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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, 22 Jul 2016 20:45:20 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15390165#comment-15390165
] 

ASF GitHub Bot commented on DRILL-4743:
---------------------------------------

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

    https://github.com/apache/drill/pull/534#discussion_r71942925
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/compile/QueryClassLoader.java
---
    @@ -44,8 +44,8 @@
       public static final String JAVA_COMPILER_OPTION = "exec.java_compiler";
       public static final StringValidator JAVA_COMPILER_VALIDATOR = new StringValidator(JAVA_COMPILER_OPTION,
CompilerPolicy.DEFAULT.toString()) {
         @Override
    -    public void validate(OptionValue v) {
    -      super.validate(v);
    +    public void validate(OptionValue v, OptionManager manager) {
    --- End diff --
    
    final ?


> 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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