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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 17:51:20 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15379781#comment-15379781
] 

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

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

    https://github.com/apache/drill/pull/534#discussion_r71013627
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/server/options/TypeValidators.java
---
    @@ -27,6 +27,21 @@
     import static com.google.common.base.Preconditions.checkArgument;
     
     public class TypeValidators {
    +
    +  /** Interface implemented by option validators which depend on other options
    +   *  in order to perform validation. e.g. MIN/MAX option validators might be
    +   *  dependent if MIN should always be less than MAX.
    +   *
    +   */
    +  public interface DependentTypeValidators
    +  {
    +    /* Interface method requires providing an OptionManager which can
    +     * be used to read option values of dependencies. As an example look at
    +     * MinRangeDoubleValidator/MaxRangeDoubleValidator
    +     */
    +    public void validate(OptionValue v, BaseOptionManager manager);
    --- End diff --
    
    Would replacing `validate(OptionValue)` with `validate(OptionValue, OptionManager)` in
the `OptionValidator` interface work?


> 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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