[data.search.aggs] Remove use_field_mapping from top hits agg (#71168)

src/plugins/data/public/search/aggs/metrics/top_hit.test.ts

@@ -111,9 +111,7 @@ describe('Top hit metric', () => {
  it('requests both source and docvalues_fields for non-text aggregatable fields', () => {
  init({ fieldName: 'bytes', readFromDocValues: true });
  expect(aggDsl.top_hits._source).toBe('bytes');
- expect(aggDsl.top_hits.docvalue_fields).toEqual([
- { field: 'bytes', format: 'use_field_mapping' },
- ]);
+ expect(aggDsl.top_hits.docvalue_fields).toEqual([{ field: 'bytes' }]);
  });
 
  it('requests both source and docvalues_fields for date aggregatable fields', () => {

src/plugins/data/public/search/aggs/metrics/top_hit.ts

@@ -88,12 +88,15 @@ export const getTopHitMetricAgg = () => {
  };
  } else {
  if (field.readFromDocValues) {
- // always format date fields as date_time to avoid
- // displaying unformatted dates like epoch_millis
- // or other not-accepted momentjs formats
- const format =
- field.type === KBN_FIELD_TYPES.DATE ? 'date_time' : 'use_field_mapping';
- output.params.docvalue_fields = [{ field: field.name, format }];
+ output.params.docvalue_fields = [
+ {
+ field: field.name,
+ // always format date fields as date_time to avoid
+ // displaying unformatted dates like epoch_millis
+ // or other not-accepted momentjs formats
+ ...(field.type === KBN_FIELD_TYPES.DATE && { format: 'date_time' }),
+ },
+ ];
  }
  output.params._source = field.name === '_source' ? true : field.name;
  }