R/updatemerge.R

In basetable: Fast and Memory-Efficient Base R Table Manipulation

updatemerge <- function(x, y, by, cols = NULL) {
  x_dt <- bt_as_data_frame(x)
  y_dt <- bt_as_data_frame(y)
  by <- bt_resolve_cols(x_dt, by)
  bt_resolve_cols(y_dt, by)

  if (is.null(cols)) {
    cols <- setdiff(intersect(names(x_dt), names(y_dt)), by)
  }
  cols <- bt_resolve_cols(x_dt, cols)

  y_first <- bt_as_data_frame(bt_engine_unique(y_dt, by = by, keep_all = TRUE))
  idx <- bt_first_match(x_dt, y_first, by)

  for (nm in cols) {
    values <- y_first[[nm]][idx]
    keep <- !is.na(idx)
    x_dt[[nm]][keep] <- values[keep]
  }

  bt_as_data_table(x_dt)
}