dplyr-group-by.R

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# to you under the Apache License, Version 2.0 (the
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# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
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# software distributed under the License is distributed on an
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# specific language governing permissions and limitations
# under the License.


# The following S3 methods are registered on load if dplyr is present

group_by.arrow_dplyr_query <- function(.data,
                                       ...,
                                       .add = FALSE,
                                       add = NULL,
                                       .drop = dplyr::group_by_drop_default(.data)) {
  if (!missing(add)) {
    .Deprecated(
      msg = paste(
        "The `add` argument of `group_by()` is deprecated.",
        "Please use the `.add` argument instead."
      )
    )
    .add <- add
  }

  .data <- as_adq(.data)
  expression_list <- expand_across(.data, quos(...))
  new_groups <- ensure_named_exprs(expression_list)

  # set up group names and check which are new
  gbp <- dplyr::group_by_prepare(.data, !!!expression_list, .add = .add)
  existing_groups <- dplyr::group_vars(gbp$data)
  new_group_names <- setdiff(gbp$group_names, existing_groups)

  names(new_groups) <- new_group_names

  if (length(new_groups)) {
    # Add them to the data
    .data <- dplyr::mutate(.data, !!!new_groups)
  }

  .data$group_by_vars <- gbp$group_names
  .data$drop_empty_groups <- ifelse(length(gbp$group_names), .drop, dplyr::group_by_drop_default(.data))
  .data
}
group_by.Dataset <- group_by.ArrowTabular <- group_by.RecordBatchReader <- group_by.arrow_dplyr_query

groups.arrow_dplyr_query <- function(x) syms(dplyr::group_vars(x))
groups.Dataset <- groups.ArrowTabular <- groups.RecordBatchReader <- groups.arrow_dplyr_query

group_vars.arrow_dplyr_query <- function(x) x$group_by_vars
group_vars.Dataset <- function(x) character()
group_vars.RecordBatchReader <- function(x) character()
group_vars.ArrowTabular <- function(x) {
  x$metadata$r$attributes$.group_vars %||% character()
}

# the logical literal in the two functions below controls the default value of
# the .drop argument to group_by()
group_by_drop_default.arrow_dplyr_query <- function(.tbl) {
  .tbl$drop_empty_groups %||% TRUE
}
group_by_drop_default.ArrowTabular <- function(.tbl) {
  .tbl$metadata$r$attributes$.group_by_drop %||% TRUE
}
group_by_drop_default.Dataset <- group_by_drop_default.RecordBatchReader <-
  function(.tbl) TRUE

ungroup.arrow_dplyr_query <- function(x, ...) {
  x$group_by_vars <- character()
  x$drop_empty_groups <- NULL
  x
}
ungroup.Dataset <- ungroup.RecordBatchReader <- force
ungroup.ArrowTabular <- function(x) {
  set_group_attributes(x, NULL, NULL)
}

# Function to call after evaluating a query (as_arrow_table()) to add back any
# group attributes to the Schema metadata. Or to remove them, pass NULL.
set_group_attributes <- function(tab, group_vars, .drop) {
  # dplyr::group_vars() returns character(0)
  # so passing NULL means unset (ungroup)
  if (is.null(group_vars) || length(group_vars)) {
    # Since accessing schema metadata does some work, only overwrite if needed
    new_atts <- old_atts <- tab$metadata$r$attributes %||% list()
    new_atts[[".group_vars"]] <- group_vars
    new_atts[[".group_by_drop"]] <- .drop
    if (!identical(new_atts, old_atts)) {
      tab$metadata$r$attributes <- new_atts
    }
  }
  tab
}