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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4743) HashJoin's not fully parallelized in query plan
Date Fri, 15 Jul 2016 17:02:20 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15379687#comment-15379687

ASF GitHub Bot commented on DRILL-4743:

Github user amansinha100 commented on a diff in the pull request:

    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/server/options/SystemOptionManager.java
    @@ -251,7 +254,12 @@ public void setOption(final OptionValue value) {
         final String name = value.name.toLowerCase();
         final OptionValidator validator = getValidator(name);
    -    validator.validate(value); // validate the option
    +    /* If the validator depends on other options */
    +    if (validator instanceof DependentTypeValidators) {
    --- End diff --
    It would be good to avoid doing an instanceof (although sometimes it becomes unavoidable).
 Can you see what other changes are needed to achieve that ?  Seems like validate with a second
parameter can be implemented by DependentTypeValidators only and other validators could throw
an unsupported exception. 

> 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
> 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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