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[R-Forge #2296] Copy-on-:= at column level, DT[,list(...)] shallow copy and add cols to shallow(DT, cols) #617
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@mattdowle, the idea we recently discussed is already here (and written here in an even better fashion). Would be great to have this for next release! Also in my wish list for
shallow()to accept a set of columns.. We could'veshallow()andshallowv()like usual.- added a commit that references this issue
on Nov 1, 2014 - removed this from the milestone
on May 10, 2018
Submitted by: Matt Dowle; Assigned to: Nobody; R-Forge link
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shallow().would add reference counter attribute. (Both
DT2[1,a:=5L]ANDDT[1,a:=5L]would need to copy a. Maybe the ExternalPointer destructor could decrement as well, so arm(DT2)would automatically takeDTback to being the sole copy.Then with this in place,
could do shallow copies, too. See TO DO in source.
In the meantime, allow
shallow()to accept a subset of columns and then use it induplicated.Rto save the copies of the by columns there. Upped priority for this part (easier).