How to add two strings as numbers together in mongoDB

Question

my guestMin and guestMax are both strings, and I want to add them together and put the sum into guestSum.

I tried this:

$project:{
    "_id" : 1,                                 
    "name" : 1,
    "guestsMin" : 1,
    "guestsMax" : 1,
    "guestSum" : parseInt("guestsMin") + parseInt("guestsMax"),
    "gmapsdata" : 1
}

this does not show the guestSum at all

$project:{
    "_id" : 1,                                 
    "name" : 1,
    "guestsMin" : 1,
    "guestsMax" : 1,
    "guestSum" : { $add: [ parseInt("guestsMin"), parseInt("guestsMax") ] },
    "gmapsdata" : 1
}

this gives "guestSum": null,

    "guestSum" : { $add: [ parseInt("$guestsMin"), parseInt("$guestsMax") ] },

this gives "guestSum": null,

    "guestSum" : { $multiply: [ parseInt("$guestsMin"), parseInt("$guestsMax") ] },

this gives "guestSum": null,

    "guestSum" : { $multiply: [ parseInt("property.guestsMin"), parseInt("property.guestsMax") ] },

this gives "guestSum": null,

Im running out of ideas, anyone?

seems like you cannot convert the string to the number in aggregation pipeline https://stackoverflow.com/questions/25983228/convert-a-string-to-a-number-in-mongodb-projection — Sergey Berezovskiy, Jul 05 '17 at 12:43
@Sergey hmmm perhaps you are right - but when I remove the parseInt, then it complains about multiplying strings. So it looks like the parseInt part is working fine. Just crap that I have to do a loop in js to add these two numbers together. — torbenrudgaard, Jul 05 '17 at 13:11
The right thing to do here is fix all the docs so that these fields use numeric values. Otherwise you'll be fighting this forever. — JohnnyHK, Jul 05 '17 at 13:40
@JohnnyHK hehe exactly!! So I did - last night I converted all the guestMin and guestMax to be numeric. And that made things a lot more easy — torbenrudgaard, Jul 06 '17 at 06:41

score 0 · Answer 1 · answered Jul 05 '17 at 15:30

0

The solution was this:

"guestSort" : { $multiply: [ "$guestsMin", "$guestsMax"] },

"property.guestsMin" did not work

"guestsMin" did not work

"$property.guestsMin" did not work

but... "$guestsMin" worked

answered Jul 05 '17 at 15:30

torbenrudgaard

2,375
7
32
53

How to add two strings as numbers together in mongoDB

1 Answers1