title: Should I reindex documents in Elasticsearch when I change the Stemmer?
body: <p>I am using Elasticsearch to index my documents (although I believe my question can apply to any other search engine such as Lucene or Solr as well).</p>
  
  <p>I am using Porter stemmer and a list of stop words at the index time. I know that I should apply the same stemmer and stop word removal at the search time to get correct results.</p>
  
  <p><strong>My question</strong> is that what if I decide to change my stemmer or add/remove couple of words to/from the list of stop words? <strong>Should I reindex all the documents</strong> (or all the text fields) to apply the changes? Or is there any other approach to deal with this situation?</p>