Remove collation from update request and make collation non-updatable (#6298) (#4505)

Signed-off-by: Modular Magician <[email protected]>

Author: modular-magician

.changelog/6298.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+sql: fixed an issue in `google_sql_database_instance` where updates would fail because of the `collation` field
+```

google-beta/resource_sql_database_instance.go

@@ -267,6 +267,7 @@ is set to true.`,
 						"collation": {
 							Type:        schema.TypeString,
 							Optional:    true,
+							ForceNew:    true,
 							Description: `The name of server instance collation.`,
 						},
 						"database_flags": {
@@ -1305,6 +1306,9 @@ func resourceSqlDatabaseInstanceUpdate(d *schema.ResourceData, meta interface{})
 		Settings: expandSqlDatabaseInstanceSettings(d.Get("settings").([]interface{})),
 	}
 
+	// Collation cannot be included in the update request
+	instance.Settings.Collation = ""
+
 	// Lock on the master_instance_name just in case updating any replica
 	// settings causes operations on the master.
 	if v, ok := d.GetOk("master_instance_name"); ok {

google-beta/resource_sql_database_instance_test.go

@@ -222,6 +222,16 @@ func TestAccSqlDatabaseInstance_basicMSSQL(t *testing.T) {
 				ImportStateVerify:       true,
 				ImportStateVerifyIgnore: []string{"root_password", "deletion_protection"},
 			},
+			{
+				Config: fmt.Sprintf(
+					testGoogleSqlDatabaseInstance_update_mssql, databaseName, rootPassword),
+			},
+			{
+				ResourceName:            "google_sql_database_instance.instance",
+				ImportState:             true,
+				ImportStateVerify:       true,
+				ImportStateVerifyIgnore: []string{"root_password", "deletion_protection"},
+			},
 		},
 	})
 }
@@ -1221,6 +1231,23 @@ resource "google_sql_database_instance" "instance" {
 }
 `
 
+var testGoogleSqlDatabaseInstance_update_mssql = `
+resource "google_sql_database_instance" "instance" {
+  name                = "%s"
+  database_version    = "SQLSERVER_2019_STANDARD"
+  root_password       = "%s"
+  deletion_protection = false
+  settings {
+    tier = "db-custom-1-3840"
+    collation = "Polish_CI_AS"
+    ip_configuration {
+      ipv4_enabled = true
+      require_ssl = true
+    }
+  }
+}
+`
+
 func testGoogleSqlDatabaseInstance_ActiveDirectoryConfig(databaseName, networkName, addressRangeName, rootPassword, adDomainName string) string {
 	return fmt.Sprintf(`
 data "google_compute_network" "servicenet" {