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#' @export
#' @rdname sql_build
select_query <- function(from,
select = sql("*"),
where = character(),
group_by = character(),
having = character(),
window = character(),
order_by = character(),
limit = NULL,
distinct = FALSE,
from_alias = NULL) {
check_character(select)
check_character(where)
check_character(group_by)
check_character(having)
check_character(window)
check_character(order_by)
check_number_whole(limit, allow_infinite = TRUE, allow_null = TRUE)
check_bool(distinct)
check_string(from_alias, allow_null = TRUE)
structure(
list(
from = from,
select = select,
where = where,
group_by = group_by,
having = having,
window = window,
order_by = order_by,
distinct = distinct,
limit = limit,
from_alias = from_alias
),
class = c("select_query", "query")
)
}
#' @export
print.select_query <- function(x, ...) {
cat_line("<SQL SELECT", if (x$distinct) " DISTINCT", ">")
cat_line("From:")
cat_line(indent_print(x$from))
if (length(x$select)) cat_line("Select: ", named_commas(x$select))
if (length(x$where)) cat_line("Where: ", named_commas(x$where))
if (length(x$group_by)) cat_line("Group by: ", named_commas(x$group_by))
if (length(x$window)) cat_line("Window: ", named_commas(x$window))
if (length(x$order_by)) cat_line("Order by: ", named_commas(x$order_by))
if (length(x$having)) cat_line("Having: ", named_commas(x$having)) # nocov
if (length(x$limit)) cat_line("Limit: ", x$limit)
}
#' @export
sql_optimise.select_query <- function(x, con = NULL, ..., subquery = FALSE) {
if (!inherits(x$from, "select_query")) {
return(x)
}
from <- sql_optimise(x$from, subquery = subquery)
# If all outer clauses are executed after the inner clauses, we
# can drop them down a level
outer <- select_query_clauses(x, subquery = subquery)
inner <- select_query_clauses(from, subquery = TRUE)
can_squash <- length(outer) == 0 || length(inner) == 0 || min(outer) > max(inner)
if (can_squash) {
# Have we optimised away an ORDER BY
if (length(from$order_by) > 0 && length(x$order_by) > 0) {
if (!identical(x$order_by, from$order_by)) {
warn_drop_order_by()
}
}
from[as.character(outer)] <- x[as.character(outer)]
from
} else {
x$from <- from
x
}
}
# List clauses used by a query, in the order they are executed
# https://sqlbolt.com/lesson/select_queries_order_of_execution
# List clauses used by a query, in the order they are executed in
select_query_clauses <- function(x, subquery = FALSE) {
present <- c(
where = length(x$where) > 0,
group_by = length(x$group_by) > 0,
having = length(x$having) > 0,
select = !identical(unname(x$select), sql("*")),
distinct = x$distinct,
window = length(x$window) > 0,
order_by = (!subquery || !is.null(x$limit)) && length(x$order_by) > 0,
limit = !is.null(x$limit)
)
ordered(names(present)[present], levels = names(present))
}
#' @export
sql_render.select_query <- function(query,
con,
...,
sql_options = NULL,
subquery = FALSE,
lvl = 0) {
from <- dbplyr_sql_subquery(con,
sql_render(query$from, con, ..., subquery = TRUE, lvl = lvl + 1),
name = query$from_alias,
lvl = lvl
)
dbplyr_query_select(
con, query$select, from,
where = query$where,
group_by = query$group_by,
having = query$having,
window = query$window,
order_by = query$order_by,
limit = query$limit,
distinct = query$distinct,
...,
subquery = subquery,
lvl = lvl
)
}
warn_drop_order_by <- function() {
# Rules according to SQLite: https://sqlite.org/forum/forumpost/878ca7a9be0862af?t=h
# 1. There is no LIMIT clause in the subquery
# 3. The subquery is not part of the FROM clause in an UPDATE-FROM statement
# 4. The outer query does not use any aggregate functions other than the built-in count(), min(), and/or max() functions.
# 5. Either the outer query has its own ORDER BY clause or else the subquery is one term of a join.
#
# (2. and 6. are left out as they are SQLite internal)
warn(c(
"ORDER BY is ignored in subqueries without LIMIT",
i = "Do you need to move arrange() later in the pipeline or use window_order() instead?"
))
}
#' @export
flatten_query.select_query <- function(qry, query_list, con) {
from <- qry$from
query_list <- flatten_query(from, query_list, con)
qry$from <- get_subquery_name(from, query_list)
querylist_reuse_query(qry, query_list, con)
}
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