I am trying to figure out a clean way to work with queries and mongdb projections so I don't have to retrieve excessive information from the database.
So assuming I have:
// the query
type Query {
getUserByEmail(email: String!): User
}
And I have a User
with an email
and a username
, to keep things simple. If I send a query and I only want to retrieve the email, I can do the following:
query { getUserByEmail(email: "[email protected]") { email } }
But in the resolver, my DB query still retrieves both username
and email
, but only one of those is passed back by apollo server as the query result.
I only want the DB to retrieve what the query asks for:
// the resolver
getUserByEmail(root, args, context, info) {
// check what fields the query requested
// create a projection to only request those fields
return db.collection('users').findOne({ email: args.email }, { /* projection */ });
}
Of course the problem is, getting information on what the client is requesting isn't so straightforward.
Assuming I pass in request as context - I considered using context.payload
(hapi.js), which has the query string, and searching it through various .split()
s, but that feels kind of dirty. As far as I can tell, info.fieldASTs[0].selectionSet.selections
has the list of fields, and I could check for it's existence in there. I'm not sure how reliable this is. Especially when I start using more complex queries.
Is there a simpler way?
In case you don't use mongDB, a projection is an additional argument you pass in telling it explicitly what to retrieve:
// telling mongoDB to not retrieve _id
db.collection('users').findOne({ email: '[email protected]' }, { _id: 0 })
As always, thanks to the amazing community.
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