The docs (https://www.elastic.co/guide/en/elasticsearch/reference/current/similarity) and announcement blog post (https://www.elastic.co/blog/elasticsearch-5-0-0-released) seem to disagree about the new default similarity. Is it classic or BM25?
I think you may have got a stale version of that page when you looked before. The page has moved slightly and the documentation you link to now 404s for me due to that. Take a look at the new location of the doucmentation here which agrees with the blog post that the default is BM25: https://www.elastic.co/guide/en/elasticsearch/reference/5.0/index-modules-similarity.html#_available_similarities
There is a glitch on https://www.elastic.co/guide/en/elasticsearch/reference/5.0/similarity.html
still stating that default similarity is
Oh, well spotted @jprante, I'll raise it on the ES Repo. Thanks
I raised https://github.com/elastic/elasticsearch/pull/21144 to fix this, Thanks both for raising this