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model: fix iobuf over-reservation for null key/value records #30980

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WillemKauf merged 1 commit into from
Jul 1, 2026
Merged

model: fix iobuf over-reservation for null key/value records #30980

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4 changes: 3 additions & 1 deletion src/v/model/record_utils.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -225,7 +225,9 @@ void append_record_to_buffer(iobuf& a, const model::record& r) {
append_vint_to_iobuf(a, r.timestamp_delta());
append_vint_to_iobuf(a, r.offset_delta());

a.reserve_memory(r.key_size() + r.value_size());
auto key_bytes = std::max(r.key_size(), 0);

@StephanDollberg StephanDollberg Jul 1, 2026

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Why do these methods return -1 and not 0?

@WillemKauf WillemKauf Jul 1, 2026

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-1 is used to distinguish a key/value in a record that is empty (std::nullopt) versus having a key/value that has a length of 0 ("").

@StephanDollberg StephanDollberg Jul 1, 2026

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Back to 1999

auto val_bytes = std::max(r.value_size(), 0);
a.reserve_memory(key_bytes + val_bytes);
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WillemKauf marked this conversation as resolved.
append_vint_to_iobuf(a, r.key_size());
if (r.key_size() > 0) {
for (auto& f : r.key()) {
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