[jira] [Assigned] (ASTERIXDB-1500) Inject filters to eliminate null/missing join keys for equality joins

["Yingyi Bu (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ASTERIXDB-1500?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Yingyi Bu reassigned ASTERIXDB-1500:
------------------------------------

    Assignee: Dmitry Lychagin  (was: Yingyi Bu)

> Inject filters to eliminate null/missing join keys for equality joins
> ---------------------------------------------------------------------
>
>                 Key: ASTERIXDB-1500
>                 URL: https://issues.apache.org/jira/browse/ASTERIXDB-1500
>             Project: Apache AsterixDB
>          Issue Type: Improvement
>          Components: COMP - Compiler
>            Reporter: Yingyi Bu
>            Assignee: Dmitry Lychagin
>              Labels: soon
>
> For the following query, there could be many tweets that has the field in_reply_to_status_id being null/missing. Therefore, that would skewness of for the hash join.  Since this is an inner join and missing/null join keys anyway could not produce qualified join results, the optimizer should inject null/missing filters before the join.
> {noformat}
> FROM Tweets t2 JOIN Tweets t1 ON t2.in_reply_to_status_id = t1.id
> WHERE not(`is-unknown`(t2.in_reply_to_status_id))
> GROUP BY t1.id AS id, t1.user.name AS name, t1.text AS text
> SELECT id, name, text, COUNT(t2) AS num_retweets
> ORDER BY num_retweets DESC
> LIMIT 5;
> {noformat}



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