Auto increment for Postgres (for use within a package)

pq_auto_increment.R

#' @importFrom methods setOldClass setMethod
#' @importMethodsFrom DBI dbDataType
#' @importClassesFrom RPostgres PqConnection

#' Generate SQL for custom data types
#'
#' SQL for data types as described in [auto_increment()] can be generated
#' using [DBI::dbDataType()].
#'
#' @param dbObj Object for determining SQL dialect (e.g. connection)
#' @param obj Object for determining SQL type
#' @param ... Generic consistency
#'
#' @name dbDataType
#' @aliases dbDataType,PqConnection,data.frame-method
#' @rdname custom-dbDataType
#' @export
setMethod(
  "dbDataType",
  signature("PqConnection", "data.frame"),
  function(dbObj, obj, ...) {
    res <- Map(
      function(x, i) {
        dbDataType(dbObj, x, col = DBI::dbQuoteIdentifier(dbObj, i))
      },
      obj,
      names(obj)
    )
    stopifnot(all(lgl_ply(res, is_string)))
    unlist(res)
  }
)

setOldClass("auto_increment")

#' Auto increment type
#'
#' Class constructor for support of an auto increment type.
#'
#' @param size Integer size
#'
#' @export
auto_increment <- function(size = c(NA, "small", "big")) {
  structure(integer(), size = match.arg(size), class = "auto_increment")
}

#' @name dbDataType
#' @aliases dbDataType,PqConnection,auto_increment-method
#' @rdname custom-dbDataType
#' @export
setMethod(
  "dbDataType",
  signature("PqConnection", "auto_increment"),
  function(dbObj, obj, ...) {
    size <- attr(obj, "size")
    if (is.na(size)) size <- ""
    paste0(size, "serial")
  }
)