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https://issues.apache.org/jira/browse/DRILL-4081?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15006151#comment-15006151
 ] 

ASF GitHub Bot commented on DRILL-4081:
---------------------------------------

Github user jacques-n commented on a diff in the pull request:

    https://github.com/apache/drill/pull/257#discussion_r44883694
  
    --- Diff: 
exec/vector/src/main/java/org/apache/drill/exec/vector/complex/FieldIdUtil.java 
---
    @@ -121,4 +125,63 @@ public static TypedFieldId 
getFieldIdIfMatches(ValueVector vector, TypedFieldId.
           }
         }
       }
    +
    +  public static TypedFieldId getFieldId(ValueVector vector, int id, 
SchemaPath expectedPath, boolean hyper) {
    --- End diff --
    
    Is it possible to share this code (or much of it with getFieldIdIfMatches() 
above). It seems like they are related (although I didn't go line by line)


> Handle schema changes in ExternalSort
> -------------------------------------
>
>                 Key: DRILL-4081
>                 URL: https://issues.apache.org/jira/browse/DRILL-4081
>             Project: Apache Drill
>          Issue Type: Improvement
>            Reporter: Steven Phillips
>            Assignee: Steven Phillips
>
> This improvement will make use of the Union vector to handle schema changes. 
> When a new schema appears, the schema will be "merged" with the previous 
> schema. The result will be a new schema that uses Union type to store the 
> columns where this is a type conflict. All of the batches (including the 
> batches that have already arrived) will be coerced into this new schema.
> A new comparison function will be included to handle the comparison of Union 
> type. Comparison of union type will work as follows:
> 1. All numeric types can be mutually compared, and will be compared using 
> Drill implicit cast rules.
> 2. All other types will not be compared against other types, but only among 
> values of the same type.
> 3. There will be an overall precedence of types with regards to ordering. 
> This precedence is not yet defined, but will be as part of the work on this 
> issue.



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