Elasticsearch: Fix using of datetime format for time field (#64676)

* Elasticsearch: Fix using of datetime format for time field

* Use convertFieldType to convert time field for better performance

public/app/plugins/datasource/elasticsearch/ElasticResponse.test.ts

@@ -1301,6 +1301,7 @@ describe('ElasticResponse', () => {
           refId: 'A',
           metrics: [{ type: 'raw_data', id: '1' }],
           bucketAggs: [],
+          timeField: '@timestamp',
         },
       ];
 
@@ -1317,7 +1318,7 @@ describe('ElasticResponse', () => {
                   _id: '1',
                   _type: '_doc',
                   _index: 'index',
-                  _source: { sourceProp: 'asd' },
+                  _source: { sourceProp: 'asd', '@timestamp': '2019-01-01T00:00:00Z' },
                 },
               ],
             },
@@ -1333,6 +1334,12 @@ describe('ElasticResponse', () => {
         expect(field.config.filterable).toBe(true);
       }
     });
+
+    it('should have time field values in DateTime format', () => {
+      const timeField = result.data[0].fields.find((field) => field.name === '@timestamp');
+      expect(timeField).toBeDefined();
+      expect(timeField?.values.get(0)).toBe(1546300800000);
+    });
   });
 
   describe('simple logs query and count', () => {

public/app/plugins/datasource/elasticsearch/ElasticResponse.ts

@@ -8,6 +8,7 @@ import {
   MutableDataFrame,
   PreferredVisualisationType,
 } from '@grafana/data';
+import { convertFieldType } from '@grafana/data/src/transformations/transformers/convertFieldType';
 import TableModel from 'app/core/TableModel';
 import flatten from 'app/core/utils/flatten';
 
@@ -601,6 +602,14 @@ export class ElasticResponse {
       }
     }
 
+    for (let frame of dataFrame) {
+      for (let field of frame.fields) {
+        if (field.type === FieldType.time && typeof field.values.get(0) !== 'number') {
+          field.values = convertFieldType(field, { destinationType: FieldType.time }).values;
+        }
+      }
+    }
+
     return { data: dataFrame };
   }