[GitHub] [drill] dzamo edited a comment on pull request #2283: DRILL-7979: Self-Closing XML Tags Cause Schema Change Exceptions

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dzamo edited a comment on pull request #2283:
URL: https://github.com/apache/drill/pull/2283#issuecomment-891086769


   Perhaps we should be trying for consistency with what Drill does with analogous JSON data.  Querying this document
   ```json
   [
   	{
   		"foo": null
   	},
   	{
   		"foo": { "bar": 0 }
   	}
   ]
   ```
   gives you 
   ```
   foo      |
   ---------|
   {}       |
   {"bar":0}|
   ```
   .  The null value becomes an empty map, as proposed for empty XML elements, but things are different to my earlier comment.  Adding an object with an int property `{"foo": 2}` returns an error, not a map with a special key `{'__value__' : 2 }`.  Changing that second object hold `"foo": [ 1, 2, 3 ]` makes the foo column an array.  Somehow Drill is able to delay its decision on the column type until the ocurrence of the first non-null value.  Is this something that's possible with Easy format plugins?


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