问题
I try to do some integer math in mongodb and have some problems. Is there a way to round doubles up or down in the mongo db aggregation framework?
回答1:
As per the comment from Stennie, the floor and ceiling methods are not supported.
And as per my comment above, the best solution that I could find was just doing an operation that looks like: (num-mod(num,1)) which should yield the same result as the floor function.
回答2:
Starting from MongoDB 3.2, you can use the following arithmetic aggregation operators are available:
- ceil
- trunc
- floor
which allow to convert to integer from any side you want. The syntax is straight-forward: { $function: <number> }
来源：https://stackoverflow.com/questions/13617526/is-there-a-floor-function-in-mongodb-aggregation-framework