dragosmg commented on code in PR #13196:
URL: https://github.com/apache/arrow/pull/13196#discussion_r905009285
##########
r/R/dplyr-datetime-helpers.R:
##########
@@ -200,20 +236,193 @@ build_formats <- function(orders) {
unique(formats)
}
+#' Build formats from a single order
+#'
+#' @param order a single string date-time format, such as `"ymd"` or
`"ymd_hms"`
+#'
+#' @return a vector of all possible formats derived from the input
+#' order
+#'
+#' @noRd
build_format_from_order <- function(order) {
- year_chars <- c("%y", "%Y")
- month_chars <- c("%m", "%B", "%b")
- day_chars <- "%d"
-
- outcome <- switch(
- order,
- "ymd" = expand.grid(year_chars, month_chars, day_chars),
- "ydm" = expand.grid(year_chars, day_chars, month_chars),
- "mdy" = expand.grid(month_chars, day_chars, year_chars),
- "myd" = expand.grid(month_chars, year_chars, day_chars),
- "dmy" = expand.grid(day_chars, month_chars, year_chars),
- "dym" = expand.grid(day_chars, year_chars, month_chars)
+ char_list <- list(
+ "y" = c("%y", "%Y"),
+ "m" = c("%m", "%B", "%b"),
+ "d" = "%d",
+ "H" = "%H",
+ "M" = "%M",
+ "S" = "%S",
+ "I" = "%I"
+ )
+
+ split_order <- strsplit(order, split = "")[[1]]
+
+ outcome <- expand.grid(char_list[split_order])
+ # we combine formats with and without the "-" separator, we will later
+ # coalesce through all of them (benchmarking indicated this is a more
+ # computationally efficient approach rather than figuring out if a string has
+ # separators or not and applying only )
+ # during parsing if the string to be parsed does not contain a separator
+ formats_with_sep <- do.call(paste, c(outcome, sep = "-"))
+ formats_without_sep <- do.call(paste, c(outcome, sep = ""))
+ c(formats_with_sep, formats_without_sep)
+}
+
+#' Process data in preparation for parsing
+#'
+#' `process_data_for_parsing()` takes a data column and a vector of `orders`
and
+#' prepares several versions of the input data:
+#' * `processed_x` is a version of `x` where all separators were replaced
with
+#' `"-"` and multiple separators were collapsed into a single one. This
element
+#' is only set to an empty list when the `orders` argument indicate we're only
+#' interested in parsing the augmented version of `x`.
+#' * each of the other 3 elements augment `x` in some way
+#' * `augmented_x_ym` - builds the `ym` and `my` formats by adding `"01"`
+#' (to indicate the first day of the month)
+#' * `augmented_x_yq` - transforms the `yq` format to `ymd`, by deriving the
+#' first month of the quarter and adding `"01"` to indicate the first day
+#' * `augmented_x_qy` - transforms the `qy` format to `ymd` in a similar
+#' manner to `"yq"`
+#'
+#' @param x an Expression corresponding to a character or numeric vector of
+#' dates to be parsed.
+#' @param orders a character vector of date-time formats.
+#'
+#' @return a list made up of 4 lists, each a different version of x:
+#' * `processed_x`
+#' * `augmented_x_ym`
+#' * `augmented_x_yq`
+#' * `augmented_x_qy`
+#' @noRd
+process_data_for_parsing <- function(x,
+ orders) {
Review Comment:
Done
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