paleolimbot commented on code in PR #279:
URL: https://github.com/apache/arrow-nanoarrow/pull/279#discussion_r1300212953
##########
r/R/convert-array-stream.R:
##########
@@ -62,26 +68,52 @@ convert_array_stream <- function(array_stream, to = NULL,
size = NULL, n = Inf)
)
}
+ # Collect all batches into a list()
+ batches <- collect_array_stream(
+ array_stream,
+ n,
+ schema = schema,
+ validate = FALSE
+ )
+
+ # If there is exactly one batch, use convert_array()
+ if (length(batches) == 1L) {
+ return(.Call(nanoarrow_c_convert_array, batches[[1]], to))
+ }
+
+ # Otherwise, compute the final size, create another array stream,
+ # and call convert_array_stream() with a known size.
+ lengths <- vapply(
+ batches,
+ # Use custom accessor because array$length in a loop is slow
+ function(array) {
+ .Call(nanoarrow_c_array_proxy, array, NULL, FALSE)$length
+ },
+ double(1)
+ )
+ basic_stream <- .Call(nanoarrow_c_basic_array_stream, batches, schema, FALSE)
+ convert_array_stream(basic_stream, to = to, size = sum(lengths))
+}
+
+#' @rdname convert_array_stream
+#' @export
+collect_array_stream <- function(array_stream, n = Inf, schema = NULL,
+ validate = TRUE) {
+ stopifnot(
+ inherits(array_stream, "nanoarrow_array_stream")
+ )
+
+ if (is.null(schema)) {
+ schema <- .Call(nanoarrow_c_array_stream_get_schema, array_stream)
+ }
+
batches <- vector("list", 1024L)
n_batches <- 0L
get_next <- array_stream$get_next
- while (!is.null(array <- get_next(schema, validate = FALSE)) && (n_batches <
n)) {
+ while (!is.null(array <- get_next(schema, validate = validate)) &&
(n_batches < n)) {
Review Comment:
Done!
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