how do i add a value to the top of an array in mongodb?

Question

how do i add a value to the top of an array in mongodb?

say i have this document in my mongo collection:

{ \"colors\" : [ \"red\", \"green\", \"blue\         


        

Answer 1

"unshift" inserts data in the front of an array.. whereas "push" inserts it at the end. e.g. in JavaScript:

> a = ['red','green','blue']
[ "red", "green", "blue" ]
> a.unshift("yellow")
4
> a
[ "yellow", "red", "green", "blue" ]

But unfortunately this isn't supported by the Mongo API as an atomic operation:

http://www.mongodb.org/display/DOCS/Updating

it just supports "push"

---

How big is your array?

you could ether assume that your array in Mongo is always stored in reverse, and use push, or you could read-out the array, modify it with unshift, and then store it again (which wouldn't be atomic though)