I have a table with two numeric rows, one of which is set to key. I would like to subset my `data.table` by numeric key value, but it doesn't seem to work. When I convert it to character, it works.

Could you help me to understand why is that? I am using data.table 1.8.6.

Thanks a bunch. Here is the test code:

```
> ID <-c(rep(210, 9), rep(3917,6))
> Count <- c(1,1,0,1,1,1,1,1,1,1,1,1,1,0,1)
> x <- data.table(ID, Count)
> 
> # numeric key doesn't work with i argument
> setkey(ID)
 [1]  210  210  210  210  210  210  210  210  210 3917 3917 3917 3917 3917 3917
> x[210,list(ID, Count)]
   ID Count
1: NA    NA
> 
> # create character key
> x$charID <- as.character(x$ID)
> setkey(x, charID)
> x["210",list(ID, Count)]
   charID  ID Count
1:    210 210     1
2:    210 210     1
3:    210 210     0
4:    210 210     1
5:    210 210     1
6:    210 210     1
7:    210 210     1
8:    210 210     1
9:    210 210     1

```