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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4539) Add support for Null Equality Joins
Date Thu, 14 Apr 2016 18:19:25 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15241672#comment-15241672

ASF GitHub Bot commented on DRILL-4539:

Github user amansinha100 commented on the pull request:

    I think additional support may be needed; the hash table only stores the equality join
keys, so the generated code in ChainedHashTable is targeted to the those columns.  For the
additional columns you will need to keep track of them (I haven't thought through the details

> 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`
>   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
> {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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