perf: another ExternalSorter refactor#21688

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mbutrovich wants to merge 12 commits intoapache:mainfrom

mbutrovich:externalsorter4

Commits on Apr 14, 2026

Rewrite ExternalSorter to coalesce batches before sorting, reducing merge fan-in. Subset of changes from #21600.
mbutrovich
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Simplify confusing logic.
mbutrovich
committed

Commits on Apr 15, 2026

Commits on Apr 17, 2026