Share dataloader between loadable objectFields

[alexandernanberg]

So far I've not found a way to avoid making duplicate db queries when adding aliases/conveniences fields that depend on another field. E.g.

query MyQuery {
  viewer {
    email
    memberships {
      edges {
        node {
          org {
            name
          }
        }
      }
    }
	# orgs is basically just an alias/convenience field based on memberships
    orgs {
      edges {
        node {
          name
        }
      }
    }
  }
}

// ...

builder.objectField(User, 'memberships', (t) =>
  t.loadable({
    type: UserOrgMembersConnection,
    byPath: true,
    args: {
      ...t.arg.connectionArgs(),
    },
    resolve: (member) => member.id,
    load: async (ids: Array<string>, ctx, args) => {
      const orgMembersById = await ctx.findOrgMembersByUserIds(ids)
      return ids.map((id) =>
        resolveArrayConnection({ args }, orgMembersById[id] ?? []),
      )
    },
  }),
)

builder.objectField(User, 'orgs', (t) =>
  t.loadable({
    type: UserOrgsConnection,
    byPath: true,
    args: {
      ...t.arg.connectionArgs(),
    },

    resolve: (user) => user.id,
    load: async (ids: Array<string>, ctx, args) => {
      // Here I'd like to ideally call the dataloader on User.memberships but AFAICT there is no way to get it?
     // e.g. User.memberships.getDataloader(ctx).loadMany(ids)
      const orgMembersById = await ctx.findOrgMembersByUserIds(ids)

      return ids.map((id) =>
        resolveArrayConnection(
          { args },
          orgMembersById[id].map((member) => member.orgId) ?? [],
        ),
      )
    },
  }),
)

Is this possible today and I've just missed it, or is this something unsupported that I need to create an own dataloader for?

[hayes]

Creating your own data-loader for this is the right way to go. I've looked into trying to support this in the data-loader plugin, but couldn't find an API that seemed better than just creating the dataloader directly.

One thing that might be useful is the createContextCache method, that lets you get a dataloader without having to add it to the context object directly. Not really different than what you are already doing, but I like it for encapsulation

const getMemberLoader = createContextCache(() => new DataLoader((ids: readonly string[]) => {
 // Implement dataloader here
}))

builder.objectField(User, 'memberships', (t) =>
  t.loadable({
    type: UserOrgMembersConnection,
    byPath: true,
    args: {
      ...t.arg.connectionArgs(),
    },
    resolve: (member) => member.id,
    load: async (ids: Array<string>, ctx, args) => {
      const orgMembersById = await  getMemberLoader(ctx).loadMany(ids)
      return ids.map((id) =>
        resolveArrayConnection({ args }, orgMembersById[id] ?? []),
      )
    },
  }),
)

[alexandernanberg]

Got it, thanks!