Repository navigation
"Can't assign to the same column twice in the same query" message unhelpful, and inconsistent #2967
Description
DT = data.table(a = 1:5)
DT[ , c('b', 'b') := 10]
# Error in `[.data.table`(DT, , `:=`(c("b", "b"), 10)) :
# Can't assign to the same column twice in the same query (duplicates detected).
In more dynamic situations, this error is rather unhelpful.
Error happens here at the C level:
if (any_duplicated(cols,FALSE)) error("Can't assign to the same column twice in the same query (duplicates detected).");
any_duplicated is part of the R C API, the second argument is from_last.
Probably OK to jump to using something with Duplicated within the if (any_duplicated(cols, FALSE)) branch.
What's more, this error doesn't occur if the assignment takes place with by:
DT[ , c('b', 'b') := 10, by = a]
# a b
# 1: 1 10
# 2: 2 10
# 3: 3 10
# 4: 4 10
# 5: 5 10
Activity
[-]"Can't assign to the same column twice in the same query" message unhelpful[/-][+]"Can't assign to the same column twice in the same query" message unhelpful, and inconsistent[/+]