Github user davies commented on a diff in the pull request:
https://github.com/apache/spark/pull/12493#discussion_r60446033
--- Diff: R/pkg/R/generics.R ---
@@ -439,6 +439,10 @@ setGeneric("covar_samp", function(col1, col2)
{standardGeneric("covar_samp") })
#' @export
setGeneric("covar_pop", function(col1, col2) {standardGeneric("covar_pop")
})
+#' @rdname dapply
+#' @export
+setGeneric("dapply", function(x, func, schema = NULL) {
standardGeneric("dapply") })
--- End diff --
The two use cases could be done by:
1) combine multiple directly chained functions into single one, this is
also useful even we support the no-schema mapPartition()
2) The serializer in JVM should be much faster than that in R. In order to
speedup collect for R, maybe another column format (column in R) could be
faster than current (rows in R and Java). This could be another topic.
Once we expose the raw format to users, user may see it as public
interface, may save the binary as parquet file, it's hard to maintain it in
compatible way.
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