# upcToID.r

upcToID_ <- function(DT, factor=TRUE, showWarnings=TRUE) {
  key.bak <- key(DT)
  if ("upc" %ni% names(DT)) {
      if (showWarnings) warning ("DT does not have a column named 'upc'", call.=TRUE)
  } else if (factor) {
      DT[, upc := as.idcolfactor(upc)]
  } else {
      DT[, upc := as.idcol(upc)]
  }

  setkeyIfNot(DT, key.bak, verbose=FALSE)
  return(invisible(DT))
}