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https://issues.apache.org/jira/browse/TRAFODION-2259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15546967#comment-15546967
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ASF GitHub Bot commented on TRAFODION-2259:
-------------------------------------------
Github user DaveBirdsall commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/743#discussion_r81870590
--- Diff: core/sql/sort/SortUtil.cpp ---
@@ -170,6 +174,22 @@ NABoolean SortUtil::sortInitialize(SortUtilConfig&
config)
&sortError_,
explainNodeId_,
this);
+ }
+ else
+ {
+ sortAlgo_ =
+ new (config.heapAddr_) TopN(config.topNSize_,
+
config.maxMem_,
--- End diff --
Again, tabbing problems?
> Sort TopN operator
> ------------------
>
> Key: TRAFODION-2259
> URL: https://issues.apache.org/jira/browse/TRAFODION-2259
> Project: Apache Trafodion
> Issue Type: Improvement
> Components: sql-exe
> Affects Versions: 2.1-incubating
> Reporter: Prashanth Vasudev
> Assignee: Prashanth Vasudev
>
> Sort operator consumes all records before producing sorted records. For
> certain use cases where only Top N records are required, today sort consumes
> all records into memory and overflows( spills ) to disk. This impacts
> performance.
> if topN is pushed down to sort, only required memory can be allocated and
> sort would only hold topN records in memory. Once all the records are read,
> sorted records in topN is returned.
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