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From "Harish Butani (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-4197) Bring windowing support inline with SQL Standard
Date Mon, 18 Mar 2013 22:25:15 GMT

    [ https://issues.apache.org/jira/browse/HIVE-4197?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13605743#comment-13605743
] 

Harish Butani commented on HIVE-4197:
-------------------------------------

Ashutosh, thanks for reviewing.

- agree with you on Partition/Order expressions, Boundary amount deviations from Standard.

- Stable order issue:
It is not just restricted to when no order is specified. It also crops up when 2 rows have
the same value on the Order expressions. This affects  the window frame and processing of
functions that dependent on the order(rank,dense_rank...)
One thought is to add the FileName and FileOffset virtual columns to the Order Spec. 

Source Window Spec:
as I understand this, it is the ability to reference another Window definition in the Query
and inherit components from it. For e.g.

{noformat}
select a,b, rank() over (w1 unbounded preceding and current row),
from xyz
window w1 (partition by x order by y)
{noformat}

The effective window spec for rank() is:
{noformat}
rank() over (partition by x order by y w1 unbounded preceding and current row)
{noformat}

The rule we have adopted is that each component Partition, Order, WindowFrame is independently
inherited from a source Window Spec. Inheritance happens only if that component is not defined.
As I said in the doc, it is not clear to me what the spec is mandating here.

- Agree with your other points. 
1. The way we have Range Windows is confusing. Should associate it with the Order expression
2. Don't see the point of allowing Windows on Lead, Lag, Rank etc.So then Jira 4192 can be
resolved as '.working as designed'
3. Lead/Lag UDFs will keep it in for now; but may remove if it becomes hard to maintain
                
> Bring windowing support inline with SQL Standard
> ------------------------------------------------
>
>                 Key: HIVE-4197
>                 URL: https://issues.apache.org/jira/browse/HIVE-4197
>             Project: Hive
>          Issue Type: Bug
>          Components: PTF-Windowing
>            Reporter: Harish Butani
>         Attachments: WindowingSpecification.pdf
>
>
> The current behavior defers from the Standard in several significant places.
> Please review attached doc; there are still a few open issues. Once we agree on the behavior,
can proceed with fixing the implementation.

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