title: ElasticSearch - How to merge indexes into one index?
body: <p>My cluster has an index for each day since a few months ago,
  5 shards each index (the default),
  and I can't run queries on the whole cluster because there are too many shards (over 1000).</p>
  
  <p>The document IDs are automatically generated.</p>
  
  <p>How can I combine the indexes into one index, deal with conflicting ids (if conflicts are even possible), and change the types?</p>
  
  <p>I am using ES version 5.2.1</p>