R/register.R

In duckdb: DBI Package for the DuckDB Database Management System

# helper to clean up non-utf and posixlt vectors
encode_values <- function(value) {
  if (!is.null(names(value))) {
    names(value) <- enc2utf8(names(value))
  }

  is_character <- vapply(value, is.character, logical(1))
  value[is_character] <- lapply(value[is_character], enc2utf8)
  is_factor <- vapply(value, is.factor, logical(1))
  value[is_factor] <- lapply(value[is_factor], function(x) {
    levels(x) <- enc2utf8(levels(x))
    x
  })

  is_posixlt <- vapply(value, inherits, "POSIXlt", FUN.VALUE = logical(1))
  value[is_posixlt] <- lapply(value[is_posixlt], as.POSIXct)
  value
}

#' Register a data frame as a virtual table
#'
#' `duckdb_register()` registers a data frame as a virtual table (view)
#'  in a DuckDB connection.
#'  No data is copied.
#'
#' `duckdb_unregister()` unregisters a previously registered data frame.
#' @param conn A DuckDB connection, created by `dbConnect()`.
#' @param name The name for the virtual table that is registered or unregistered
#' @param df A `data.frame` with the data for the virtual table
#' @param overwrite Should an existing registration be overwritten?
#' @param experimental Enable experimental optimizations
#' @return These functions are called for their side effect.
#' @export
#' @examples
#' con <- dbConnect(duckdb())
#'
#' data <- data.frame(a = 1:3, b = letters[1:3])
#'
#' duckdb_register(con, "data", data)
#' dbReadTable(con, "data")
#'
#' duckdb_unregister(con, "data")
#'
#' dbDisconnect(con)
duckdb_register <- function(conn, name, df, overwrite = FALSE, experimental = FALSE) {
  stopifnot(dbIsValid(conn))
  df <- encode_values(as.data.frame(df))
  rethrow_rapi_register_df(
    conn@conn_ref,
    enc2utf8(as.character(name)),
    df,
    duckdb_convert_opts_impl(conn@convert_opts, experimental = experimental),
    overwrite
  )
  invisible(TRUE)
}

#' @rdname duckdb_register
#' @export
duckdb_unregister <- function(conn, name) {
  rethrow_rapi_unregister_df(conn@conn_ref, enc2utf8(as.character(name)))
  invisible(TRUE)
}

#' Register an Arrow data source as a virtual table
#'
#' `duckdb_register_arrow()` registers an Arrow data source as a virtual table (view)
#'  in a DuckDB connection.
#'  No data is copied.
#'
#' `duckdb_unregister_arrow()` unregisters a previously registered data frame.
#' @param conn A DuckDB connection, created by `dbConnect()`.
#' @param name The name for the virtual table that is registered or unregistered
#' @param arrow_scannable A scannable Arrow-object
#' @param use_async Switched to the asynchronous scanner. (deprecated)
#' @return These functions are called for their side effect.
#' @export
duckdb_register_arrow <- function(conn, name, arrow_scannable, use_async = NULL) {
  stopifnot(dbIsValid(conn))

  if (!is.null(use_async)) {
    .Deprecated(msg = paste(
      "The parameter 'use_async' is deprecated",
      "and will be removed in a future release."
    ))
  }

  # create some R functions to pass to c-land
  export_fun <- function(arrow_scannable, stream_ptr, projection = NULL, filter = TRUE) {
    # If we get a scanner we must transform it to a record batch reader first
    if (class(arrow_scannable)[1] == "Scanner") {
      arrow_scannable <- arrow_scannable$ToRecordBatchReader()
    }
    arrow::Scanner$create(arrow_scannable, projection, filter)$ToRecordBatchReader()$export_to_c(stream_ptr)
  }

  get_schema_fun <- function(arrow_scannable, stream_ptr) {
    if (class(arrow_scannable)[1] == "arrow_dplyr_query") {
      collapse <- pkg_method("collapse", "dplyr")
      collapse(arrow_scannable)$.data$schema$export_to_c(stream_ptr)
    } else {
      arrow_scannable$schema$export_to_c(stream_ptr)
    }
  }

  # pass some functions to c land so we don't have to look them up there
  function_list <- list(
    export_fun,
    arrow::Expression$create,
    arrow::Expression$field_ref,
    arrow::Expression$scalar,
    get_schema_fun
  )

  rethrow_rapi_register_arrow(
    conn@conn_ref,
    enc2utf8(as.character(name)),
    function_list,
    arrow_scannable
  )
  invisible(TRUE)
}

#' @rdname duckdb_register_arrow
#' @export
duckdb_unregister_arrow <- function(conn, name) {
  rethrow_rapi_unregister_arrow(conn@conn_ref, enc2utf8(as.character(name)))
  invisible(TRUE)
}

#' @rdname duckdb_register_arrow
#' @export
duckdb_list_arrow <- function(conn) {
  sort(rethrow_rapi_list_arrow(conn@conn_ref))
}