storage-controller: reuse DatumVec when truncating status history#36991
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The handle_row closure in partially_truncate_status_history decoded each snapshot row with Row::unpack, allocating a fresh Vec<Datum> per row in the hot truncation loop. Capture a re-used DatumVec in the closure and decode via borrow_with instead, which returns the allocation to the vector on drop and reuses it across rows.
martykulma
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Jun 11, 2026
martykulma
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martykulma
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lgtm, thanks @antiguru !
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Motivation
The
handle_rowclosure inpartially_truncate_status_historydecoded each snapshot row withRow::unpack, which allocates a freshVec<Datum>on every call. This runs in the hot per-row truncation loop over the status history shard.This is a sibling change to the metrics-history truncation PR (#36990); same pattern, different call site.
Tips for reviewer
The closure now captures a re-used
DatumVecand decodes rows viaborrow_with, which returns its allocation to the vector on drop and reuses it across rows.extract_key/extract_timetake&[Datum], and&DatumVecBorrowderef-coerces to&[Datum], so the call sites are unchanged. The closure was alreadymut/FnMut(it mutateslatest_row_per_key), so capturing theDatumVecby value and borrowing it mutably is fine.Checklist
$T ⇔ Proto$Tmapping (possibly in a backwards-incompatible way), then it is tagged with aT-protolabel.Generated by Claude Code