javaelasticsearchspring-dataspring-data-elasticsearch

How do i return only selected fields

I need a query where i select only 1 field, not the entire documents. How do i do that?

I have this query:

NativeQuery query = NativeQuery
        .builder()
        .withMaxResults(100)
        .withQuery(...))
        .withFields("the_field_i_need")
        .build();

SearchHits<T> searchHits = operations.search(query, MyEntity.class, "my-index");

But i cannot figure out how to return the field "the_field_i_need" and ignore all other fields

Solution

  • If you want to retrieve only specific fields instead of the entire document, you can use the FetchSourceFilter to include or exclude fields. Here's how you can modify your code:

    import org.springframework.data.elasticsearch.core.SearchHit;
import org.springframework.data.elasticsearch.core.SearchHits;
import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
import org.springframework.data.elasticsearch.core.query.NativeQuery;
import org.springframework.data.elasticsearch.core.query.NativeSearchQueryBuilder;
import org.springframework.data.elasticsearch.core.query.NativeSearchQuery;

// ...

NativeSearchQuery query = new NativeSearchQueryBuilder()
        .withQuery(...)  // Add your query here
        .withMaxResults(100)
        .withSourceFilter(new FetchSourceFilter(new String[]{"the_field_i_need"}, null))
        .build();

SearchHits<MyEntity> searchHits = elasticsearchRestTemplate.search(query, MyEntity.class, IndexCoordinates.of("my-index"));

    In this example, FetchSourceFilter is used to specify the fields to include ("the_field_i_need") and exclude (null in this case, meaning no fields are excluded). The resulting SearchHits will contain documents with only the specified fields.