elasticsearchHow can I join two Elasticsearch indices?

Joining two Elasticsearch indices is possible by using the search_after parameter. It allows you to search for documents after a certain document. The following example code block shows how to join two indices:

# First search
response1 = Elasticsearch::Client.search index: 'index1', body: {
  query: {
    match: {
      field1: 'value1'
    }
  },
  sort: [
    {
      _id: 'asc'
    }
  ]
}

# Second search
response2 = Elasticsearch::Client.search index: 'index2', body: {
  query: {
    match: {
      field2: 'value2'
    }
  },
  search_after: response1['hits']['hits'].last['_id']
}

This will return the documents from the first index (index1) sorted by the _id field, and then the documents from the second index (index2) sorted by the _id field after the last document from the first index.

Parts of the code explained:

• response1: The first search request which searches for documents in index1 and sorts them by the _id field.
• response2: The second search request which searches for documents in index2 and sorts them by the _id field after the last document from index1. The search_after parameter is used here to specify the last document from index1.
• response1['hits']['hits'].last['_id']: This is used to get the _id of the last document from index1 which is used as the search_after parameter in the second search request.

Helpful links

• Elasticsearch search_after parameter
• Elasticsearch Client

Edit this code on GitHub