[v26.1.x] compaction: swap std::count() for cursor approach (MANUAL BACKPORT) - #30760
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WillemKauf merged 2 commits intoJun 11, 2026
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When records are removed, the filter rebuilds the batch and, for each record, ran `std::count` over the kept-deltas vector to decide whether to keep it, which is quadratic in the record count. Since the kept deltas are produced by a forward scan of the same batch, they are already in record-iteration order, so match each record with a single advancing cursor instead. (cherry picked from commit f1458b8)
Mirror the shared filter change in `copy_data_segment_reducer::filter`: the rebuild path matched each record against the kept-deltas vector with `std::count`, which is quadratic in the record count. The kept deltas are produced by a forward scan of the same batch, so match with a single advancing cursor instead, guarded by a `dassert` on the ordering invariant. (cherry picked from commit d9b0f9e)
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Manual backport of #30740.
cherry-pickconflict due to rearrangedmaintenancedirectory indev. Dropped benchmark file additions.Fixes #30759.
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