_search field added to mappings long before installing plugins

Hi all,

I'm having an issue with setting up the mapper-size plugin, specifically:
I have an ES instance that I've been upgrading since 6.x, now at 7.14. My mappings for my indices have always included:
"_size": {
"enabled": true

This was an early attempt to enable the _size field that was dropped and has now decided to turn on me.
Well, the mapping stayed, however, I never actually installed the mapping-size plugin on my nodes. That is, until today, when, upon restarting the service, I got a double definition error for the _size field:

MapperParsingException: Field [_size] is defined both as an object and a field

Aside from changing my index template mappings and reindexing (not an option), what chance have I got to get this working?

Unfortunately there is no way to delete field or field mapping from the index, and as you correctly identified only re-indexing can help.

Thank you for the quick feedback. That's what I figured the response would be but it's nice to get confirmation.