[datatable-help] new key argument to [.data.table in 1.8.11

[Frank Erickson]

>
> There wasn't a 'key' argument before and yes, it will change the key
> regardless of whether you're merging or not. Initially I added it just for
> the merges, but then realized that there us no conceptual reason to
> restrict it just to merges.


Ah, my mistake. I saw "key" under the list of arguments in the
documentation and assumed it applied to [.data.table; but it's actually for
the data.table function.

Ah what am I thinking - you'll have to copy and still set a key, so unless
> you have to go back to the old key (rarely?) this is strictly faster.
>

Yeah, that was my initial use case, a "temporary key". This new
syntax/functionality should be useful when I don't want to go back to the
old key, though.

--Frank

>
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