register_binding: Register compute bindings

In arrow: Integration to 'Apache' 'Arrow'

Register compute bindings

Description

register_binding() is used to populate a list of functions that operate on (and return) Expressions. These are the basis for the .data mask inside dplyr methods.

Usage

register_binding(fun_name, fun, notes = character(0))

Arguments

fun_name	A string containing a function name in the form "function" or "package::function".
fun	A function, or NULL to un-register a previous function. This function must accept Expression objects as arguments and return Expression objects instead of regular R objects.
notes	string for the docs: note any limitations or differences in behavior between the Arrow version and the R function.

Value

The previously registered binding or NULL if no previously registered function existed.

Writing bindings

• Expression$create() will wrap any non-Expression inputs as Scalar Expressions. If you want to try to coerce scalar inputs to match the type of the Expression(s) in the arguments, call cast_scalars_to_common_type(args) on the args. For example, Expression$create("add", args = list(int16_field, 1)) would result in a float64 type output because 1 is a double in R. To prevent casting all of the data in int16_field to float and to preserve it as int16, do Expression$create("add", args = cast_scalars_to_common_type(list(int16_field, 1)))

• Inside your function, you can call any other binding with call_binding().

arrow documentation built on Sept. 11, 2024, 8:02 p.m.