zanmato1984 commented on code in PR #41335:
URL: https://github.com/apache/arrow/pull/41335#discussion_r1598791898
##########
cpp/src/arrow/compute/row/compare_internal.h:
##########
@@ -32,6 +32,13 @@ namespace compute {
class ARROW_EXPORT KeyCompare {
public:
+ // Clarify the max temp stack usage for CompareColumnsToRows so the caller
could reserve
+ // enough size in advance.
+ constexpr static int64_t CompareColumnsToRowsTempStackUsage(int64_t
num_rows) {
+ return (sizeof(uint8_t) + sizeof(uint8_t) + sizeof(uint8_t)) * num_rows +
Review Comment:
They correspond to:
https://github.com/apache/arrow/blob/a715ea06b71ec206a987d7921264778e9954404b/cpp/src/arrow/compute/row/compare_internal.cc#L342-L347
Will add more comment on this.
> Also, elsewhere we multiple by kMiniBatchLength but here it seems we are
adding kMiniBatchLength. Why the difference?
The idea is to keep extra `kMiniBatchLength` bytes (to cope with stack
aligning and padding) anyhow. Elsewhere using multiply is because the other
parts are all in unit of `kMiniBatchLength` but this one is special - multiple
of `num_rows` which can be arbitrary.
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