azurerm_eventhub - remove ForceNew and check partition_count is n…

…ot decreased (hashicorp#23499)

* remove ForceNew and check partition_count is not decreased

* update doc

internal/services/eventhub/eventhub_resource.go

@@ -63,7 +63,6 @@ func resourceEventHub() *pluginsdk.Resource {
 			"partition_count": {
 				Type:         pluginsdk.TypeInt,
 				Required:     true,
-				ForceNew:     true,
 				ValidateFunc: validate.ValidateEventHubPartitionCount,
 			},
 
@@ -222,6 +221,12 @@ func resourceEventHubUpdate(d *pluginsdk.ResourceData, meta interface{}) error {
 	id := eventhubs.NewEventhubID(subscriptionId, d.Get("resource_group_name").(string), d.Get("namespace_name").(string), d.Get("name").(string))
 
 	if d.HasChange("partition_count") {
+
+		o, n := d.GetChange("partition_count")
+		if o.(int) > n.(int) {
+			return fmt.Errorf("`partition_count` cannot be decreased")
+		}
+
 		client := meta.(*clients.Client).Eventhub.NamespacesClient
 		namespaceId := namespaces.NewNamespaceID(subscriptionId, id.ResourceGroupName, id.NamespaceName)
 		resp, err := client.Get(ctx, namespaceId)

website/docs/r/eventhub.html.markdown

@@ -49,9 +49,9 @@ The following arguments are supported:
 
 * `resource_group_name` - (Required) The name of the resource group in which the EventHub's parent Namespace exists. Changing this forces a new resource to be created.
 
-* `partition_count` - (Required) Specifies the current number of shards on the Event Hub. Changing this will force-recreate the resource.
+* `partition_count` - (Required) Specifies the current number of shards on the Event Hub.
 
-~> **Note:** `partition_count` cannot be changed unless Eventhub Namespace SKU is `Premium`.
+~> **Note:** `partition_count` cannot be changed unless Eventhub Namespace SKU is `Premium` and cannot be decreased.
 
 ~> **Note:** When using a dedicated Event Hubs cluster, maximum value of `partition_count` is 1024. When using a shared parent EventHub Namespace, maximum value is 32.