Change proposal for over 20x speedup in findManyByIds

[gamebak]

Speed up proposal for method findManyByIds.

apollo-datasource-mongodb/src/cache.js

Line 173 in 08e1c07

return Promise.all(ids.map(id => methods.findOneById(id, { ttl })))

As-Is right now, it's opening a lot of findOneById with a promise.all, but it's really inefficient once you have over 100 keys and it's slowing the UI.

While I don't exactly know how to implement this in the library exactly, the solution will look similar to this at the mongo level:

 this.collection.find({ _id: { $in: arrIds } })

This will result in a single call to the server-side, speeding up for bigger queries.

[0xChqrles]

@gamebak In the end Dataloader only makes a single request with all the ids passed

[gamebak]

It doesn't, I've tested this, unless I'm missing something.

[lorensr]

It's certainly the intent of the DataLoader function to use $in:

apollo-datasource-mongodb/src/cache.js

Line 112 in 2e048ce

if (!filter[fieldName]) filter[fieldName] = { $in: [] }

If it's not working, would be happy to look at a PR that fixes it.