So along the lines of why does this need to happen, what needs to happen? I see that the reindex API is the recommended method, but this looks like a utility that just copies one index to another. I could be wrong, but I don't see how that could fix any problem. I could just map a "new" index that matches my old one and use a data transfer utility.
So what is the actual problem I am trying to solve here? I have several indices that were made in 2.3, that are not in 5.5. I want to be able to look at them and know where the issue will be.
Thank you for any info/links on this.