azurerm_postgresql_flexible_server: downgrading version forces a new resource to be created (#28559)

Author: wuxu92

internal/services/postgres/postgresql_flexible_server_resource.go

@@ -351,31 +351,17 @@ func resourcePostgresqlFlexibleServer() *pluginsdk.Resource {
 		},
 
 		CustomizeDiff: pluginsdk.CustomDiffWithAll(func(ctx context.Context, d *pluginsdk.ResourceDiff, v interface{}) error {
-			createModeVal := d.Get("create_mode").(string)
-
-			if createModeVal == string(servers.CreateModeUpdate) {
+			if d.HasChange("version") {
 				oldVersionVal, newVersionVal := d.GetChange("version")
+				// `version` value has been validated already, ignore the parse errors is safe
+				oldVersion, _ := strconv.ParseInt(oldVersionVal.(string), 10, 32)
+				newVersion, _ := strconv.ParseInt(newVersionVal.(string), 10, 32)
 
-				if oldVersionVal != "" && newVersionVal != "" {
-					oldVersion, err := strconv.ParseInt(oldVersionVal.(string), 10, 32)
-					if err != nil {
-						return err
-					}
-
-					newVersion, err := strconv.ParseInt(newVersionVal.(string), 10, 32)
-					if err != nil {
-						return err
-					}
-
-					if oldVersion < newVersion {
-						return nil
-					}
+				if oldVersion > newVersion {
+					d.ForceNew("version")
 				}
+				return nil
 			}
-
-			d.ForceNew("create_mode")
-			d.ForceNew("version")
-
 			return nil
 		}, func(ctx context.Context, diff *pluginsdk.ResourceDiff, v interface{}) error {
 			oldLoginName, _ := diff.GetChange("administrator_login")

internal/services/postgres/postgresql_flexible_server_resource_test.go

@@ -178,6 +178,40 @@ func TestAccPostgresqlFlexibleServer_updateSku(t *testing.T) {
 	})
 }
 
+func TestAccPostgresqlFlexibleServer_updateVersion(t *testing.T) {
+	data := acceptance.BuildTestData(t, "azurerm_postgresql_flexible_server", "test")
+	r := PostgresqlFlexibleServerResource{}
+	data.ResourceTest(t, r, []acceptance.TestStep{
+		{
+			Config: r.withVersion(data, 12, ""),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		data.ImportStep("administrator_password", "create_mode"),
+		{
+			Config: r.withVersion(data, 13, ""),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		{
+			Config: r.withVersion(data, 13, "Update"),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		data.ImportStep("administrator_password", "create_mode"),
+		{
+			Config: r.withVersion(data, 14, "Default"),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		data.ImportStep("administrator_password", "create_mode"),
+	})
+}
+
 func TestAccPostgresqlFlexibleServer_geoRestore(t *testing.T) {
 	data := acceptance.BuildTestData(t, "azurerm_postgresql_flexible_server", "test")
 	r := PostgresqlFlexibleServerResource{}
@@ -772,6 +806,29 @@ resource "azurerm_postgresql_flexible_server" "test" {
 `, r.template(data), data.RandomInteger)
 }
 
+func (r PostgresqlFlexibleServerResource) withVersion(data acceptance.TestData, versionNum int, creatMode string) string {
+	createModeProp := ""
+	if creatMode != "" {
+		createModeProp = fmt.Sprintf("create_mode = \"%s\"", creatMode)
+	}
+
+	return fmt.Sprintf(`
+%s
+
+resource "azurerm_postgresql_flexible_server" "test" {
+  name                   = "acctest-fs-%d"
+  resource_group_name    = azurerm_resource_group.test.name
+  location               = azurerm_resource_group.test.location
+  administrator_login    = "adminTerraform"
+  administrator_password = "QAZwsx123"
+  version                = "%d"
+  %s
+  sku_name = "GP_Standard_D2s_v3"
+  zone     = "2"
+}
+`, r.template(data), data.RandomInteger, versionNum, createModeProp)
+}
+
 func (r PostgresqlFlexibleServerResource) geoRestoreSource(data acceptance.TestData) string {
 	return fmt.Sprintf(`
 provider "azurerm" {

website/docs/r/postgresql_flexible_server.html.markdown

@@ -113,11 +113,7 @@ The following arguments are supported:
 
 * `geo_redundant_backup_enabled` - (Optional) Is Geo-Redundant backup enabled on the PostgreSQL Flexible Server. Defaults to `false`. Changing this forces a new PostgreSQL Flexible Server to be created.
 
-* `create_mode` - (Optional) The creation mode which can be used to restore or replicate existing servers. Possible values are `Default`, `GeoRestore`, `PointInTimeRestore`, `Replica` and `Update`. Changing this forces a new PostgreSQL Flexible Server to be created.
-
--> **Note:** `create_mode` cannot be changed once it's set since it's a parameter at creation.
-
--> **Note:** While creating the resource, `create_mode` cannot be set to `Update`.
+* `create_mode` - (Optional) The creation mode which can be used to restore or replicate existing servers. Possible values are `Default`, `GeoRestore`, `PointInTimeRestore`, `Replica` and `Update`.
 
 * `delegated_subnet_id` - (Optional) The ID of the virtual network subnet to create the PostgreSQL Flexible Server. The provided subnet should not have any other resource deployed in it and this subnet will be delegated to the PostgreSQL Flexible Server, if not already delegated. Changing this forces a new PostgreSQL Flexible Server to be created.
 
@@ -161,7 +157,9 @@ The following arguments are supported:
 
 * `version` - (Optional) The version of PostgreSQL Flexible Server to use. Possible values are `11`,`12`, `13`, `14`, `15` and `16`. Required when `create_mode` is `Default`.
 
--> **Note:** When `create_mode` is `Update`, upgrading version wouldn't force a new resource to be created.
+-> **Note:** Downgrading `version` isn't supported and will force a new PostgreSQL Flexible Server to be created.
+
+-> **Note:** In-place version updates are irreversible and may cause downtime for the PostgreSQL Flexible Server, determined by the size of the instance.
 
 * `zone` - (Optional) Specifies the Availability Zone in which the PostgreSQL Flexible Server should be located.