R/dbGetInfo.R

In RPresto: DBI Connector to Presto

# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
#
# This source code is licensed under the BSD-style license found in the
# LICENSE file in the root directory of this source tree.

#' @include PrestoDriver.R PrestoConnection.R PrestoResult.R
NULL

#' Metadata about database objects
#' @rdname dbGetInfo
#' @importMethodsFrom DBI dbGetInfo
#' @export
setMethod(
  "dbGetInfo",
  "PrestoDriver",
  function(dbObj) {
    return()
  }
)

#' @rdname dbGetInfo
#' @importMethodsFrom DBI dbGetInfo
#' @export
setMethod(
  "dbGetInfo",
  "PrestoConnection",
  function(dbObj) {
    return(list(
      host = dbObj@host,
      port = dbObj@port,
      user = dbObj@user,
      catalog = dbObj@catalog,
      schema = dbObj@schema
    ))
  }
)

.dbGetInfo.PrestoResult <- function(dbObj) {
  return(list(
    query.id = dbObj@query$id(),
    statement = .dbGetStatement(dbObj),
    row.count = .dbGetRowCount(dbObj),
    has.completed = .dbHasCompleted(dbObj),
    stats = dbObj@query$stats()
  ))
}


#' For the [PrestoResult-class] object, the implementation
#' returns the additional `stats` field which can be used to
#' implement things like progress bars. See the examples section.
#' @param dbObj A [PrestoDriver-class],
#'          [PrestoConnection-class]
#'          or [PrestoResult-class] object
#' @return [PrestoResult-class] A [list()] with elements
#'   \describe{
#'     \item{statement}{The SQL sent to the database}
#'     \item{row.count}{Number of rows fetched so far}
#'     \item{has.completed}{Whether all data has been fetched}
#'     \item{stats}{Current stats on the query}
#'   }
#' @rdname dbGetInfo
#' @importMethodsFrom DBI dbGetInfo
#' @export
#' @examples
#' \dontrun{
#' conn <- dbConnect(Presto(), "localhost", 7777, "onur", "datascience")
#' result <- dbSendQuery(conn, "SELECT * FROM jonchang_iris")
#' iris <- data.frame()
#' progress.bar <- NULL
#' while (!dbHasCompleted(result)) {
#'   chunk <- dbFetch(result)
#'   if (!NROW(iris)) {
#'     iris <- chunk
#'   } else if (NROW(chunk)) {
#'     iris <- rbind(iris, chunk)
#'   }
#'   stats <- dbGetInfo(result)[["stats"]]
#'   if (is.null(progress.bar)) {
#'     progress.bar <- txtProgressBar(0, stats[["totalSplits"]], style = 3)
#'   } else {
#'     setTxtProgressBar(progress.bar, stats[["completedSplits"]])
#'   }
#' }
#' close(progress.bar)
#' }
setMethod("dbGetInfo", "PrestoResult", .dbGetInfo.PrestoResult)