Reindexing using same fields

[vinay_khandelwal]

Hello,

I am trying to reindex a large index into a smaller one by filtering . However I would like to retain some of the metadata with a different field name then used in the original index. "_source" allows me to copy over fields as it is. How can have some of the fields renamed while reindexing?

POST _reindex
{
  "source": {
    "index": ["logstash-2016.09.11","logstash-2016.09.12"],
    "_source": ["_type","timestamp","machid"],
     "query": {
      "term": {
        "_type": "DCA_OBC"
      }
    }
  },
  "dest": {
    "index": "docs_a"
  },
   "script": {
    "inline": "ctx._source.gid = doc[_id]",
    "lang": "painless"
  }
}

Can I use the painless script in similar form as shown above, to achieve the same? Here gid is the new field name to store the _id of previous index. I want to give this document a new id on reindexing and save the previous one as gid too.

Thanks