EmilyMatt commented on code in PR #19494:
URL: https://github.com/apache/datafusion/pull/19494#discussion_r2650634092
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datafusion/physical-plan/src/sorts/sort.rs:
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@@ -813,22 +829,14 @@ impl ExternalSorter {
}
/// Estimate how much memory is needed to sort a `RecordBatch`.
-///
-/// This is used to pre-reserve memory for the sort/merge. The sort/merge
process involves
-/// creating sorted copies of sorted columns in record batches for speeding up
comparison
-/// in sorting and merging. The sorted copies are in either row format or
array format.
-/// Please refer to cursor.rs and stream.rs for more details. No matter what
format the
-/// sorted copies are, they will use more memory than the original record
batch.
-pub(crate) fn get_reserved_byte_for_record_batch_size(record_batch_size:
usize) -> usize {
- // 2x may not be enough for some cases, but it's a good start.
- // If 2x is not enough, user can set a larger value for
`sort_spill_reservation_bytes`
- // to compensate for the extra memory needed.
- record_batch_size * 2
-}
-
-/// Estimate how much memory is needed to sort a `RecordBatch`.
-fn get_reserved_byte_for_record_batch(batch: &RecordBatch) -> usize {
-
get_reserved_byte_for_record_batch_size(get_record_batch_memory_size(batch))
+/// This is calculated by adding the record batch's memory size
+/// (which can be much larger than expected for sliced record batches)
+/// with the sliced buffer sizes, as that is the amount that will be needed to
create the new buffer.
+/// The latter is rounded up to the nearest multiple of 64 based on the
architecture,
+/// as this is how arrow creates buffers.
Review Comment:
Fine by me, updated.
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