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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4539) Add support for Null Equality Joins
Date Fri, 15 Apr 2016 21:30:25 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15243693#comment-15243693
] 

ASF GitHub Bot commented on DRILL-4539:
---------------------------------------

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

    https://github.com/apache/drill/pull/462#discussion_r59943901
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/common/HashTableConfig.java
---
    @@ -22,25 +22,36 @@
     import com.fasterxml.jackson.annotation.JsonCreator;
     import com.fasterxml.jackson.annotation.JsonProperty;
     import com.fasterxml.jackson.annotation.JsonTypeName;
    +import org.apache.drill.exec.physical.impl.join.JoinUtils.JoinComparator;
     
     @JsonTypeName("hashtable-config")
     public class HashTableConfig  {
     
    -  static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(HashTableConfig.class);
    -
       private final int initialCapacity;
       private final float loadFactor;
       private final NamedExpression[] keyExprsBuild;
       private final NamedExpression[] keyExprsProbe;
    +  private final JoinComparator[] comparators;
     
       @JsonCreator
       public HashTableConfig(@JsonProperty("initialCapacity") int initialCapacity, @JsonProperty("loadFactor")
float loadFactor,
                              @JsonProperty("keyExprsBuild") NamedExpression[] keyExprsBuild,
    -                         @JsonProperty("keyExprsProbe") NamedExpression[] keyExprsProbe)
{
    +                         @JsonProperty("keyExprsProbe") NamedExpression[] keyExprsProbe,
    +                         @JsonProperty("comparators") JoinComparator[] comparators) {
         this.initialCapacity = initialCapacity;
         this.loadFactor = loadFactor;
         this.keyExprsBuild = keyExprsBuild;
         this.keyExprsProbe = keyExprsProbe;
    +    if (comparators != null) {
    +      this.comparators = comparators;
    +    } else {
    +      // default is nulls are equal
    --- End diff --
    
    Agree, it is clean to remove passing null and explicitly pass a value to comparator. Updated
patch. Also renamed join.JoinComparator to common.Comparator.


> Add support for Null Equality Joins
> -----------------------------------
>
>                 Key: DRILL-4539
>                 URL: https://issues.apache.org/jira/browse/DRILL-4539
>             Project: Apache Drill
>          Issue Type: Improvement
>            Reporter: Jacques Nadeau
>            Assignee: Venki Korukanti
>
> Tableau frequently generates queries similar to this:
> {code}
> SELECT `t0`.`city` AS `city`,
>   `t2`.`X_measure__B` AS `max_Calculation_DFIDBHHAIIECCJFDAG_ok`,
>   `t0`.`state` AS `state`,
>   `t0`.`sum_stars_ok` AS `sum_stars_ok`
> FROM (
>   SELECT `business`.`city` AS `city`,
>     `business`.`state` AS `state`,
>     SUM(`business`.`stars`) AS `sum_stars_ok`
>   FROM `mongo.academic`.`business` `business`
>   GROUP BY `business`.`city`,
>     `business`.`state`
> ) `t0`
>   INNER JOIN (
>   SELECT MAX(`t1`.`X_measure__A`) AS `X_measure__B`,
>     `t1`.`city` AS `city`,
>     `t1`.`state` AS `state`
>   FROM (
>     SELECT `business`.`city` AS `city`,
>       `business`.`state` AS `state`,
>       `business`.`business_id` AS `business_id`,
>       SUM(`business`.`stars`) AS `X_measure__A`
>     FROM `mongo.academic`.`business` `business`
>     GROUP BY `business`.`city`,
>       `business`.`state`,
>       `business`.`business_id`
>   ) `t1`
>   GROUP BY `t1`.`city`,
>     `t1`.`state`
> ) `t2` ON (((`t0`.`city` = `t2`.`city`) OR ((`t0`.`city` IS NULL) AND (`t2`.`city` IS
NULL))) AND ((`t0`.`state` = `t2`.`state`) OR ((`t0`.`state` IS NULL) AND (`t2`.`state` IS
NULL))))
> {code}
> If you look at the join condition, you'll note that the join condition is an equality
condition which also allows null=null. We should add a planning rewrite rule and execution
join option to allow null equality so that we don't treat this as a cartesian join.



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