How to perform a search query in Elasticsearch

Elasticsearch provides a powerful Query DSL that supports both structured and full-text searches, allowing precise retrieval of documents based on various criteria.

Queries range from simple match queries to complex bool queries, enabling flexible filtering, scoring, and boosting of documents. Aggregations complement the search process by revealing patterns, terms, and statistical insights.

By mastering the Query DSL, administrators and developers can transform raw data into meaningful information, guiding data-driven decisions and improving the search experience.

1. Confirm the target index exists and is available for querying.
2. Choose the index and the fields you want to query.
3. Use a POST request to the _search endpoint with a JSON query body.

   $ curl --request POST --header "Content-Type: application/json" --data '{
     "query": {
       "match": {
         "title": "example"
       }
     }
   }' http://localhost:9200/my_index/_search
   
   {"took":5,"timed_out":false,"hits":{"total":{"value":1,"relation":"eq"},"hits":[{"_index":"my_index","_id":"1","_source":{"title":"example doc"}}]}}

   A match query analyzes the text; use a term query for exact matches.

4. Examine the JSON response for hits and verify the returned documents.
5. Add aggregations to explore patterns in the data.

   $ curl --request POST --header "Content-Type: application/json" --data '{
     "aggs": {
       "titles_count": {
         "value_count": {
           "field": "title"
         }
       }
     }
   }' http://localhost:9200/my_index/_search
   
   {"took":5,"aggregations":{"titles_count":{"value":10}}}

   Aggregations provide metrics, histograms, and term distributions.

6. Refine queries by adding filters, sorting, or pagination as needed.

   Complex queries may require careful indexing and mapping for optimal performance.