Github user sun-rui commented on the pull request:
https://github.com/apache/spark/pull/12836#issuecomment-220974249
@NarineK, @shivaram, @davies, the pending issue is the signature of the R
function. I think there are 3 options:
1. function(df), where df is the data.frame of the group, containing the
grouping columns. If the R function needs to use the key, it has to extract it
from df itself.
2. function(key, df), where key is a list of grouping column values for
this group, df is the data.frame of the group, containing the grouping columns.
This is similar to the scala function signature for
KeyValueGroupedData.flatMapGroups().
3. function(key, df), where where key is a list of grouping column values
for this group, df is the data.frame of the group, NOT containing the grouping
columns. This has the benefit of saving communication traffic
I personally like option 2. But technically it is possible to support both
1&2 or 1&3.
let's vote for a decision.
@NarineK, Could you please investigate if there is any existing convention
in R packages for such usage?
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