R/star_schema_modify_dimension_records.R

In starschemar: Obtaining Stars from Flat Tables

#' Apply dimension record update operations
#'
#' Given a list of dimension record update operations, they are applied on the
#' dimensions of the `star_schema` object. Update operations must be defined
#' with the set of functions available for that purpose.
#'
#' When dimensions are defined, records can be detected that must be modified as
#' part of the data cleaning process: frequently to unify two or more records
#' due to data errors or missing data. This is not immediate because facts must
#' be adapted to the new set of dimension instances.
#'
#' This operation allows us to unify records and automatically propagate
#' modifications to facts.
#'
#' The list of update operations can be applied repeatedly to new data received
#' to be incorporated into the `star_schema` object.
#'
#' @param st A `star_schema` object.
#' @param updates A `record_update_set` object.
#'
#' @return A `star_schema` object.
#'
#' @family data cleaning functions
#'
#' @examples
#'
#' st <- st_mrs_age |>
#'   modify_dimension_records(updates_st_mrs_age)
#'
#' @export
modify_dimension_records <-
  function(st, updates = record_update_set()) {
    UseMethod("modify_dimension_records")
  }


#' @rdname modify_dimension_records
#' @export
modify_dimension_records.star_schema <-
  function(st, updates = record_update_set()) {
    dimensions <- get_all_dimensions(st)
    mod_dim <- update_dimensions(dimensions, updates)
    st <- update_facts_with_dimensions(st, mod_dim)
    st
  }


#' Get all dimensions
#'
#' Get all the dimensions of a star schema.
#'
#' @param st A `star_schema` object.
#'
#' @return A list of `dimension_table` objects.
#' @keywords internal
get_all_dimensions <- function(st) {
  names <- get_dimension_names(st)
  dimensions <- st$dimension[names]
  for (n in names) {
    dimensions[[n]] <- get_dimension(st, n)
  }
  dimensions
}