konstantinb commented on code in PR #6331:
URL: https://github.com/apache/hive/pull/6331#discussion_r3028993053
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ql/src/java/org/apache/hadoop/hive/ql/optimizer/stats/annotation/StatsRulesProcFactory.java:
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@@ -3080,6 +3114,65 @@ public Object process(Node nd, Stack<Node> stack,
NodeProcessorCtx procCtx,
return null;
}
+
+ /**
+ * Refines UDTF column statistics using LVJ's context and defensive
identity mapping.
+ */
+ private void refineUdtfColStats(List<ColStatistics> udtfColStats,
Review Comment:
the "refine" idea was to provide better statistics than "estimated many
things unknown" ColStatistics for those UDFTs that have determinmistic
semantics, and to leave generic ones for others.
> Explode/posexplode have deterministic semantics allowing NDV inference
from input. Other UDTFs lack this property.
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