OSS provides the hierarchical namespace feature for you to manage objects in a multi-level hierarchical structure based on directories. This feature allows you to rename a directory or an object by performing a single atomic operation. This way, you do not need to list or process all objects whose names contain the same prefix. Traditionally, OSS uses a flat namespace to store objects in buckets and simulates directories by using objects whose names end with a forward slash (/). Compared with this method, the hierarchical namespace feature greatly improves the performance of directory management.
- Atomic operations on directories
If a bucket uses a flat namespace in which real directories are not supported, applications may need to process millions of objects to complete a task at the directory level. In contrast, if the hierarchical namespace feature is enabled for a bucket, applications can update a parent directory in a single atomic operation to complete multiple directory-level tasks at the same time.
- Optimized performance
Compared with a flat namespace, a hierarchical namespace eliminates the need to replicate or convert data before the data is analyzed. This improves the performance of directory management. The hierarchical namespace feature is especially important for big data analytics frameworks. For example, Hive or Spark writes output results to a temporary directory during task execution and renames the directory after the task is complete. In a flat hierarchical namespace, the time that is consumed to rename the directory is usually longer than the time that is consumed to perform the task.
You can enable the hierarchical namespace feature for a bucket only when you create the bucket. The hierarchical namespace feature cannot be disabled after it is enabled for a bucket. For more information about how to enable the hierarchical namespace feature, see Create buckets.
The following table describes the methods that you can use to create, rename, or delete directories in a bucket for which the hierarchical namespace feature is enabled.
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- Supported region
The hierarchical namespace feature is available only in the following regions: Australia (Sydney), US (Silicon Valley), Japan (Tokyo), India (Mumbai), UK (London), and Malaysia (Kuala Lumpur).
- Create a directory
A directory name cannot contain consecutive forward slashes (/).
Data cannot be written to directories. The Content-Length of a directory can be set only to 0.
The Content-Type of a directory can be set only to
- Rename a directory or object
The name of a renamed directory or object cannot be the same as the name of an existing directory or object in the same bucket.
The parent directory that is included in the name of a renamed directory or object must exist. For example, if you rename a directory
destfolder/examplefolder/test, the parent directory
destfolder/examplefoldermust exist in the bucket.
- Delete a directory
- Recursive delete
Recursive delete is used to delete a directory and all objects and subdirectories within the directory. To use recursive delete, you must have the DeleteObject permission on the directory and all objects and subdirectories within the directory that you want to delete.
For example, if you want to use recursive delete to delete the dest/testfolder directory and the objects in the directory, you must have the DeleteObject permission on
dest/testfolder/*.Notice If a concurrent request is sent to write data to a directory when you use recursive delete to delete the directory, the directory may fail to be deleted.
- Non-recursive delete
Non-recursive delete is used to delete empty directories. To use non-recursive delete, you must have the DeleteObject permission on the directory that you want to delete.
- Recursive delete
The following table describes the features that are not supported by buckets for which the hierarchical namespace feature is enabled.