fix(scorch): serialize merge task execution - #2
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ajroetker merged 1 commit intoJul 24, 2026
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Execute merge plan tasks sequentially, matching upstream behavior. Concurrent tasks multiply transient disk staging because every in-flight output remains live and ineligible for garbage collection until the whole plan is introduced. Serial execution bounds staging to one task at a time and allows cancellation to take effect between tasks. Merge planner size and task-count defaults remain unchanged.
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Summary
Root cause
The AntflyDB fork parallelized the tasks within a merge plan. Each in-flight task output is correctly considered live and ineligible for garbage collection until the plan is introduced. During deterministic merge retry storms, task concurrency therefore multiplies transient disk staging and the collector cannot safely reclaim it.
Serial execution restores upstream behavior and bounds staging to one task footprint at a time.
Scope
This PR intentionally changes only task execution. It does not change MaxSegmentFileSize, SegmentsPerMergeTask, or any other planner tuning, and it does not add merge logging.
Validation
Related incident: antflydb/antfly#381