Graphql-ruby: Adding Relay Connections for pagination slows down responses 10x

[cappyccino]

Context

I have a functioning GraphQL API using graphql-ruby and graphql-batch. I'm using Sequel for database connections. I wanted to try out the built-in pagination functionality according to the docs here.

However, changing my field to be a connection, (keeping everything else the exact same), my queries take almost ten times longer to complete.

Is there any way to optimize this?

Code Comparisons

Original Pagination Implementation

Code:

field :things, types[Types::Thing] do
  description "List of things"
  argument :limit, types.Int, "Limit the number of results, default 100", default_value: 100

  resolve -> (_obj, args, _ctx) {
    DB::Things.first(args[:limit])
  }
end

Query:

{
  things(limit: 1000) {
    thingField1
    thingField2
    nestedThing {
      nestedThingField1
      nestedThingField2
    }
  }
}

Average response time: 1,300ms

Pagination Implementation with Connections

Code:

connection :things, Types::Thing.connection_type do
  description "List of things"
  resolve -> (_obj, _args, _ctx) {
    DB::Things.all
  }
end

Query:

{ 
 things(first: 1000) {
    edges {
      node {
        thingField1
        thingField2
        nestedThing {
          nestedThingField1
          nestedThingField2
        }
      }
    }
  }
}

Average response time: 10,100ms

[rmosolgo]

Hi! Yikes!

Can you see any difference in the underlying SQL queries?

For example, I noticed that you added a .all in DB::Things.all. Does that load every record in the table? I bet that would slow it down a lot!

I think you could try removing the .all, and let graphql-ruby's built-in Sequel support perform pagination for you. How does that work for you?

[cappyccino]

Yeah, it's definitely not limiting in the Sequel query 😕
Old code: SELECT * FROM "things" LIMIT 1000
New code: SELECT * FROM "things"

How do I go about getting the connection to work without all? Changing the code to this:

connection :things, Types::Thing.connection_type do
  description "List of things"
  resolve -> (_obj, _args, _ctx) {
    DB::Thing
  }
end

gives me a RuntimeError (No connection implementation to wrap Class (DB::Thing)).

Changing it to not have a custom resolver:

connection :things, Types::Thing.connection_type,
  description: "List of things"

gives me a NoMethodError (undefined method 'things' for nil:NilClass)

Am I missing something?

[rmosolgo]

Hmm, I don't know Sequel too well so it's probably my bad. We need to get a Sequel::Dataset somehow, maybe the .dataset method would do the trick? DB::Thing.dataset? I got the example from: http://sequel.jeremyevans.net/rdoc/classes/Sequel/Model/DatasetMethods.html

[cappyccino]

Ah perfect, that was it!! Average query times are back to normal.

Thanks so much for your help! Closing the issue.

[rmosolgo]

👏 🙌 Glad to hear it, thanks for such a detailed issue!