Graphql-ruby: Access Posgres' JSONB columns

[benoror]

Hi! How can I include JSONB attributes (using PostgreSQL) in my GraphQL Schema?

In my Rails app I usually access those column using store_accessor:

store_accessor :jsonb_column, :prop_a, :prop_b

Disclaimer: I'm new to GraphQL 🙈

Thanks!

[rmosolgo]

Does store_accessor make a method with the same name? If so, then you don't need anything special, just add a field, eg

field :prop_a, types.String # or types.Int, whatever type is in that field

[benoror]

@rmosolgo mmm good point, I should have omitted the store_accesor stuff, since what I'm looking for is to keep it as a nested record. For example:

# person_type.rb
module Graph
  PersonType = GraphQL::ObjectType.define do
    name 'Person'
    description 'A person'

    field :id, types.ID
    field :medical_records do # this is the JSONB column
      type MedicalRecordsType
      resolve lambda { |obj, _args, _ctw|
        obj.medical_records
      }
    end
  end
end

# medical_records_type.rb
module Graph
  MedicalRecordsType = GraphQL::ObjectType.define do
    name 'MedicalRecords'
    description 'A medical records'

    field :diabetes, types.String
    # ... other regular fields
  end
end

If I try to run the following query:

query: {
  person(id: 1) {
    medical_records { 
      diabetes 
    }
  }
}

I get the following Exception:

NoMethodError in Api::V1::GraphController#index

undefined method `diabetes' for #<Hash:0x007fe143e36878>

[rmosolgo]

Oh I see!

By default, fields perform a method call. To resolve a field with [...], You can specify a key with hash_key:, eg,

field :diabetes, types.String, hash_key: :diabetes 
# will find a value by doing `medical_records[:diabetes]`

A few more examples here: http://www.rubydoc.info/gems/graphql/GraphQL/Field

Does that work for you? Please reopen this if not!

[benoror]

@rmosolgo awesome! It worked like a charm for 1-level nested fields, but it stops working for deeply nested fields:

# medical_records_type.rb
module Graph
  MedicalRecordsType = GraphQL::ObjectType.define do
    name 'MedicalRecords'
    description 'A medical records'

    field :diabetes, types.String

    # Option A
    field :measurements, types[MeasurementsType], hash_key: :measurements

    # Option B
    field :measurements do
      type MeasurementsType
      resolve lambda { |obj, _args, _ctw|
        obj['measurements']
      }
    end
  end
end

# measurements_type.rb
module Graph
  MeasurementsType = GraphQL::ObjectType.define do
    name 'Measurements'
    description 'A measurements'

    field :weight, types.Integer
    field :height, types.Integer
  end
end

[rmosolgo]

Can you help me understand what "stops working" means here? Is there runtime error?

[benoror]

@rmosolgo sorry, I sent the comment before finishing it (freaking CMD + Enter). I updated the code above ☝️

Basically the issue is with the resulting repsonse:

Option A will return: measurements: null

Option B will return: measurements: {weight: null, height: null}

...while the actual value in the JSONB record being: measurements: {weight: 100, height: 70}

[rmosolgo]

Option A has

field :measurements, types[MeasurementsType]

which means that measurements returns a _list_ of MeasurementsType objects. Should it be

field :measurements, MeasurementsType

which means it returns an object of type MeasurementsType? (This would match Option B.)

[benoror]

@rmosolgo good catch, this was indeed a newbie mistake. Although neither results changed at all for some reason

Option A will return: measurements: null

Option B will return: measurements: {weight: null, height: null}

[rmosolgo]

Oh right, the other difference is:

# Access a key named `:measurements` (symbol) 
field :measurements, types[MeasurementsType], hash_key: :measurements
# Access a key named `"measurements"` (string)
field :measurements, types[MeasurementsType], hash_key: "measurements"

Does it work for you if you specify a string as the key (hash_key: "measurements")?

Judging by the docs, ActiveRecord::Store accepts _either_ strings or symbols, but I imagine that after the first key, it's up to you to choose the right kind of key. And if the storage is JSON, the keys are probably strings!

Any luck?

[benoror]

@rmosolgo yeah that did the trick!

thanks a lot for the help 😸 u're awesome!