Variables: Do not update variable from url when value is the same (#23220)

(cherry picked from commit 49d2910e)

public/app/features/templating/variable_srv.ts

@@ -330,9 +330,12 @@ export class VariableSrv {
     for (const v of this.variables) {
       const key = `var-${v.name}`;
       if (vars.hasOwnProperty(key)) {
-        update.push(v.setValueFromUrl(vars[key]));
+        if (this.isVariableUrlValueDifferentFromCurrent(v, vars[key])) {
+          update.push(v.setValueFromUrl(vars[key]));
+        }
       }
     }
+
     if (update.length) {
       Promise.all(update).then(() => {
         this.dashboard.templateVariableValueUpdated();
@@ -341,6 +344,11 @@ export class VariableSrv {
     }
   }
 
+  isVariableUrlValueDifferentFromCurrent(variable: any, urlValue: any) {
+    // lodash _.isEqual handles array of value equality checks as well
+    return !_.isEqual(variable.current.value, urlValue);
+  }
+
   updateUrlParamsWithCurrentVariables() {
     // update url
     const params = this.$location.search();