R/sqlQuery.cached.R

In erikjandevries/r.dstools.ej: Data Science Tools by Erik Jan

#' @title
#' Query an ODBC Database (Cached)
#'
#' @description
#' Wrapper functions to implement caching for the \code{\link{sqlQuery}} function using RDS-files.
#'
#' @param rds The name of the file in which the cache is to be stored.
#' @param channel Connection handle as returned by \code{\link{odbcConnect}}.
#' @param query Any valid SQL statement.
#' @param ... Additional arguments to be passed to \code{\link{sqlQuery}}.
#'
#' @details
#' If the \code{rds} file exists, the object will be loaded from the \code{rds}.
#' Otherwise the \code{query} will be sent to the ODBC database via the\
#' \code{channel}, and an \code{rds} of the returned object will be saved.
#'
#' @seealso
#' \code{\link{do.call.cached}} which is the wrapper function that performs the caching.
#'
#' \code{\link{sqlQuery}} which is called to submit the \code{query} to an ODBC database, and retrieve the results.
#'
#' @examples
#' sqlQuery.cached(dbHandle, "SELECT COUNT(*) FROM CUSTOMERS")
#'
#' @export
sqlQuery.cached <- function(rds, channel, query, ...) {
  obj <- do.call.cached(rds, RODBC::sqlQuery, c(channel, query, list(...)));
  return(obj);
}