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#' Create an SQL tbl (abstract)
#'
#' Generally, you should no longer need to provide a custom `tbl()`
#' method.
#' The default `tbl.DBIConnect` method should work in most cases.
#'
#' @keywords internal
#' @export
#' @param subclass name of subclass
#' @param ... needed for agreement with generic. Not otherwise used.
#' @param vars Provide column names as a character vector
#' to avoid retrieving them from the database.
#' Mainly useful for better performance when creating
#' multiple `tbl` objects.
tbl_sql <- function(subclass, src, from, ..., vars = NULL) {
# If not literal sql, must be a table identifier
from_sql <- as.sql(from, con = src$con)
if (!(is.ident(from) || is.sql(from) || is_schema(from))) {
from <- as.sql(from, con = src$con)
}
vars <- vars %||% dbplyr_query_fields(src$con, from_sql)
tbl_sql_impl(subclass, src, from, vars)
}
tbl_sql_impl <- function(subclass, src, from, vars) {
dplyr::make_tbl(
c(subclass, "sql", "lazy"),
src = src,
lazy_query = lazy_query_remote(from, vars)
)
}
#' @importFrom dplyr same_src
#' @export
same_src.tbl_sql <- function(x, y) {
inherits(y, "tbl_sql") && same_src(x$src, y$src)
}
# Grouping methods -------------------------------------------------------------
#' @importFrom dplyr group_size
#' @export
group_size.tbl_sql <- function(x) {
df <- x %>%
summarise(n = n()) %>%
collect()
df$n
}
#' @importFrom dplyr n_groups
#' @export
n_groups.tbl_sql <- function(x) {
if (length(groups(x)) == 0) return(1L)
df <- x %>%
summarise() %>%
ungroup() %>%
summarise(n = n()) %>%
collect()
df$n
}
# Standard data frame methods --------------------------------------------------
#' @export
print.tbl_sql <- function(x, ..., n = NULL, width = NULL, n_extra = NULL) {
cat_line(format(x, ..., n = n, width = width, n_extra = n_extra))
invisible(x)
}
#' @export
as.data.frame.tbl_sql <- function(x, row.names = NULL, optional = NULL,
..., n = Inf) {
as.data.frame(collect(x, n = n))
}
#' @export
#' @importFrom tibble tbl_sum
tbl_sum.tbl_sql <- function(x) {
tbl_sum_tbl_sql(x)
}
tbl_sum_tbl_sql <- function(x, desc = tbl_desc(x)) {
grps <- op_grps(x$lazy_query)
sort <- op_sort(x$lazy_query)
c(
"Source" = desc,
"Database" = dbplyr_connection_describe(x$src$con),
"Groups" = if (length(grps) > 0) commas(grps),
"Ordered by" = if (length(sort) > 0) commas(deparse_all(sort))
)
}
tbl_desc <- function(x, rows_total = NA_integer_) {
paste0(
op_desc(x$lazy_query),
" [",
op_rows(x$lazy_query, rows_total),
" x ",
big_mark(op_cols(x$lazy_query)),
"]"
)
}
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