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https://issues.apache.org/jira/browse/IMPALA-5004?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16680041#comment-16680041
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Sahil Takiar commented on IMPALA-5004:
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[~arodoni_cloudera] filed IMPALA-7836
> Switch to sorting node for large TopN queries
> ---------------------------------------------
>
> Key: IMPALA-5004
> URL: https://issues.apache.org/jira/browse/IMPALA-5004
> Project: IMPALA
> Issue Type: Improvement
> Components: Frontend
> Affects Versions: Impala 2.9.0
> Reporter: Lars Volker
> Assignee: Sahil Takiar
> Priority: Major
> Fix For: Impala 3.1.0
>
>
> As explained by [~tarmstrong] in IMPALA-4995:
> bq. We should also consider switching to the sort operator for large limits.
> This allows it to spill. The memory requirements for TopN also are
> problematic for large limits, since it would allocate large vectors that are
> untracked and also require a large amount of contiguous memory.
> There's already logic to select TopN vs. Sort:
> [planner/SingleNodePlanner.java#L289|https://github.com/apache/incubator-impala/blob/master/fe/src/main/java/org/apache/impala/planner/SingleNodePlanner.java#L289]
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