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From "Suresh Ollala (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DRILL-4743) HashJoin's not fully parallelized in query plan
Date Mon, 25 Jul 2016 20:55:20 GMT

     [ https://issues.apache.org/jira/browse/DRILL-4743?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Suresh Ollala updated DRILL-4743:
---------------------------------
    Reviewer: Robert Hou

> HashJoin's not fully parallelized in query plan
> -----------------------------------------------
>
>                 Key: DRILL-4743
>                 URL: https://issues.apache.org/jira/browse/DRILL-4743
>             Project: Apache Drill
>          Issue Type: Bug
>    Affects Versions: 1.5.0
>            Reporter: Gautam Kumar Parai
>            Assignee: Gautam Kumar Parai
>              Labels: doc-impacting
>             Fix For: 1.8.0
>
>
> The underlying problem is filter selectivity under-estimate for a query with complicated
predicates e.g. deeply nested and/or predicates. This leads to under parallelization of the
major fragment doing the join. 
> To really resolve this problem we need table/column statistics to correctly estimate
the selectivity. However, in the absence of statistics OR even when existing statistics are
insufficient to get a correct estimate of selectivity this will serve as a workaround.



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