphql

Question

I am writing a GraphQL resolver that retrieves all vertices by a particular edge using the following query (created returns label person):
software {
created {
name
}
}
Which would resolve to the following Gremlin Query for each software node found:
g.V().hasLabel('software').has('name', 'ripple').in('created')
This returns a result that includes all properties of the object:
{
"result": [
{
"#type": "d",
"#rid": "#24:0",
"#version": 6,
"#class": "person",
"in_knows": [
"#35:0"
],
"name": "josh",
"out_created": [
"#32:0",
"#33:0"
],
"age": 32,
"#fieldTypes": "in_knows=g,out_created=g"
}
],
"dbStats": {
...
}
}
I realize that this will fall foul on GraphQL's N+1 query so i'm trying to batch queries together using a Dataloader pattern. (i'm also hoping to do property selections, so i'm not asking the database to return too much info)
So i'm trying to craft a query like so:
g.V().union(
__.hasLabel('software').has('name', 'ripple').
project('parent', 'child').by('id').
by(__.in('created').fold()),
__.hasLabel('software').has('name', 'lop').
project('parent', 'child').by('id').
by(__.in('created').fold())
)
But this results in the following where the props are missing and it just includes the id of the vertices I want:
{
"result": [
{
"parent": "ripple",
"child": [
"#24:0"
]
},
{
"parent": "lop",
"child": [
"#22:0",
"#23:0",
"#24:0"
]
}
],
"dbStats": {
...
}
}
My Question is, how can I have the Gremlin query return all of the props for the found vertices and none of the other props? Should I even been doing batching this way?

Answer 1

For anyone else reading, the query I was trying to write wouldn't work because the TraversalSet created in the .by(_.in('created') can't be cast from a List to an ElementMap as the stream cardinality wouldn't be enforced. (You can only have one record per row, I think?)
My working query would be to duplicate the keys for each row and specify the props needed (the query below is ok for gremlin 3.3 as used in ODB, otherwise if you've got < gremlin 3.4 replace the last by step with be(elementMap('name', 'age')):
g.V().union(
__.hasLabel('software').has('name', 'ripple').
as('parent').
in('created').as('child').
select('parent', 'child').
by(values('name')).
by(properties('id', 'name', 'age').
group().by(__.key()).
by(__.value())),
__.hasLabel('software').has('name', 'lop').
as('parent').
in('created').as('child').
select('parent', 'child').
by(values('name')).
by(properties('id', 'name', 'age').
group().by(__.key()).
by(__.value()))
)
So that you get a result like this:
{"data": [
{
"parent": "ripple",
"child": {
"id": 5717,
"name": "josh",
"age": 32
}
},
{
"parent": "lop",
"child": {
"id": 5709,
"name": "peter",
"age": 35
}
},
{
"parent": "lop",
"child": {
"id": 5713,
"name": "marko",
"age": 29
}
},
{
"parent": "lop",
"child": {
"id": 5717,
"name": "josh",
"age": 32
}
}
]
}
Which would allow you to create a lookup where you concat all results for "lop" and "ripple" into arrays.