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Posted to issues@drill.apache.org by "Jacques Nadeau (JIRA)" <ji...@apache.org> on 2016/03/24 23:04:25 UTC
[jira] [Created] (DRILL-4539) Add support for Null Equality Joins
Jacques Nadeau created DRILL-4539:
-------------------------------------
Summary: 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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