Indhumathi27 commented on code in PR #6202:
URL: https://github.com/apache/hive/pull/6202#discussion_r2669025866
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ql/src/java/org/apache/hadoop/hive/ql/optimizer/LimitPushdownOptimizer.java:
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@@ -250,8 +255,12 @@ private static class LimitPushdownContext implements
NodeProcessorCtx {
private final float threshold;
+ private final boolean disallowRSCopy;
+
public LimitPushdownContext(HiveConf conf) throws SemanticException {
threshold =
conf.getFloatVar(HiveConf.ConfVars.HIVE_LIMIT_PUSHDOWN_MEMORY_USAGE);
+ disallowRSCopy =
conf.getBoolVar(HiveConf.ConfVars.HIVE_OPTIMIZE_TOPNKEY) &&
+ !conf.getBoolVar(HiveConf.ConfVars.HIVE_MAPSIDE_AGGREGATE);
Review Comment:
For query: `select value, sum(key) as sum from src group by value order by
value limit 20;`
when hive.map.aggr is true, tree stack has GBY[2] - RS[3] - GBY[4] - RS[6]
when hive.map.aggr is false, tree stack has RS[2] - GBY[2] - RS[5]
RS[2] here is Reduce output operator
Without patch: TopNkey will be applied for both operators.
With patch: TopNkey will be applied only to RS[5] operator.
There is no impact without this changes as well. RS[2] will have some of
configurations set, which comes in explain plan.
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