Elastic Search merge two indices

Question

Reindex cannot be used to merge two indices. Reindex does a complete update in the destination index.

Consider the below index my-new-index-000001:

GET my-new-index-000001/_doc/6

{
  "_index" : "my-new-index-000001",
  "_type" : "_doc",
  "_id" : "6",
  "_version" : 26,
  "_seq_no" : 34,
  "_primary_term" : 16,
  "found" : true,
  "_source" : {
    "field2" : "value2",
    "field1" : "value1"
  }
}

The above index had two fields field1 and field2.

The below snippet is used to reindex a source field (new_field) to the destination:

# reindex that field
POST _reindex
{
  "source": {
    "index": ["my-index-000001"],
    "query": {
      "terms": {
        "_id": [6]
      }
    },
    "_source":["new_field"]
  },
  "dest": {
    "index": "my-new-index-000001"
  }
}

After reindexing this is the updated my-new-index-000001 index

GET my-new-index-000001/_doc/6

{
  "_index" : "my-new-index-000001",
  "_type" : "_doc",
  "_id" : "6",
  "_version" : 27,
  "_seq_no" : 35,
  "_primary_term" : 16,
  "found" : true,
  "_source" : {
    "new_field" : false
  }
}

Is there a way to do partial update in Elastic search from source to destination based on a common field? Is there a way to achieve this using python script. Please share a working snippet or reference.

Answer 1

you can use Update By Query API.

https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-update-by-query.html