R/tbl-lazy.R

In tidyverse/dbplyr: A 'dplyr' Back End for Databases

#' Create a local lazy tibble
#'
#' These functions are useful for testing SQL generation without having to
#' have an active database connection. See [simulate_dbi()] for a list
#' available database simulations.
#'
#' @keywords internal
#' @export
#' @examples
#' library(dplyr)
#' df <- data.frame(x = 1, y = 2)
#'
#' df_sqlite <- tbl_lazy(df, con = simulate_sqlite())
#' df_sqlite %>% summarise(x = sd(x, na.rm = TRUE)) %>% show_query()
tbl_lazy <- function(df, con = NULL, ..., name = "df") {
  check_dots_empty0(...)
  con <- con %||% sql_current_con() %||% simulate_dbi()
  subclass <- class(con)[[1]]

  name <- as_table_path(name, con)

  dplyr::make_tbl(
    purrr::compact(c(subclass, "lazy")),
    lazy_query = lazy_base_query(df, names(df), class = "local", name = name),
    src = src_dbi(con)
  )
}
methods::setOldClass(c("tbl_lazy", "tbl"))

#' @export
#' @rdname tbl_lazy
lazy_frame <- function(..., con = NULL, .name = "df") {
  con <- con %||% sql_current_con() %||% simulate_dbi()
  tbl_lazy(tibble(...), con = con, name = .name)
}

#' @export
dimnames.tbl_lazy <- function(x) {
  list(NULL, op_vars(x$lazy_query))
}

#' @export
dim.tbl_lazy <- function(x) {
  c(NA, length(op_vars(x$lazy_query)))
}

#' @export
print.tbl_lazy <- function(x, ...) {
  show_query(x)
}

#' @export
as.data.frame.tbl_lazy <- function(x, row.names, optional, ...) {
  cli_abort("Can not coerce {.cls tbl_lazy} to {.cls data.frame}")
}

#' @importFrom dplyr same_src
#' @export
same_src.tbl_lazy <- function(x, y) {
  inherits(y, "tbl_lazy")
}

#' @importFrom dplyr tbl_vars
#' @export
tbl_vars.tbl_lazy <- function(x) {
  op_vars(x$lazy_query)
}

#' @importFrom dplyr groups
#' @export
groups.tbl_lazy <- function(x) {
  lapply(group_vars(x), as.name)
}

# nocov start
#' @exportS3Method dplyr::group_by_drop_default
group_by_drop_default.tbl_lazy <- function(x) {
  TRUE
}
# nocov end

#' @importFrom dplyr group_vars
#' @export
group_vars.tbl_lazy <- function(x) {
  op_grps(x$lazy_query)
}

is_tbl_lazy <- function(x) {
  inherits(x, "tbl_lazy")
}

#' @importFrom tidyselect tidyselect_data_proxy tidyselect_data_has_predicates
#' @export
tidyselect_data_proxy.tbl_lazy <- function(x) {
  vars <- op_vars(x)
  out <- as_tibble(rep_named(vars, list(logical())), .name_repair = "minimal")
  group_by(out, !!!syms(group_vars(x)))
}

#' @export
tidyselect_data_has_predicates.tbl_lazy <- function(x) {
  FALSE
}

the <- new_environment()
the$warned_on_tbl_lazy_names <- FALSE

#' @export
names.tbl_lazy <- function(x) {
  should_inform <- rlang::env_is_user_facing(rlang::caller_env())
  if (should_inform) {
    cli::cli_inform(c(
      `!` = "The {.fn names} method of {.cls tbl_lazy} is for internal use only.",
      i = "Did you mean {.fn colnames}?"
    ))
  }
  NextMethod("names")
}

#' @export
`$.tbl_lazy` <- function(x, name) {
  unexpected_name <- !name %in% c("lazy_query", "src")

  if (unexpected_name) {
    cli::cli_abort(c(
      "The `$` method of {.cls tbl_lazy} is for internal use only.",
      i = "Use {.fn dplyr::pull} to get the values in a column."
    ))
  }
  NextMethod("$")
}