Github user merrimanr commented on the issue:
https://github.com/apache/metron/pull/995
Let's say you want to add/remove/change a field in an existing document.
You would lookup the document, make your change, then reindex the document.
The problem is that expanded fields (polyfields) are returned when you lookup a
document. If you try to reindex those fields you will get an error.
This has more to do with field types than adding fields. The only way you
could cause a problem by adding a field is if you happened to add a field that
is a polyfield type that we are not handling. If we can put something in place
that handles all polyfield types, I think we're ok.
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