perf(db): Added indexes

src/models/entities/Runner.ts

@@ -1,5 +1,5 @@
 import { IsInt, IsNotEmpty, IsOptional, IsString } from "class-validator";
-import { ChildEntity, Column, ManyToOne, OneToMany } from "typeorm";
+import { ChildEntity, Column, Index, ManyToOne, OneToMany } from "typeorm";
 import { ResponseRunner } from '../responses/ResponseRunner';
 import { DistanceDonation } from "./DistanceDonation";
 import { Participant } from "./Participant";
@@ -11,8 +11,9 @@ import { Scan } from "./Scan";
  * Defines the runner entity.
  * Runners differ from participants in being able to actually accumulate a ran distance through scans.
  * Runner's get organized in groups.
-*/
+ */
 @ChildEntity()
+@Index(['group'])
 export class Runner extends Participant {
   /**
    * The runner's associated group.