dragosmg commented on a change in pull request #12506:
URL: https://github.com/apache/arrow/pull/12506#discussion_r831914535
##########
File path: r/R/dplyr-funcs-datetime.R
##########
@@ -233,6 +236,68 @@ register_bindings_datetime <- function() {
tz = "UTC") {
call_binding("make_datetime", year, month, day, hour, min, sec, tz)
})
+ register_binding("difftime", function(time1,
+ time2,
+ tz,
+ units = "secs") {
+ if (units != "secs") {
+ abort("`difftime()` with units other than `secs` not supported in Arrow")
+ }
+
+ if (!missing(tz)) {
+ warn("`tz` argument is not supported in Arrow, so it will be ignored")
+ }
+
+ # cast to timestamp if time1 and time2 are not dates or timpestamp
expressions
+ # (the subtraction of which would output a `duration`)
+ if (!(inherits(time1, "Expression") &&
+ time1$type_id() %in% Type[c("TIMESTAMP", "DATE32", "DATE64")])) {
+ time1 <- build_expr("cast", time1, options = cast_options(to_type =
timestamp(timezone = "UTC")))
+ }
+
+ if (!(inherits(time2, "Expression") &&
+ time2$type_id() %in% Type[c("TIMESTAMP", "DATE32", "DATE64")])) {
+ time2 <- build_expr("cast", time2, options = cast_options(to_type =
timestamp(timezone = "UTC")))
+ }
Review comment:
This is the final line in that binding (row 264):
```r
build_expr("cast", time1 - time2, options = cast_options(to_type =
duration("s")))
```
if we use `!call_binging("is.instant", time1)` it means that when `time1` is
a POSIXct object it will bypass the cast to timestamp and jump straight to
building the subtraction -> casting expression. We get an error because of the
subtraction operation `-`.
```r
via_table <- rlang::eval_tidy(expr, rlang::new_data_mask(rlang::env(.input =
arrow_table(tbl))))` threw an unexpected warning.
Message: Incompatible methods ("-.POSIXt", "Ops.Expression") for "-"
Class: simpleWarning/warning/condition
```
I guess we could build a subtraction expression, but that feels more
complicated to me - too big a trade-off for using `is.instant`.
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