[jira] [Assigned] (HIVE-16496) Enhance asterisk expression (as in "select *") with EXCLUDE clause

["Nikhil Harsoor (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-16496?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Nikhil Harsoor reassigned HIVE-16496:
-------------------------------------

    Assignee:     (was: Nikhil Harsoor)

> Enhance asterisk expression (as in "select *") with EXCLUDE clause
> ------------------------------------------------------------------
>
>                 Key: HIVE-16496
>                 URL: https://issues.apache.org/jira/browse/HIVE-16496
>             Project: Hive
>          Issue Type: Wish
>          Components: Parser
>            Reporter: Dudu Markovitz
>            Priority: Major
>
> support the following syntax:
> {code}
> select * exclude (a,b,e) from t
> {code}
> which for a table t with columns a,b,c,d,e would be equal to:
> {code}
> select c,d from t
> {code}
> Please note that the EXCLUDE clause relates directly to its preceding asterisk.
> Here are some useful use cases:
> h3. use-case 1: join
> {code}
> select t1.* exclude (x), t2.* from t1 join t2 on t1.x=t2.x;
> {code}
> This supplies a very clean way to select all columns without getting "Ambiguous column reference" and without the need to specify all the columns of at least one of the tables.
>  
> Currently, without this enhancement, the query would look something like this:
> {code}
> select a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,y,z,t2.* from t1 join t2 on t1.x=t2.x;
> {code}
> Considering a table may hold hundreds or even thousands of column, this can be come very ugly and error prone.
> Often this require some scripting work.
> h3. use-case 2: view
> Creating views with all the tables columns except for some technical columns
>  
> {code}
> create myview as select * exclude (cre_ts,upd_ts) from t;
> {code}
> h3. use-case 3: row_number
> Remove computational columns that are not needed in the final row-set, e.g. -
> retrieve the last record for each customer
> {code}
> select  * exclude (rn)
> from   (select  t.*
>                ,row_number() over (partition by customer_id order by ts desc) as rn
>         from    t
>         ) t
>         
> where   rn = 1
> {code}



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