Merge branch 'reduce-query-overhead-for-mr-count' into 'master'

Do not load MR records when requesting counts

See merge request gitlab-org/gitlab!40339

ee/app/assets/javascripts/analytics/merge_request_analytics/graphql/throughput_chart_query_builder.js

@@ -19,7 +19,9 @@ export default (startDate = null, endDate = null) => {
   const computedMonthData = monthData.map(value => {
     const { year, month, mergedAfter, mergedBefore } = value;
 
-    return `${month}_${year}: mergeRequests(mergedBefore: "${mergedBefore}", mergedAfter: "${mergedAfter}") { count }`;
+    // first: 0 is an optimization which makes sure we don't load merge request objects into memory (backend).
+    // Currently when requesting counts we also load the first 100 records (preloader problem).
+    return `${month}_${year}: mergeRequests(first: 0, mergedBefore: "${mergedBefore}", mergedAfter: "${mergedAfter}") { count }`;
   });
 
   return gql`

ee/spec/frontend/analytics/merge_request_analytics/mock_data.js

@@ -33,13 +33,13 @@ export const expectedMonthData = [
 
 export const throughputChartQuery = `query ($fullPath: ID!) {
   throughputChartData: project(fullPath: $fullPath) {
-    May_2020: mergeRequests(mergedBefore: "2020-06-01", mergedAfter: "2020-05-01") {
+    May_2020: mergeRequests(first: 0, mergedBefore: "2020-06-01", mergedAfter: "2020-05-01") {
       count
     }
-    Jun_2020: mergeRequests(mergedBefore: "2020-07-01", mergedAfter: "2020-06-01") {
+    Jun_2020: mergeRequests(first: 0, mergedBefore: "2020-07-01", mergedAfter: "2020-06-01") {
       count
     }
-    Jul_2020: mergeRequests(mergedBefore: "2020-08-01", mergedAfter: "2020-07-01") {
+    Jul_2020: mergeRequests(first: 0, mergedBefore: "2020-08-01", mergedAfter: "2020-07-01") {
       count
     }
   }