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#' Backend: Teradata
#'
#' @description
#' See `vignette("translation-function")` and `vignette("translation-verb")` for
#' details of overall translation technology. Key differences for this backend
#' are:
#'
#' * Uses `TOP` instead of `LIMIT`
#' * Selection of user supplied translations
#'
#' Use `simulate_teradata()` with `lazy_frame()` to see simulated SQL without
#' converting to live access database.
#'
#' @name backend-teradata
#' @aliases NULL
#' @examples
#' library(dplyr, warn.conflicts = FALSE)
#'
#' lf <- lazy_frame(a = TRUE, b = 1, c = 2, d = "z", con = simulate_teradata())
#' lf %>% head()
NULL
#' @export
#' @rdname backend-teradata
simulate_teradata <- function() simulate_dbi("Teradata")
#' @export
dbplyr_edition.Teradata <- function(con) {
2L
}
#' @export
sql_query_select.Teradata <- function(con, select, from, where = NULL,
group_by = NULL, having = NULL,
window = NULL,
order_by = NULL,
limit = NULL,
distinct = FALSE,
...,
subquery = FALSE,
lvl = 0) {
sql_select_clauses(con,
select = sql_clause_select(con, select, distinct, top = limit),
from = sql_clause_from(from),
where = sql_clause_where(where),
group_by = sql_clause_group_by(group_by),
having = sql_clause_having(having),
window = sql_clause_window(window),
order_by = sql_clause_order_by(order_by, subquery, limit),
lvl = lvl
)
}
#' @export
sql_translation.Teradata <- function(con) {
sql_variant(
sql_translator(.parent = base_odbc_scalar,
`!=` = sql_infix("<>"),
bitwNot = sql_prefix("BITNOT", 1),
bitwAnd = sql_prefix("BITAND", 2),
bitwOr = sql_prefix("BITOR", 2),
bitwXor = sql_prefix("BITXOR", 2),
bitwShiftL = sql_prefix("SHIFTLEFT", 2),
bitwShiftR = sql_prefix("SHIFTRIGHT", 2),
as.numeric = function(x, digits = 9L) {
digits <- vctrs::vec_cast(digits, integer())
sql_expr(CAST(!!x %as% DECIMAL(12L, !!digits)))
},
as.double = sql_cast("NUMERIC"),
as.character = sql_cast("VARCHAR(MAX)"),
as.Date = function(x) {
build_sql("DATE ",x)
},
log10 = sql_prefix("LOG"),
log = sql_log(),
cot = sql_cot(),
quantile = sql_quantile("APPROX_PERCENTILE"),
median = sql_median("APPROX_PERCENTILE"),
nchar = sql_prefix("CHARACTER_LENGTH"),
ceil = sql_prefix("CEILING"),
ceiling = sql_prefix("CEILING"),
atan2 = function(x, y) {
sql_expr(ATAN2(!!y, !!x))
},
substr = function(x, start, stop) {
len <- stop - start + 1
sql_expr(SUBSTR(!!x, !!start, !!len))
},
startsWith = function(string, pattern) {
build_sql('CAST(CASE WHEN INSTR(',
string, ', ', pattern,
") = 1 THEN 1 ELSE 0 END AS INTEGER)")
},
paste = sql_paste_infix(" ", "||", function(x) sql_expr(!!x)),
paste0 = sql_paste_infix("", "||", function(x) sql_expr(!!x)),
row_number = win_rank_tdata("ROW_NUMBER"),
week = function(x){
sql_expr(WEEKNUMBER_OF_YEAR(!!x, 'iso'))
},
quarter = function(x) {
build_sql('to_char(',x,",'q')")
}
),
sql_translator(.parent = base_odbc_agg,
var = sql_aggregate("VAR_SAMP", "var"),
row_number = win_rank_tdata("ROW_NUMBER"),
weighted.mean = function(x, w, na.rm = T) {
# nocov start
win_over(
sql_expr(SUM((!!x * !!w))/SUM(!!w)),
win_current_group(),
win_current_group(),
win_current_frame()
)
# nocov end
}
),
sql_translator(.parent = base_odbc_win,
var = win_recycled("VAR_SAMP"),
row_number = win_rank_tdata("ROW_NUMBER"),
lead = function(x, n = 1L, default = NA, order_by = NULL) {
win_over(
sql_expr(LEAD(!!x, !!n, !!default)),
win_current_group(),
order_by %||% win_current_group(),
win_current_frame()
)
},
lag = function(x, n = 1L, default = NA, order_by = NULL) {
win_over(
sql_expr(LAG(!!x, !!as.integer(n), !!default)),
win_current_group(),
order_by %||% win_current_group(),
win_current_frame()
)
},
cumsum = function(x, order_by = NULL, frame = c(-Inf, 0)) {
win_over(
sql_expr(SUM(!!x)),
win_current_group(),
order_by %||% win_current_group(),
frame %||% win_current_frame()
)
},
weighted.mean = function(x, w, na.rm = T) {
# nocov start
win_over(
sql_expr(SUM((!!x * !!w))/SUM(!!w)),
win_current_group(),
win_current_group(),
win_current_frame()
)
# nocov end
}
)
)}
#' @export
sql_table_analyze.Teradata <- function(con, table, ...) {
# https://www.tutorialspoint.com/teradata/teradata_statistics.htm
build_sql("COLLECT STATISTICS ", as.sql(table, con = con) , con = con)
}
#' @export
supports_star_without_alias.Teradata <- function(con) {
FALSE
}
utils::globalVariables(c("ATAN2", "SUBSTR", "DECIMAL", "WEEKNUMBER_OF_YEAR", "SUM"))
#' @export
#' @rdname win_over
win_rank_tdata <- function(f) {
force(f)
function(order_by = NULL) {
order_by <- order_by %||% win_current_group()
if (is_empty(order_by)) order_by <- build_sql("(SELECT NULL)")
win_over(
build_sql(dplyr::sql(f), list()),
partition = win_current_group(),
order = order_by,
frame = win_current_frame()
)
}
}
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