prometheus nested query support

public/app/plugins/datasource/prometheus/datasource.ts

@@ -155,6 +155,7 @@ export class PrometheusDatasource {
 
     // Only replace vars in expression after having (possibly) updated interval vars
     query.expr = this.templateSrv.replace(target.expr, scopedVars, this.interpolateQueryExpr);
+    query.expr = this.replaceNestedQuery(query.expr, options);
     query.requestId = options.panelId + target.refId;
     return query;
   }
@@ -269,6 +270,13 @@ export class PrometheusDatasource {
     });
   }
 
+  replaceNestedQuery(query, options) {
+    return query.replace(/\#([A-Z])/g, (match, g1) => {
+      let replaceTarget = options.targets.find((t) => { return t.refId === g1; });
+      return replaceTarget ? replaceTarget.expr : match;
+    });
+  }
+
   transformMetricData(md, options, start, end, step) {
     var dps = [],
       metricLabel = null;

public/app/plugins/datasource/prometheus/specs/datasource_specs.ts

@@ -590,4 +590,19 @@ describe('PrometheusDatasource', function() {
       expect(query.scopedVars.__interval_ms.value).to.be(5 * 1000);
     });
   });
+  describe('The nested query', function() {
+    it('should generate correct query', function() {
+      let query = 'sum(rate(#A[1m]))';
+      let options = {
+        targets: [
+          {
+            refId: 'A',
+            expr: 'http_requests_total'
+          }
+        ]
+      };
+      let result = ctx.ds.replaceNestedQuery(query, options);
+      expect(result).to.be('sum(rate(http_requests_total[1m]))');
+    });
+  });
 });