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https://issues.apache.org/jira/browse/DRILL-4743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15342825#comment-15342825
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ASF GitHub Bot commented on DRILL-4743:
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GitHub user gparai opened a pull request:
https://github.com/apache/drill/pull/534
[DRILL-4743] HashJoin's not fully parallelized in query plan
Provide a user parameter for defining a lower bound of selectivity to
prevent under-estimates on filter selectivity.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/gparai/drill MD-880-ADM
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/drill/pull/534.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #534
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----
> 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
>
> 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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