[jira] [Assigned] (HIVE-3773) Share input scan by unions across multiple queries

["Gang Tim Liu (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-3773?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Gang Tim Liu reassigned HIVE-3773:
----------------------------------

    Assignee: Gang Tim Liu  (was: Namit Jain)
    
> Share input scan by unions across multiple queries
> --------------------------------------------------
>
>                 Key: HIVE-3773
>                 URL: https://issues.apache.org/jira/browse/HIVE-3773
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: Gang Tim Liu
>
> Consider a query like:
> select * from
> (
>   select key, 1 as value, count(1) from src group by key
>     union all
>   select 1 as key, value, count(1) from src group by value
>     union all
>   select key, value, count(1) from src group by key, value
> ) s;
> src is scanned multiple times currently (one per sub-query).
> This should be treated like a multi-table insert by the optimizer.

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