hive-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Navis (JIRA)" <>
Subject [jira] [Commented] (HIVE-6189) Support top level union all statements
Date Wed, 15 Jan 2014 01:49:19 GMT


Navis commented on HIVE-6189:

I'm pretty sure Harish is more proficient than me for this kind of works. Good to hear that
hive supports top level union! 

> Support top level union all statements
> --------------------------------------
>                 Key: HIVE-6189
>                 URL:
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Gunther Hagleitner
>            Assignee: Gunther Hagleitner
>         Attachments: HIVE-6189.1.patch, HIVE-6189.2.patch, HIVE-6189.3.patch
> I've always wondered why union all has to be in subqueries in hive.
> After looking at it, problems are:
> - Hive Parser:
>   - Union happens at the wrong place (insert ... select ... union all select ...) is
parsed as (insert select) union select.
>   - There are many rewrite rules in the parser to force any query into the a from - insert
-select form. No doubt for historical reasons.
> - Plan generation/semantic analysis assumes top level "TOK_QUERY" and not top level "TOK_UNION".
> The rewrite rules don't work when we move the "UNION ALL" recursion into the select statements.
However, it's not hard to do that in code.

This message was sent by Atlassian JIRA

View raw message