djnavarro commented on a change in pull request #12154:
URL: https://github.com/apache/arrow/pull/12154#discussion_r785525181
##########
File path: r/R/util.R
##########
@@ -209,3 +209,74 @@ handle_csv_read_error <- function(e, schema) {
abort(e)
}
+
+
+parse_period_unit <- function(x) {
+
+ # the regexp matches against fractional units, but per lubridate
+ # supports integer multiples of a known unit only
+ match_info <- regexpr(
+ pattern = " *(?<multiple>[0-9.,]+)? *(?<unit>[^ \t\n]+)",
+ text = x[[1]],
+ perl = TRUE
+ )
+
+ capture_start <- attr(match_info, "capture.start")
+ capture_length <- attr(match_info, "capture.length")
+ capture_end <- capture_start + capture_length - 1L
+
+ str_unit <- substr(x, capture_start[[2]], capture_end[[2]])
+ str_multiple <- substr(x, capture_start[[1]], capture_end[[1]])
+
+ known_units <- c("nanosecond", "microsecond", "millisecond", "second",
+ "minute", "hour", "day", "week", "month", "quarter", "year")
+
+ # match the period unit
+ str_unit_start <- substr(str_unit, 1, 3)
+ unit <- as.integer(pmatch(str_unit_start, known_units)) - 1L
+
+ if(any(is.na(unit))) {
+ abort(sprintf("Unknown unit '%s'", str_unit))
+ }
+
+ # empty string in multiple interpreted as 1
+ if(capture_length[[1]] == 0) {
+ multiple <- 1L
+
+ } else {
+
+ # special cases: interpret fractions of 1 second as integer
+ # multiples of nanoseconds, microseconds, or milliseconds
+ # to mirror lubridate syntax
+ multiple <- as.numeric(str_multiple)
+
+ if(unit == 3L & multiple < 10^-6) {
+ unit <- 0L
+ multiple <- 10^9 * multiple
+ }
+ if(unit == 3L & multiple < 10^-3) {
+ unit <- 1L
+ multiple <- 10^6 * multiple
+ }
+ if(unit == 3L & multiple < 1) {
+ unit <- 2L
+ multiple <- 10^3 * multiple
+ }
+
+ multiple <- as.integer(multiple)
+ }
+
+ # more special cases: lubridate imposes sensible maximum
+ # values on the number of seconds, minutes and hours
+ if(unit == 3L & multiple > 60) {
+ abort("Rounding with second > 60 is not supported")
+ }
Review comment:
That's a really good point. Maybe erring on the side of caution and
mirroring lubridate as closely as possible would be best? It's going to come up
again as an issue once I try to sort out the issue associated with the
`change_on_boundary` argument, actually
--
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
