You should be able to change it without re-indexing, unless you've enabled docValues on that field. AFAIK docValues are the only persistent data structure that is different for single-valued versus multi-valued, everything else (UninvertedFields, etc) is built on the fly.
I don't think there's any definitive reference on what requires a re-index, but that would be a nice thing to add to the Reference Guide Alan Woodward www.flax.co.uk On 14 Oct 2014, at 08:30, Roger Sindreu wrote: > Hello > > I hope this question has not been asked many times. I did some research but > I never could find clearly answered anywhere. > > We have several multivalue fields on a instance with millions of documents > which only contain a single value. I would like to change it to > multivalue=false to be able to use grouping and stats on those fields. > > My question is: Can I do it without reindexing? > > Is there any document that says when rebuilding the index is needed versus > when it is not needed? > > Thanks a lot
