ES 2.2 Add/remove stop word asks for rebuild. Is this really necessary?

[Mr Lucky]

Just adding or removing a single word from stop words causes a message telling me I need to rebuild the index

Is this absolutely necessary?

What will happen if I don't?

 

[briansol]

old content will not be changed, only new posts will be indexed without the stop words. So, you should rebuild the index if the intent is to remove the stop word.

 

[Mr Lucky]

old content will not be changed, only new posts will be indexed without the stop words. So, you should rebuild the index if the intent is to remove the stop word.

However if I add a stop word, and do not rebuild the cache, then that word is not serached and show results for either old threads or new ones since the word.

ie it seems to work on all threads whether cache is rebuilt or not.