fix variable interpolation

public/app/plugins/datasource/postgres/postgres_query.ts

@@ -239,6 +239,9 @@ export default class PostgresQuery {
 
     query += ' ORDER BY time';
 
+    if (interpolate) {
+      query = this.templateSrv.replace(query, this.scopedVars, this.interpolateQueryStr);
+    }
     return query;
   }
 

public/app/plugins/datasource/postgres/query_ctrl.ts

@@ -207,7 +207,7 @@ export class PostgresQueryCtrl extends QueryCtrl {
           segments.unshift(
             this.uiSegmentSrv.newSegment({
               type: 'template',
-              value: '/^$' + variable.name + '$/',
+              value: '$' + variable.name,
               expandable: true,
             })
           );