Mongoose: Score query then sort by score - non text fields - mongodb

Question

In my db, I have a collection of books.
Each have:
a count of upvotes
a count of downvotes
a count of views
I would like to sort my db by scoring as follows:
upvote: 8 points
downvote: -4 points
view: 1/2 point
So the score will be:
(NumberOfViews*(1/2)) + (NumberOfDownvotes*-4)+ (NumberOfUpvotes*8)
So if I have:
book1 = {name:'book1', views:3000,upvotes:340, downvotes:120}
book2 = {name:'book2', views:9000,upvotes:210, downvotes:620}
book3 = {name:'book3', views:7000,upvotes:6010, downvotes:2}
The score should be:
book1Score = 3740
book2Score = 3700
book3Score = 51572
And the query should output
book3,book1,book2
How can I achieve such a thing in mongoose?
Bonus: What if I want records that are more recent to rank higher than older records on that same query?
Thanks

Answer 1

Well I ended up doing it all inside mongoose.
I run this query every 24 hours to re-score my collection.
Book.aggregate(
[
//I match my query
{$match:query},
{
$project: {
//take the id for reference
_id: 1,
//calculate the score of the views
viewScore: {
$multiply: [ "$views", 0.5 ]
},
//calculate the score of the upvotes
upvoteScore: {
$multiply: [ {$size: '$upvotes'}, 8 ]
},
//calculate the score of the downvotes
downvoteScore: {
$multiply: [ {$size: '$downvotes'}, -4 ]
}
}
},
{
//project a second time
$project: {
//take my id for reference
_id: 1,
//get my total score
score: {
$add:['$viewScore','$upvoteScore','$downvoteScore']
},
}
},
//sort by the score.
{$sort : {'score' : -1}},
]
)

Answer 2

I think the best way would be to query mongoose for the list of book then do the sorting yourself.
Something like:
// Get query results from mongoose then ...
books.sort((a,b) => {
return ((a.views*(1/2))+(a.downvotes*-4)+(a.upvotes*8))-((b.view*(1/2))+ b.downvotes*-4)+(b.upvotes*8))
});
This would sort the books in ascending order of highest points
EDIT: The above answer is for sorting after you've received the query. (And also just realized you want descending for above^ so just switch the placement to be b - a)
If you want to receive the query already sorted, you could instead calculate the score at the time you input the book and add that as a field. The use mongoose's Query#sort. Which would look something like
query.sort({ score: 'desc'});
More info on Query#sort: http://mongoosejs.com/docs/api.html#query_Query-sort