jorisvandenbossche commented on code in PR #13397:
URL: https://github.com/apache/arrow/pull/13397#discussion_r916603841
##########
r/R/compute.R:
##########
@@ -307,3 +307,158 @@ cast_options <- function(safe = TRUE, ...) {
)
modifyList(opts, list(...))
}
+
+#' Register user-defined functions
+#'
+#' These functions support calling R code from query engine execution
+#' (i.e., a [dplyr::mutate()] or [dplyr::filter()] on a [Table] or [Dataset]).
+#' Use [arrow_scalar_function()] to define an R function that accepts and
+#' returns R objects; use [arrow_base_scalar_function()] to define a
+#' lower-level function that operates directly on Arrow objects.
+#'
+#' @param name The function name to be used in the dplyr bindings
+#' @param scalar_function An object created with [arrow_scalar_function()]
+#' or [arrow_base_scalar_function()].
+#' @param registry_name The function name to be used in the Arrow C++
+#' compute function registry. This may be different from `name`.
+#' @param in_type A [DataType] of the input type or a [schema()]
+#' for functions with more than one argument. This signature will be used
+#' to determine if this function is appropriate for a given set of arguments.
+#' If this function is appropriate for more than one signature, pass a
+#' `list()` of the above.
+#' @param out_type A [DataType] of the output type or a function accepting
+#' a single argument (`types`), which is a `list()` of [DataType]s. If a
+#' function it must return a [DataType].
+#' @param fun An R function or rlang-style lambda expression. This function
+#' will be called with R objects as arguments and must return an object
+#' that can be converted to an [Array] using [as_arrow_array()]. Function
+#' authors must take care to return an array castable to the output data
+#' type specified by `out_type`.
+#' @param base_fun An R function or rlang-style lambda expression. This
+#' function will be called with exactly two arguments: `kernel_context`,
+#' which is a `list()` of objects giving information about the
+#' execution context and `args`, which is a list of [Array] or [Scalar]
+#' objects corresponding to the input arguments.
+#'
+#' @return
+#' - `register_scalar_function()`: `NULL`, invisibly
+#' - `arrow_scalar_function()`: returns an object of class
+#' "arrow_base_scalar_function" that can be passed to
+#' `register_scalar_function()`.
+#' @export
+#'
+#' @examplesIf .Machine$sizeof.pointer >= 8
+#' fun_wrapper <- arrow_scalar_function(
+#' schema(x = float64(), y = float64(), z = float64()),
+#' float64(),
+#' function(x, y, z) x + y + z
+#' )
+#' register_scalar_function("example_add3", fun_wrapper)
+#'
+#' call_function(
+#' "example_add3",
+#' Scalar$create(1),
+#' Scalar$create(2),
+#' Array$create(3)
+#' )
+#'
+#' # use arrow_base_scalar_function() for a lower-level interface
+#' base_fun_wrapper <- arrow_base_scalar_function(
+#' schema(x = float64(), y = float64(), z = float64()),
+#' float64(),
+#' function(context, args) {
+#' args[[1]] + args[[2]] + args[[3]]
+#' }
+#' )
+#' register_scalar_function("example_add3", base_fun_wrapper)
+#'
+#' call_function(
+#' "example_add3",
+#' Scalar$create(1),
+#' Scalar$create(2),
+#' Array$create(3)
+#' )
+#'
+register_scalar_function <- function(name, scalar_function, registry_name =
name) {
Review Comment:
For reference, I _think_ the reason that in pyarrow we decided to use
"scalar" in the name of the register function, is that in the future we also
want to allow other types of UDFs, and for example a vector function could have
the same signature than a scalar function (in terms of input / output data
types), so I am not sure you can guess the kernel type based on the arguments.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: github-unsubscr...@arrow.apache.org
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
