romainfrancois commented on a change in pull request #10730:
URL: https://github.com/apache/arrow/pull/10730#discussion_r672324588
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File path: r/src/altrep.cpp
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@@ -44,25 +49,58 @@ extern "C" {
#endif
#include <arrow/array.h>
+#include <arrow/util/bitmap_reader.h>
+
+#include "./r_task_group.h"
namespace arrow {
namespace r {
+template <typename T>
+void UseSentinel(const std::shared_ptr<Array>& array) {
Review comment:
Chances are we might need to implement something like this for arrays
that are backed by an immutable buffer, so maybe I can do that, and then we can
compare/measure and evaluate how risky this is.
Then we have 3 cases:
- Array with no nulls: best altrep with DATAPTR(), no need for setting
sentinels (what we had prior to this pull request).
- Array with some nulls, immutable: using GetRegion, I guess with a
materialized R vector in the data2 altrep slot, so that DATAPTR() materializes
and returns this.
- Array with some nulls, "mutable": hacky proposal of this pr.
Perhaps we only need the first 2.
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