[jira] [Commented] (ORC-789) Supporting schema evolution for union expansion

["Ratandeep Ratti (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ORC-789?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17566471#comment-17566471 ] 

Ratandeep Ratti commented on ORC-789:
-------------------------------------

Hi Lei, to simplify... can we reduce the error to something like ?

```

writer schema: uniontype<struct<a:double, b:double>>

reader schema: uniontype<struct<a:double, b:double>, double>

```

 

> Supporting schema evolution for union expansion
> -----------------------------------------------
>
>                 Key: ORC-789
>                 URL: https://issues.apache.org/jira/browse/ORC-789
>             Project: ORC
>          Issue Type: Improvement
>            Reporter: Lei Sun
>            Assignee: Lei Sun
>            Priority: Major
>
> We are seeing the following schema evolution occurred from time to time while ORC library doesn't seem to support that: 
> {code:java}
> Error: org.apache.orc.impl.SchemaEvolution$IllegalEvolutionException: ORC does not support type conversion from file type uniontype<(obfuscated List of columns),struct<correctPin:string,userInput:string>> to reader type uniontype<(obfuscated List of columns),struct<correctPin:string,userInput:string>,struct<version:string>>
> {code}
> We would like to add the support. 
>  



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