Add explicit format parameter to docvalue_fields requests (#22771)

Fixes #22484

Elasticsearch 6.4 added an optional `format` parameter for doc_value
fields. In 6.x if the param is not included it defaults to returning
the same values we see in scripted fields. In 7.0 this is changing to
use the mapping configured format by default. In kibana we want our date
values in ISO format, so this PR future proofs us for 7.0. It also eliminates
deprecation warnings ES is returning due to the missing param, which is
currently spamming some users.

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/courier/search_source/search_source.js

@@ -583,7 +583,9 @@ export function SearchSourceProvider(Promise, Private, config) {
           if (flatData.body._source) {
             // exclude source fields for this index pattern specified by the user
             const filter = fieldWildcardFilter(flatData.body._source.excludes);
-            flatData.body.docvalue_fields = flatData.body.docvalue_fields.filter(filter);
+            flatData.body.docvalue_fields = flatData.body.docvalue_fields.filter(
+              docvalueField => filter(docvalueField.field)
+            );
           }
 
           // if we only want to search for certain fields

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 date_time format', function () {
+    const docvalueFields = fn().docvalueFields;
+    const timestampField = docvalueFields.find((field) => field.field === '@timestamp');
+    expect(timestampField).to.have.property('format', 'date_time');
   });
 
   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: 'date_time',
+      };
+    });
 
   _.each(self.getScriptedFields(), function (field) {
     scriptFields[field.name] = {