[fix](nereids) Gate aggregate parent shuffle reuse by NDV stats#64892
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[fix](nereids) Gate aggregate parent shuffle reuse by NDV stats#64892foxtail463 wants to merge 2 commits into
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run buildall |
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TPC-H: Total hot run time: 29420 ms |
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TPC-DS: Total hot run time: 171785 ms |
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ClickBench: Total hot run time: 25.24 s |
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run buildall |
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TPC-H: Total hot run time: 28727 ms |
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TPC-DS: Total hot run time: 171183 ms |
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ClickBench: Total hot run time: 25.15 s |
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FE Regression Coverage ReportIncrement line coverage |
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Problem Summary:
PhysicalHashAggregate could still enumerate a parent hash key that is only a strict subset of the group by keys when child statistics were missing or unknown. That allowed CBO to choose a narrower shuffle distribution without evidence that the parent key had enough NDV, which can concentrate data and lead to OOM.
Solution:
Require agg_shuffle_use_parent_key to pass a real stats gate before adding the parent subset distribution: child stats and parent key stats must be known, and the estimated parent-key group count must be greater than LOW_NDV_THRESHOLD. Keep the full group key distribution as the conservative fallback.