Common usecase for updating and re-creating the index is to stop the server and manually remove indexes for workspaces requiring it. When server will be started, missing indexes are automatically recovered by re-indexing. JCR Supports direct RDBMS re-indexing, that usually is faster than ordinary and can be configured via QueryHandler parameter "rdbms-reindexing" set to "true" (for more information please refer to "Query-handler configuration overview"). New feature to introduce is asynchronous indexing on startup. Usually startup is blocked until process is finished. Block can take any period of time, depending on amount of data persisted in repositories. But this can be resolved by using an asynchronous approaches of startup indexation. Saying briefly, it performs all operations with index in background, without blocking the repository. This is controlled by the value of "async-reindexing" parameter in QueryHandler configuration. With asynchronous indexation active, JCR starts with no active indexes present. Queries on JCR still can be executed without exceptions, but no results will be returned until index creation completed. Checking index state is possible via QueryManagerImpl:

boolean online = ((QueryManagerImpl)Workspace.getQueryManager()).getQueryHandeler().isOnline();

"OFFLINE" state means that index is currently re-creating. When state changed, corresponding log event is printed. From the start of background task index is switched to "OFFLINE", with following log event :

[INFO] Setting index OFFLINE (repository/production[system]).

When process finished, two events are logged :

[INFO] Created initial index for 143018 nodes (repository/production[system]).
[INFO] Setting index ONLINE (repository/production[system]).

Those two log lines indicates the end of process for workspace given in brackets. Calling isOnline() as mentioned above, will also return true.