add a toggle for this option

docs/reference/operator_parameters.md

@@ -131,6 +131,10 @@ Those are top-level keys, containing both leaf keys and groups.
   container, change the [operator deployment manually](../../manifests/postgres-operator.yaml#L20).
   The default is `false`.
 
+* **should_delete_unused_pvc**
+  Tells the operator to delete persistent volume claims of no longer running pods. That removes respective persistent volumes because operator configures them with the 'Delete' reclaim policy. Note operator deletes unused PVCs for clusters created both before and after this option is turned on. Deletion is not guaranteed: When it fails, operator retries at next Sync() event.
+  The default is `false`.
+
 ## Postgres users
 
 Parameters describing Postgres users. In a CRD-configuration, they are grouped

manifests/configmap.yaml

@@ -88,5 +88,6 @@ data:
   # teams_api_url: http://fake-teams-api.default.svc.cluster.local
   # toleration: ""
   # wal_s3_bucket: ""
+  # should_delete_unused_pvc: "false" 
   watched_namespace: "*"  # listen to all namespaces
   workers: "4"

pkg/cluster/cluster.go

@@ -634,8 +634,7 @@ func (c *Cluster) Update(oldSpec, newSpec *acidv1.Postgresql) error {
 		}
 	}()
 
-	// delete persistent volume claim after scale down
-	if oldSpec.Spec.NumberOfInstances > newSpec.Spec.NumberOfInstances {
+	if c.OpConfig.ShouldDeleteUnusedPVC && oldSpec.Spec.NumberOfInstances > newSpec.Spec.NumberOfInstances {
 		c.logger.Debug("deleting pvc of shut down pods")
 
 		for i := oldSpec.Spec.NumberOfInstances - 1; i >= newSpec.Spec.NumberOfInstances; i-- {

pkg/cluster/sync.go

@@ -111,8 +111,9 @@ func (c *Cluster) Sync(newSpec *acidv1.Postgresql) error {
 
 	// remove unused PVCs in case deleting them during scale down failed; see Update()
 	// the last pvc stays until the cluster is explicitly deleted as opposed to being scaled down to 0 pods
-	if c.getNumberOfInstances(&c.Spec) > 0 {
+	if c.OpConfig.ShouldDeleteUnusedPVC && c.getNumberOfInstances(&c.Spec) > 0 {
 
+		// XXX that also deletes PVC of pods shut down before this change is deployed
 		for i := c.getNumberOfInstances(&c.Spec); ; i++ {
 			podIndex := strconv.Itoa(int(i))
 			pvcName := "pgdata-" + c.Name + "-" + podIndex

pkg/util/config/config.go

@@ -137,6 +137,7 @@ type Config struct {
 	ProtectedRoles            []string          `name:"protected_role_names" default:"admin"`
 	PostgresSuperuserTeams    []string          `name:"postgres_superuser_teams" default:""`
 	SetMemoryRequestToLimit   bool              `name:"set_memory_request_to_limit" default:"false"`
+	ShouldDeleteUnusedPVC     bool              `name:"should_delete_unused_pvc" default:"false"`
 }
 
 // MustMarshal marshals the config or panics