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https://issues.apache.org/jira/browse/HIVE-12866?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15270517#comment-15270517
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Ashutosh Chauhan commented on HIVE-12866:
-----------------------------------------
We have entirely disabled RS-dedup in presence of constants, it will be nice if
we can restore this optimization.
> Allow ReduceSinkDeDuplication to kick in when there are constant keys
> ----------------------------------------------------------------------
>
> Key: HIVE-12866
> URL: https://issues.apache.org/jira/browse/HIVE-12866
> Project: Hive
> Issue Type: Bug
> Reporter: Hari Sankar Sivarama Subramaniyan
>
> Currently in ReduceSinkDeDuplication.checkExprs() we have the following check
> which prevents the optimization from kicking in as soon as we hit constant
> key. We should lift this restriction as much as possible.
> {code}
> private Integer checkExprs(List<ExprNodeDesc> ckeys, List<ExprNodeDesc>
> pkeys,
> ReduceSinkOperator cRS, ReduceSinkOperator pRS) throws
> SemanticException {
> // If ckeys or pkeys have constant node expressions avoid the merge.
> for (ExprNodeDesc ck : ckeys) {
> if (ck instanceof ExprNodeConstantDesc) {
> return null;
> }
> }
> for (ExprNodeDesc pk : pkeys) {
> if (pk instanceof ExprNodeConstantDesc) {
> return null;
> }
> }
> {code}
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