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From "Jinfeng Ni (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-5546) Schema change problems caused by empty batch
Date Mon, 05 Jun 2017 18:00:06 GMT

    [ https://issues.apache.org/jira/browse/DRILL-5546?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16037290#comment-16037290

Jinfeng Ni commented on DRILL-5546:

Thanks for putting a set of form definitions of terms, which would clear confusion.

In current Drill execution and as well as in this proposal, *NONE* simply means the end of
input; there is no more batch coming. It should not be used to represent any batch. The Drill's
iterator framework has the code to handle 'NONE'.  This proposal is just to suggest we return
*NONE* directly, if the data source does not have any schema/data.  This is different from
what currently Drill is doing: return a *OK_NEW_SCHEMA* with a trivial result set (injected
with nullable-int column), followed by a 'NONE'.  

Using the notation you defined, previously Drill has 

{{protocol : (OK_NEW_SCHEMA OK\*)\+ NONE}}

Now we have:

{{protocol : (OK_NEW_SCHEMA OK\*)\* NONE}}

Some operators seems to work fine under the protocol change, some operators such as Join,
UnionAll may not, due to the above protocol changes.   

> Schema change problems caused by empty batch
> --------------------------------------------
>                 Key: DRILL-5546
>                 URL: https://issues.apache.org/jira/browse/DRILL-5546
>             Project: Apache Drill
>          Issue Type: Bug
>            Reporter: Jinfeng Ni
>            Assignee: Jinfeng Ni
> There have been a few JIRAs opened related to schema change failure caused by empty batch.
This JIRA is opened as an umbrella for all those related JIRAS ( such as DRILL-4686, DRILL-4734,
DRILL4476, DRILL-4255, etc).

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