djnavarro commented on code in PR #12154:
URL: https://github.com/apache/arrow/pull/12154#discussion_r926134717
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r/R/util.R:
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@@ -215,3 +215,138 @@ handle_csv_read_error <- function(e, schema, call) {
is_compressed <- function(compression) {
!identical(compression, "uncompressed")
}
+
+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
Review Comment:
Yeah, this is bothering me too. Personally I would prefer to be stricter to
avoid the `"3 mickeys"` problem, but if I were to do that it would break
compatibility with lubridate. The substring matching I've implemented here is
an exact mirror of how lubridate handles it (I think). In this instance I felt
that lubridate compatibility was the more important consideration, because
someone might be relying on it, e.g., by using something like `"3 microsecs"`
or some other abbreviation that I can't predict. Unless you feel strongly I'd
prefer to leave it as is, and add a comment explaining the logic for this
design choice so that we remember why we did it this way
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