use iterator to reduce cache in migration

3 jobs for improve-source in 3 minutes and 29 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Build
passed #128526
k8s
build-backend

00:02:24

passed #128527
k8s
build-frontend

00:01:22

 
  Test
passed #128528
test-backend

00:01:04