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#' Return the column names of the disk.frame
#'
#' The returned column names are from the source. So if you have lazy operations
#' then the \code{colnames} here does not reflects the results of those
#' operations. Note: if you have expensive lazy function then this operation
#' might take some time.
#'
#' @param x a disk.frame
#' @param ... not used
#' @export
#' @importFrom fs dir_ls
#' @importFrom fst metadata_fst
#' @export
colnames <- function(x, ...) {
UseMethod("colnames")
}
#' @rdname colnames
#' @export
names.disk.frame <- function(x, ...) {
colnames.disk.frame(x, ...)
}
#' @rdname colnames
#' @export
colnames.disk.frame <- function(x, ...) {
res = attr(x, "path", exact=TRUE) %>%
list.files(full.names = TRUE, recursive=TRUE, pattern = "fst")
# if(is.null(attr(x, "recordings"))) {
if(length(res) == 0) {
return(vector("character"))
}
return(fst::metadata_fst(res[1])$columnNames)
# } else {
# tiny_example_data.frame = get_chunk(x, 1, from=1, to=1)
# return(colnames(tiny_example_data.frame))
# }
}
#' @rdname colnames
#' @export
colnames.default <- function(x, ...) {
base::colnames(x, ...)
}
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