Multi Index Search | Advanced Search | Elasticsearch Tutorial

Introduction

Elasticsearch is a powerful search engine that allows for full-text search, structured search, and analytics. One of the advanced features of Elasticsearch is the ability to perform searches across multiple indices. This is useful in scenarios where data is spread across different indices, and a unified search view is required.

Understanding Multi-Index Search

In Elasticsearch, an index is a collection of documents. Multi-index search allows you to query multiple indices at once. This can be done by specifying multiple index names in the search request or using wildcards to match multiple indices.

Basic Multi-Index Search

To perform a basic multi-index search, you can simply list the indices in the search request. For example, to search across two indices named index1 and index2, you can use the following query:

GET /index1,index2/_search
{
  "query": {
    "match_all": {}
  }
}

This query will return all documents from both index1 and index2.

Using Wildcards for Multi-Index Search

Elasticsearch supports the use of wildcards in index names. This allows you to search across multiple indices that match a certain pattern. For example, if you have indices named log-2021-01, log-2021-02, and so on, you can search across all these indices using a wildcard:

GET /log-2021-*/_search
{
  "query": {
    "match_all": {}
  }
}

This query will match all indices that start with log-2021- and return documents from all these indices.

Advanced Multi-Index Search

Elasticsearch allows you to perform more advanced multi-index searches by combining different query types. For example, you can use a bool query to combine multiple conditions:

GET /index1,index2/_search
{
  "query": {
    "bool": {
      "must": [
        { "match": { "field1": "value1" }},
        { "range": { "date": { "gte": "2021-01-01" }}}
      ]
    }
  }
}

This query will search across index1 and index2 for documents that match field1:value1 and have a date greater than or equal to 2021-01-01.

Handling Results from Multi-Index Searches

When you perform a multi-index search, the results will include documents from all the specified indices. The response will indicate the index each document came from. Here is an example response:

{
  "took": 10,
  "timed_out": false,
  "_shards": {
    "total": 10,
    "successful": 10,
    "failed": 0
  },
  "hits": {
    "total": {
      "value": 100,
      "relation": "eq"
    },
    "max_score": 1.0,
    "hits": [
      {
        "_index": "index1",
        "_type": "_doc",
        "_id": "1",
        "_score": 1.0,
        "_source": {
          "field1": "value1",
          "date": "2021-01-02"
        }
      },
      {
        "_index": "index2",
        "_type": "_doc",
        "_id": "2",
        "_score": 1.0,
        "_source": {
          "field1": "value2",
          "date": "2021-01-03"
        }
      }
    ]
  }
}

In this response, you can see that the _index field indicates the index from which each document was retrieved.

Conclusion

Multi-index search in Elasticsearch is a powerful feature that allows you to query data across multiple indices efficiently. By understanding the basics and advanced usage of multi-index search, you can leverage Elasticsearch to perform comprehensive searches across your datasets.

Multi-Index Search in Elasticsearch