Parsing Apollo GraphQL query into Sequelize query with include and attributes fields

Question

I'm working with Apollo, building resolvers for my GraphQL requests.

To be efficient I want to get a list of models requested (with respective nesting) and the fields requested from each of these models. That way I can pass this information to sequelize to only join the models when required - and only pull the fields necessary.

Resolvers do pass this information on in the info object.

(obj, args, { models }, info) => ...

From the info object the fields, nested models and their respective selected fields are exposed through this path:

info.fieldNodes[0].selectionSet.selections

My problem is parsing this structure (in some sort of recursive manner I imagine) into a sensible structure for me to pass into sequelize queries.

An example GraphQL query:

{
  getCompany(id: 1) {
    id
    name
    companyOffices {
      id
      users {
        id
        title
        userLinks {
          id
          linkUrl
        }
      }
    }
  }
}

Which generates the following on info.fieldNodes[0].selectionSet.selections (pruning some fields for the sake of brevity):

[
   {
      "kind":"Field",
      "name":{
         "kind":"Name",
         "value":"id"
      }
   },
   {
      "kind":"Field",
      "name":{
         "kind":"Name",
         "value":"name"
      }
   },
   {
      "kind":"Field",
      "name":{
         "kind":"Name",
         "value":"companyOffices"
      },
      "selectionSet":{
         "kind":"SelectionSet",
         "selections":[
            {
               "kind":"Field",
               "name":{
                  "kind":"Name",
                  "value":"id"
               }
            },
            {
               "kind":"Field",
               "name":{
                  "kind":"Name",
                  "value":"users"
               },
               "selectionSet":{
                  "kind":"SelectionSet",
                  "selections":[
                     {
                        "kind":"Field",
                        "name":{
                           "kind":"Name",
                           "value":"id"
                        }
                     },
                     {
                        "kind":"Field",
                        "name":{
                           "kind":"Name",
                           "value":"title"
                        }
                     },
                     {
                        "kind":"Field",
                        "name":{
                           "kind":"Name",
                           "value":"userLinks"
                        },
                        "selectionSet":{
                           "kind":"SelectionSet",
                           "selections":[
                              {
                                 "kind":"Field",
                                 "name":{
                                    "kind":"Name",
                                    "value":"id"
                                 }
                              },
                              {
                                 "kind":"Field",
                                 "name":{
                                    "kind":"Name",
                                    "value":"linkUrl"
                                 }
                              }
                           ]
                        }
                     }
                  ]
               }
            }
         ]
      }
   }
]

Using this information I want to generate a query like the following:

  const company = await models.Company.findOne({
    where: { id: args.id },
    attributes: // DYNAMIC BASED ON QUERY
    include: // DYNAMIC BASED ON QUERY
  });

So I need to parse the GraphQL query above down to this something like this structure from the above info object:

{
  attributes: ["id", "name"],
  include: [
    {
      model: "companyOffices",
      attributes: ["id"],
      include: [
        {
          model: users,
          attributes: ["id", "title"],
          include: [{ model: "userLinks", attributes: ["id", "linkUrl"] }]
        }
      ]
    }
  ]
};

But I'm unclear how to achieve this with recursion without things getting messy. If there's an easier way of achieving this dynamic include / attributes I'm open to that too.

tl;dr - how can I transfer the models and fields of an Apollo GraphQL query into the include and attributes of a sequelize query?

Answer 1

It may be skirting the issue but I wonder if something like graphql-sequelize could help with something like this. If not I've used this strategy to accomplish the attributes piece of your question.

const mapAttributes = (model, { fieldNodes }) => {
  // get the fields of the Model (columns of the table)
  const columns = new Set(Object.keys(model.rawAttributes));
  const requested_attributes = fieldNodes[0].selectionSet.selections
    .map(({ name: { value } }) => value);
  // filter the attributes against the columns
  return requested_attributes.filter(attribute => columns.has(attribute));
};

User: async (
    _, // instance (not used in Type resolver)
    { username, ... }, // arguments 
    { models: { User }, ... }, // context
    info,
  ) => {
    if (username) {  
      // (only requested columns queried)
      return User.findOne({
        where: { username },
        attributes: mapAttributes(User, info),
      });
    } ... 
  }

Answer 2

I finally got a solution to this problem (kinda).

const mapAttributes = (projectors, models) => {
    const map = {};
    const set = [];
    Object.keys(projectors).forEach((projector) => {
        if (typeof projectors[projector] === 'object') {
            map[projector] = mapAttributes(projectors[projector], models.slice(1));
        } else {
            set.push(projector);
            map[models[0]] = set;
        }
    });
    return map;
};

here projectors is the object notation of graphql schema, same like the object we get from info.fieldNodes[0].selectionSet.selections

and models, is the orderly way of iteration. so in the example above it'll be like

['company', 'companyOffices', 'users'] etc.

From the final map we get into a neat structure from which we good get the attributes.

And finally when you are returning the argument, you may need to convert the sequelize output into graphql type

const sequelizeToGraphql = (results = [], vouchers = [], postings = []) => {
    const final = { particulars: [] };
    results.forEach((result) => {
        vouchers.forEach((voucher) => {
            final[voucher] = result[voucher];
        });
        const obj = {};
        postings.forEach((posting) => {
            obj[posting] = result[`posting.${posting}`];
        });
        final.particulars.push(obj);
    });
    return final;
};

Here vouchers and postings are the table name for me in my sequqlize, similarly make changes for yourself