[jira] [Created] (DRILL-1311) Hash join does not support schema changes error

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

Neeraja created DRILL-1311:
------------------------------

             Summary: Hash join does not support schema changes error
                 Key: DRILL-1311
                 URL: https://issues.apache.org/jira/browse/DRILL-1311
             Project: Apache Drill
          Issue Type: Bug
            Reporter: Neeraja


- Create a directory with a couple of JSON files. One with columns a,b and second with columns a,b,c. 
- a & b attributes have same data types across both the files
- create a view by selecting columns a, b from the directory
- Join the view with any other table

An error shows up indicating that 'Hash join does not support schema changes'.
There is a schema change across the files with a new element being added, however given that specific columns a,b are selected in the view, expect that query works fine.



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Re: [jira] [Created] (DRILL-1311) Hash join does not support schema changes error

[Jinfeng Ni <ji...@gmail.com>]

If possible, can you post the physical plan for the join query you tried?

W/o seeing the plan, all I can guess is that this SchemaChange error might
be related to Project Pushdown. Currently, Drill does not support project
pushdown for JSON storage. As a result, all the columns will be retrieved
from the storage, and given to the parent operator, HashJoin, which will
see SchemaChange, since one file contains 2 columns, and the other one
contains 3 columns.

There is a patch on the way to support Project pushdown for JSON. Once that
patch is merged, it probably will solve this issue.




On Mon, Aug 18, 2014 at 6:04 PM, Neeraja (JIRA) <ji...@apache.org> wrote:

> Neeraja created DRILL-1311:
> ------------------------------
>
>              Summary: Hash join does not support schema changes error
>                  Key: DRILL-1311
>                  URL: https://issues.apache.org/jira/browse/DRILL-1311
>              Project: Apache Drill
>           Issue Type: Bug
>             Reporter: Neeraja
>
>
> - Create a directory with a couple of JSON files. One with columns a,b and
> second with columns a,b,c.
> - a & b attributes have same data types across both the files
> - create a view by selecting columns a, b from the directory
> - Join the view with any other table
>
> An error shows up indicating that 'Hash join does not support schema
> changes'.
> There is a schema change across the files with a new element being added,
> however given that specific columns a,b are selected in the view, expect
> that query works fine.
>
>
>
> --
> This message was sent by Atlassian JIRA
> (v6.2#6252)
>