shortcut prefix x. and i. for variables in joins in 1.9.3

[arunsrinivasan]

In 1.9.3, there should be ways to access x's key columns in j directly (and i's key columns as well) using the shortcut prefix x. and i..

dta <- data.table(idx=1:3, vala=4:6, key="idx")
dtb <- data.table(idx=c(1,4), valb=c(10,11), key="idx")

# (1)
dta[dtb, list(idx, sum(valb)), by=.EACHI]
#   idx idx V2
#1:   1   1 10
#2:   4  NA 11

# (2)
dta[dtb, list(x.idx, sum(valb)), by=.EACHI]
# Error in `[.data.table`(dta, dtb, list(x.idx, sum(valb)), by = .EACHI) : 
#   object 'x.idx' not found

(2) should return:

# x.idx V2
#     1 10
#    NA 11

PS: Note that there's already a related issue #471 on (1) regarding names of data.table join in 1.9.3.

[jangorecki]

This was resolved by @arunsrinivasan in 620276b

[jangorecki]

not yet works with .EACHI