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#' Backend: Redshift
#'
#' @description
#' Base translations come from [PostgreSQL backend][simulate_postgres]. There
#' are generally few differences, apart from string manipulation.
#'
#' Use `simulate_redshift()` with `lazy_frame()` to see simulated SQL without
#' converting to live access database.
#'
#' @name backend-redshift
#' @aliases NULL
#' @examples
#' library(dplyr, warn.conflicts = FALSE)
#'
#' lf <- lazy_frame(a = TRUE, b = 1, c = 2, d = "z", con = simulate_redshift())
#' lf %>% transmute(x = paste(c, " times"))
#' lf %>% transmute(x = substr(c, 2, 3))
#' lf %>% transmute(x = str_replace_all(c, "a", "z"))
NULL
#' @export
#' @rdname backend-redshift
simulate_redshift <- function() simulate_dbi("RedshiftConnection")
#' @export
dbplyr_edition.RedshiftConnection <- function(con) {
2L
}
#' @export
dbplyr_edition.Redshift <- dbplyr_edition.RedshiftConnection
redshift_round <- function(x, digits = 0L) {
digits <- as.integer(digits)
sql_expr(round(((!!x)) %::% float, !!digits))
}
#' @export
sql_translation.RedshiftConnection <- function(con) {
postgres <- sql_translation.PostgreSQL(con)
sql_variant(
sql_translator(.parent = postgres$scalar,
# https://docs.aws.amazon.com/redshift/latest/dg/r_Numeric_types201.html#r_Numeric_types201-floating-point-types
as.numeric = sql_cast("FLOAT"),
as.double = sql_cast("FLOAT"),
round = redshift_round,
# https://stackoverflow.com/questions/56708136
paste = sql_paste_redshift(" "),
paste0 = sql_paste_redshift(""),
str_c = sql_paste_redshift(""),
# https://docs.aws.amazon.com/redshift/latest/dg/r_SUBSTRING.html
substr = sql_substr("SUBSTRING"),
substring = sql_substr("SUBSTRING"),
str_sub = sql_str_sub("SUBSTRING", "LEN"),
# https://docs.aws.amazon.com/redshift/latest/dg/REGEXP_REPLACE.html
str_replace = sql_not_supported("str_replace"),
str_replace_all = function(string, pattern, replacement) {
sql_expr(REGEXP_REPLACE(!!string, !!pattern, !!replacement))
},
# clock ---------------------------------------------------------------
add_days = function(x, n, ...) {
check_dots_empty()
sql_expr(DATEADD(DAY, !!n, !!x))
},
add_years = function(x, n, ...) {
check_dots_empty()
sql_expr(DATEADD(YEAR, !!n, !!x))
},
date_build = function(year, month = 1L, day = 1L, ..., invalid = NULL) {
glue_sql2(sql_current_con(), "TO_DATE(CAST({.val year} AS TEXT) || '-' CAST({.val month} AS TEXT) || '-' || CAST({.val day} AS TEXT)), 'YYYY-MM-DD')")
},
get_year = function(x) {
sql_expr(DATE_PART('year', !!x))
},
get_month = function(x) {
sql_expr(DATE_PART('month', !!x))
},
get_day = function(x) {
sql_expr(DATE_PART('day', !!x))
},
difftime = function(time1, time2, tz, units = "days") {
if (!missing(tz)) {
cli::cli_abort("The {.arg tz} argument is not supported for SQL backends.")
}
if (units[1] != "days") {
cli::cli_abort('The only supported value for {.arg units} on SQL backends is "days"')
}
sql_expr(DATEDIFF(DAY, !!time1, !!time2))
}
),
sql_translator(.parent = postgres$aggregate,
# https://docs.aws.amazon.com/redshift/latest/dg/r_LISTAGG.html
str_flatten = function(x, collapse = "") {
sql_expr(LISTAGG(!!x, !!collapse))
}
),
sql_translator(.parent = postgres$window,
# https://docs.aws.amazon.com/redshift/latest/dg/r_WF_LAG.html
lag = function(x, n = 1L, order_by = NULL) {
win_over(
sql_expr(LAG(!!x, !!as.integer(n))),
win_current_group(),
order_by %||% win_current_order(),
win_current_frame()
)
},
# https://docs.aws.amazon.com/redshift/latest/dg/r_WF_LEAD.html
lead = function(x, n = 1L, order_by = NULL) {
win_over(
sql_expr(LEAD(!!x, !!as.integer(n))),
win_current_group(),
order_by %||% win_current_order(),
win_current_frame()
)
},
# https://docs.aws.amazon.com/redshift/latest/dg/r_LISTAGG.html
str_flatten = function(x, collapse = "") {
order <- win_current_order()
listagg_sql <- sql_expr(LISTAGG(!!x, !!collapse))
if(length(order) > 0){
sql <- glue_sql2(
sql_current_con(),
"{listagg_sql} WITHIN GROUP (ORDER BY {order})"
)
} else {
sql <- listagg_sql
}
win_over(
sql,
partition = win_current_group()
# Cannot use the order here because LISTAGG requires the ordering in the
# WITHIN GROUP (ORDER BY ...) clause
)
}
)
)
}
#' @export
sql_translation.Redshift <- sql_translation.RedshiftConnection
sql_paste_redshift <- function(sep) {
sql_paste_infix(sep, "||", function(x) sql_expr(cast(!!x %as% text)))
}
# https://docs.aws.amazon.com/redshift/latest/dg/r_EXPLAIN.html
#' @export
sql_query_explain.Redshift <- function(con, sql, ...) {
glue_sql2(con, "EXPLAIN {sql}")
}
#' @export
sql_query_explain.RedshiftConnection <- sql_query_explain.Redshift
#' @export
sql_values_subquery.Redshift <- function(con, df, types, lvl = 0, ...) {
sql_values_subquery_union(con, df, types = types, lvl = lvl)
}
#' @export
sql_values_subquery.RedshiftConnection <- sql_values_subquery.Redshift
#' @export
supports_window_clause.Redshift <- function(con) {
FALSE
}
#' @export
supports_window_clause.RedshiftConnection <- supports_window_clause.Redshift
utils::globalVariables(c("REGEXP_REPLACE", "LAG", "LEAD", "LISTAGG", "float", "text", "DATE_PART"))
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