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#' spec_arrow_get_query_arrow
#' @family Arrow specifications
#' @usage NULL
#' @format NULL
#' @keywords NULL
spec_arrow_get_query_arrow <- list(
arrow_get_query_arrow_formals = function() {
# <establish formals of described functions>
expect_equal(names(formals(dbGetQueryArrow)), c("conn", "statement", "..."))
},
arrow_get_query_arrow_atomic = function(con) {
#' @return
#' `dbGetQueryArrow()` always returns an object coercible to a [data.frame], with
#' as many rows as records were fetched and as many
#' columns as fields in the result set,
#' even if the result is a single value
query <- trivial_query()
rows <- check_arrow(dbGetQueryArrow(con, query))
expect_equal(rows, data.frame(a = 1.5))
},
arrow_get_query_arrow_one_row = function(con) {
#' or has one
query <- trivial_query(3, letters[1:3])
result <- trivial_df(3, letters[1:3])
rows <- check_arrow(dbGetQueryArrow(con, query))
expect_identical(rows, result)
},
arrow_get_query_arrow_zero_rows = function(ctx, con) {
skip_if_not_dbitest(ctx, "1.8.0.12")
#' or zero rows.
# Not all SQL dialects seem to support the query used here.
query <-
"SELECT * FROM (SELECT 1 as a, 2 as b, 3 as c) AS x WHERE (1 = 0)"
rows <- check_arrow(dbGetQueryArrow(con, query))
expect_identical(names(rows), letters[1:3])
expect_identical(dim(rows), c(0L, 3L))
},
#'
arrow_get_query_arrow_closed_connection = function(ctx, closed_con) {
#' @section Failure modes:
#' An error is raised when issuing a query over a closed
expect_error(dbGetQueryArrow(closed_con, trivial_query()))
},
arrow_get_query_arrow_invalid_connection = function(ctx, invalid_con) {
#' or invalid connection,
expect_error(dbGetQueryArrow(invalid_con, trivial_query()))
},
arrow_get_query_arrow_syntax_error = function(con) {
#' if the syntax of the query is invalid,
expect_error(dbGetQueryArrow(con, "SELLECT"))
},
arrow_get_query_arrow_non_string = function(con) {
#' or if the query is not a non-`NA` string.
expect_error(dbGetQueryArrow(con, character()))
expect_error(dbGetQueryArrow(con, letters))
expect_error(dbGetQueryArrow(con, NA_character_))
},
arrow_get_query_arrow_record_batch_reader = function(ctx, con) {
#' The object returned by `dbGetQueryArrow()` can also be passed to
#' [nanoarrow::as_nanoarrow_array_stream()] to create a nanoarrow
#' array stream object that can be used to read the result set
#' in batches.
query <- trivial_query(25, .ctx = ctx, .order_by = "a")
result <- trivial_df(25)
stream <- dbGetQueryArrow(con, query)
rbr <- nanoarrow::as_nanoarrow_array_stream(stream)
#' The chunk size is implementation-specific.
out <- as.data.frame(rbr$get_next())
expect_equal(out, head(result, nrow(out)))
},
#' @section Additional arguments:
#' The following arguments are not part of the `dbGetQueryArrow()` generic
#' (to improve compatibility across backends)
#' but are part of the DBI specification:
#' - `params` (default: `NULL`)
#' - `immediate` (default: `NULL`)
#'
#' They must be provided as named arguments.
#' See the "Specification" and "Value" sections for details on their usage.
#'
arrow_get_query_arrow_params = function(ctx, con) {
skip_if_not_dbitest(ctx, "1.8.0.1")
#' The `param` argument allows passing query parameters, see [dbBind()] for details.
placeholder_funs <- get_placeholder_funs(ctx)
for (placeholder_fun in placeholder_funs) {
placeholder <- placeholder_fun(1)
query <- paste0("SELECT ", placeholder, " + 1.0 AS a")
values <- trivial_values(3) - 1
params <- stats::setNames(list(values), names(placeholder))
ret <- dbGetQueryArrow(con, query, params = params)
expect_equal(as.data.frame(ret), trivial_df(3), info = placeholder)
}
},
#
arrow_get_query_arrow_immediate = function(ctx, con, table_name) {
skip_if_not_dbitest(ctx, "1.8.0.2")
#' @section Specification for the `immediate` argument:
#'
#' The `immediate` argument supports distinguishing between "direct"
#' and "prepared" APIs offered by many database drivers.
#' Passing `immediate = TRUE` leads to immediate execution of the
#' query or statement, via the "direct" API (if supported by the driver).
#' The default `NULL` means that the backend should choose whatever API
#' makes the most sense for the database, and (if relevant) tries the
#' other API if the first attempt fails. A successful second attempt
#' should result in a message that suggests passing the correct
#' `immediate` argument.
#' Examples for possible behaviors:
#' 1. DBI backend defaults to `immediate = TRUE` internally
#' 1. A query without parameters is passed: query is executed
#' 1. A query with parameters is passed:
#' 1. `params` not given: rejected immediately by the database
#' because of a syntax error in the query, the backend tries
#' `immediate = FALSE` (and gives a message)
#' 1. `params` given: query is executed using `immediate = FALSE`
#' 1. DBI backend defaults to `immediate = FALSE` internally
#' 1. A query without parameters is passed:
#' 1. simple query: query is executed
#' 1. "special" query (such as setting a config options): fails,
#' the backend tries `immediate = TRUE` (and gives a message)
#' 1. A query with parameters is passed:
#' 1. `params` not given: waiting for parameters via [dbBind()]
#' 1. `params` given: query is executed
res <- expect_visible(dbGetQueryArrow(con, trivial_query(), immediate = TRUE))
check_arrow(res)
},
#
NULL
)
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