Add explicit format parameter to docvalue_fields requests

src/ui/public/agg_types/__tests__/metrics/top_hit.js

@@ -90,7 +90,7 @@ describe('Top hit metric', function () {
   it('requests both source and docvalues_fields for non-text aggregatable fields', function () {
     init({ field: 'bytes' });
     expect(aggDsl.top_hits._source).to.be('bytes');
-    expect(aggDsl.top_hits.docvalue_fields).to.eql([ 'bytes' ]);
+    expect(aggDsl.top_hits.docvalue_fields).to.eql([ { field: 'bytes', format: 'use_field_mapping' } ]);
   });
 
   it('requests just source for aggregatable text fields', function () {

src/ui/public/agg_types/metrics/top_hit.js

@@ -62,7 +62,7 @@ export const topHitMetricAgg = new MetricAggType({
           };
         } else {
           if (field.readFromDocValues) {
-            output.params.docvalue_fields = [ field.name ];
+            output.params.docvalue_fields = [ { field: field.name, format: 'use_field_mapping' } ];
           }
           output.params._source = field.name === '_source' ? true : field.name;
         }

src/ui/public/index_patterns/__tests__/_get_computed_fields.js

@@ -43,8 +43,19 @@ describe('get computed fields', function () {
   });
 
   it('should request date fields as docvalue_fields', function () {
-    expect(fn().docvalueFields).to.contain('@timestamp');
-    expect(fn().docvalueFields).to.not.contain('bytes');
+    const docvalueFields = fn().docvalueFields;
+    const docvalueFieldNames = docvalueFields.map(field => field.field);
+
+    expect(docvalueFields).to.have.length(3);
+    expect(docvalueFieldNames).to.contain('@timestamp');
+    expect(docvalueFieldNames).to.contain('time');
+    expect(docvalueFieldNames).to.contain('utc_time');
+  });
+
+  it('should request date field doc values in epoch_millis format', function () {
+    const docvalueFields = fn().docvalueFields;
+    const timestampField = docvalueFields.find((field) => field.field === '@timestamp');
+    expect(timestampField).to.have.property('format', 'epoch_millis');
   });
 
   it('should not request scripted date fields as docvalue_fields', function () {

src/ui/public/index_patterns/_get_computed_fields.js

@@ -25,7 +25,13 @@ export function getComputedFields() {
   const scriptFields = {};
   let docvalueFields = [];
 
-  docvalueFields = _.map(_.reject(self.fields.byType.date, 'scripted'), 'name');
+  docvalueFields = _.reject(self.fields.byType.date, 'scripted')
+    .map((dateField) => {
+      return {
+        field: dateField.name,
+        format: 'epoch_millis',
+      };
+    });
 
   _.each(self.getScriptedFields(), function (field) {
     scriptFields[field.name] = {