zabetak commented on code in PR #6202:
URL: https://github.com/apache/hive/pull/6202#discussion_r2664769990
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ql/src/java/org/apache/hadoop/hive/ql/optimizer/topnkey/TopNKeyProcessor.java:
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@@ -111,6 +123,50 @@ public Object process(Node nd, Stack<Node> stack,
NodeProcessorCtx procCtx,
return null;
}
+ /**
+ * Returns true if the ReduceSink is only under an ORDER BY + LIMIT plan
+ * and has no GroupBy or Join operators in its upstream ancestry.
+ * This is used to disable TopNKey for pure ORDER BY LIMIT queries where
+ * LIMIT pushdown must take precedence.
+ */
+ public static boolean isOrderByLimitPath(ReduceSinkOperator rs) {
Review Comment:
If there is no GBY/JOIN below the RS (that is PTF) do we gain something by
creating the TopNKey operator? In other words is the TopNKey operator more
efficient than the topn filtering in the RS?
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