Gremlin Support in DGraph

[mrjn (Manish R Jain)]

@janardhan

g.v(1).inE(‘friend’); // incoming friend edges

We can do all of the rest, but can’t do this one. We don’t automatically generate reverse edges. So, we can’t do inE.

@janardhan

g.V.has(‘email’, null) // people who don’t have email addresses

We also can’t do this. To check for negations require looking through everything, which isn’t a possibility in a scalable system.

@janardhan

Gremlin/Cypher allows you to specify such queries which we can’t do in graphQL.
Recipes

g.V(1).repeat(out().simplePath()).until(hasId(5)).path().limit(1)
The traversal starts at vertex with the identifier of “1” and repeatedly traverses on out edges “until” it finds a vertex with an identifier of “5”.

Yeah. Finding shortest path would need to be added to our version of GraphQL. Had a chat with the author of GraphQL, Lee Byron, and I think we’ll definitely have to extend and modify GraphQL for our usage. So, we could borrow concepts from both Gremlin and Cypher to make such things happen.

@janardhan

Gremlin also supports declarative form of query in addition to imperative form.
example: “Who created a project named ‘lop’ that was also created by someone who is 29 years old? Return the two creators.”

The schematics of the query is a bit weird. Both the in and the out are named created. But, this is something we can do with our existing system.

@janardhan

All the graph languages supported by gremlin get converted to gremlin bytecode which is executed by gremlin VM.

Interesting. So, this gremlin VM, is essentially Java based, and requires to be run as a Java program, yeah?

Very interesting thread! Trying to understand the options here. I think we should have a chat, sometime soon – so I can understand this better.

Overall, sounds like you made good progress! Nice work!