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From "Paul Rogers (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (DRILL-4181) Improve memory limit assignment for Sort operators
Date Wed, 30 Aug 2017 00:07:00 GMT

     [ https://issues.apache.org/jira/browse/DRILL-4181?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Paul Rogers reassigned DRILL-4181:

    Assignee: Paul Rogers

> Improve memory limit assignment for Sort operators
> --------------------------------------------------
>                 Key: DRILL-4181
>                 URL: https://issues.apache.org/jira/browse/DRILL-4181
>             Project: Apache Drill
>          Issue Type: Improvement
>    Affects Versions: 1.4.0
>            Reporter: Aman Sinha
>            Assignee: Paul Rogers
> Currently, the max_query_memory_per_node is divided among all the Sort operators in the
query plan, regardless of whether the Sort operators are executing at the same time.  Since
Sort is a blocking operator, the number of concurrent Sorts running is limited.  Thus, the
Sort on both sides of a MergeJoin could be concurrently executing but a Sort that occurs above
the MergeJoin cannot start until the MergeJoin produces a row which is only when both the
child Sorts have produced a row. 
> Due to the conservative estimate, we have seen queries such as TPC-H Q8 with forced MergeJoin
run out-of-memory even with high max_query_memory_per_node.  This query plan has 15 Sort operators
and with max_width = 23,  max_query_memory_per_node = 20GB, each Sort gets only  63MB (20GB/(23*15)).
   We should improve the algorithm for computing the memory limit. 

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