XATTR and Virtual XATTR
- concept
Extended Attributes (XATTR) are metadata that can be provided on a per-application basis.
Using Extended Attributes
The SDK supports extended attributes by means of extensions to the Sub-Document API: so that extended attributes can be defined, searched for, edited, removed, and more.
In order to specify that a subdocument operation should be performed on an extended rather than a regular attribute, an xattr
flag should be set to true
, by the calling application.
For detailed information on the Subdocument API, see Subdocument Operations, and the accompanying practical doc.
For more information, see Extended Attributes.
The maximum content size for a document stored in Couchbase Server is 20MB. XATTRs — including Virtual XATTRs — will reduce the space available for the remainder of the document. |
Virtual Extended Attributes
Virtual extended attributes consist of metadata on an individual document: this can be retrieved by specifying $document
as a search-path — see below.
See the Virtual XATTR Section for more information on the metadata that they expose.
These attributes are generated on-demand to expose storage-level document metadata, such as expiry to expose document expiration. For expiry using Virtual XATTR, use the following: