TinkerPop: Generic Query to combine and filter multiple traversals

Question

Conditions:

Is vadas connected to lop within 2 hops
Is vadas connected to peter within 3 hops
Is vadas connected to does-not-exists in 1 hops (a search that wont give any results)

Dummy searches with expected results

Conditions 1 AND 2 => [vadas-marko-lop, vadas-marko-lop-peter]
Conditions 1 OR 3 => [vadas-marko-lop]

What I was able to get

Conditions 1 AND 2

gremlin> g.V().has("person", "name", "vadas").as("from")
.select("from").as("to1").repeat(both().as("to1")).times(2).emit().has("software", "name", "lop")
.select("from").as("to2").repeat(both().as("to2")).times(3).emit().has("person", "name", "peter")
.project("a", "b")
.by(select(all, "to1").unfold().values("name").fold())
.by(select(all, "to2").unfold().values("name").fold())
==>[a:[vadas,marko,lop],b:[vadas,marko,lop,peter]]

Conditions 1 OR 2

gremlin> g.V().has("person", "name", "vadas").as("nodes")
.union(repeat(both().as("nodes")).times(2).emit().has("software", "name", "lop"),
out().has("x", "y", "does-not-exist").as("nodes"))
.project("a")
.by(select(all, "nodes").unfold().values("name").fold())
==>[a:[vadas,marko,lop]]

So how to achieve this I have two different query formats, is there a way to writer a query format that can do both?

And this did not work, anything wrong here? Does not return the nodes that have been traversed

g.V().has("person", "name", "vadas").as("nodes")
.or(
repeat(both().as("nodes")).times(2).emit().has("software", "name", "lop"), 
repeat(both().as("nodes")).times(3).emit().has("person", "name", "peter")
)
.project("a").by(select(all, "nodes").unfold().values("name").fold())
==>[a:[vadas]]
// Expect paths to be printed here vadas..lop, vadas...peter

i can't say i fully follow the problem. what do you mean by "generic"? that seemed to be the big emphasis for your question but it's not clear what that means to me. — stephen mallette, Sep 14 '18 at 16:46
I can mostly achieve `and` and `or` logics with 2 different methods, is there a better way to combine these two? — Srinath Ganesh, Sep 14 '18 at 16:49
i'm still not following. Gremlin has `and()`/`or()` steps for conditional logic, but i don't know what you mean by a "better way to combine these two"? are you saying that you want another way to write the traversals you have above that doesn't use those two steps somehow? — stephen mallette, Sep 14 '18 at 16:56

score 2 · Accepted Answer · answered Sep 16 '18 at 00:26

I don't know if I understand what you're after, but if you just need something like a query template, then maybe this will help:

gremlin> conditions = [
......1>   [filter: {has("software", "name", "lop")},  distance: 2],
......2>   [filter: {has("person", "name", "peter")},  distance: 3],
......3>   [filter: {has("x", "y", "does-not-exist")}, distance: 1]]
==>[filter:groovysh_evaluate$_run_closure1@378bd86d,distance:2]
==>[filter:groovysh_evaluate$_run_closure2@2189e7a7,distance:3]
==>[filter:groovysh_evaluate$_run_closure3@69b2f8e5,distance:1]

gremlin> g = TinkerFactory.createModern().traversal()
==>graphtraversalsource[tinkergraph[vertices:6 edges:6], standard]
gremlin> g.V().has("person", "name", "vadas").
......1>   union(repeat(both().simplePath()).
......2>           times(conditions[0].distance).
......3>           emit().
......4>         filter(conditions[0].filter()).store("x"),
......5>         repeat(both().simplePath()).
......6>           times(conditions[1].distance).
......7>           emit().
......8>         filter(conditions[1].filter()).store("x")).
......9>   barrier().
.....10>   filter(select("x").
.....11>          and(unfold().filter(conditions[0].filter()),
.....12>              unfold().filter(conditions[1].filter()))).
.....13>   path().
.....14>     by("name")
==>[vadas,marko,lop]
==>[vadas,marko,lop,peter]

gremlin> g.V().has("person", "name", "vadas").
......1>   union(repeat(both().simplePath()).
......2>           times(conditions[0].distance).
......3>           emit().
......4>         filter(conditions[0].filter()).store("x"),
......5>         repeat(both().simplePath()).
......6>           times(conditions[2].distance).
......7>           emit().
......8>         filter(conditions[2].filter()).store("x")).
......9>   barrier().
.....10>   filter(select("x").
.....11>          or(unfold().filter(conditions[0].filter()),
.....12>             unfold().filter(conditions[2].filter()))).
.....13>   path().
.....14>     by("name")
==>[vadas,marko,lop]

And a little more abstraction should make it clearer that the two queries only differ in 1 step (and vs or):

apply = { condition ->
  repeat(both().simplePath()).
    times(condition.distance).
    emit().
  filter(condition.filter()).store("x")
}

verify = { condition ->
  unfold().filter(condition.filter())
}

// condition 1 AND 2   
g.V().has("person", "name", "vadas").
  union(apply(conditions[0]),
        apply(conditions[1])).
  barrier().
  filter(select("x").
         and(verify(conditions[0]),
             verify(conditions[1]))).
  path().
    by("name")

// condition 1 OR 3   
g.V().has("person", "name", "vadas").
  union(apply(conditions[0]),
        apply(conditions[2])).
  barrier().
  filter(select("x").
         or(verify(conditions[0]),
            verify(conditions[2]))).
  path().
    by("name")

Thanks a lot, so `filter` has to be done twice, and it seems `or(...as("x"), ...as("y"))` will not store value into `x` and `y`. Am I right? — Srinath Ganesh, Sep 17 '18 at 02:48
Only for current path, which is not helpful in your use-cases as your filter conditions depend on the final result. — Daniel Kuppitz, Sep 17 '18 at 02:53

TinkerPop: Generic Query to combine and filter multiple traversals

1 Answers1