[jira] [Assigned] (SPARK-24013) ApproximatePercentile grinds to a halt on sorted input.

["Apache Spark (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-24013?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Apache Spark reassigned SPARK-24013:
------------------------------------

    Assignee: Apache Spark

> ApproximatePercentile grinds to a halt on sorted input.
> -------------------------------------------------------
>
>                 Key: SPARK-24013
>                 URL: https://issues.apache.org/jira/browse/SPARK-24013
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 2.3.0
>            Reporter: Juliusz Sompolski
>            Assignee: Apache Spark
>            Priority: Major
>         Attachments: screenshot-1.png
>
>
> Running
> {code}
> sql("select approx_percentile(rid, array(0.1)) from (select rand() as rid from range(10000000))").collect()
> {code}
> takes 7 seconds, while
> {code}
> sql("select approx_percentile(id, array(0.1)) from range(10000000)").collect()
> {code}
> grinds to a halt - processes the first million rows quickly, and then slows down to a few thousands rows / second (4m rows processed after 20 minutes).
> Thread dumps show that it spends time in QuantileSummary.compress.
> Seems it hits some edge case inefficiency when dealing with sorted data?



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