box.space._vuser

box.space._vuser

_vuser is a system space that represents a virtual view. The structure of its tuples is identical to that of _user, but permissions for certain tuples are limited in accordance with user privileges. _vuser contains only those tuples that are accessible to the current user. See Access control for details about user privileges.

If the user has the full set of privileges (like ‘admin’), the contents of _vuser match the contents of _user. If the user has limited access, _vuser contains only tuples accessible to this user.

To see how _vuser works, connect to a Tarantool database remotely via net.box and select all tuples from the _user space, both when the ‘guest’ user is and is not allowed to read from the database.

First, start Tarantool and grant the ‘guest’ user with read, write and execute privileges:

tarantool> box.cfg{listen = 3301}
---
...
tarantool> box.schema.user.grant('guest', 'read,write,execute', 'universe')
---
...

Switch to the other terminal, connect to the Tarantool instance and select all tuples from the _user space:

tarantool> conn = require('net.box').connect(3301)
---
...
tarantool> conn.space._user:select{}
---
- - [0, 1, 'guest', 'user', {}]
  - [1, 1, 'admin', 'user', {}]
  - [2, 1, 'public', 'role', {}]
  - [3, 1, 'replication', 'role', {}]
  - [31, 1, 'super', 'role', {}]
...

This result contains the same set of users as if you made the request from your Tarantool instance as ‘admin’.

Switch to the first terminal and revoke the read privileges from the ‘guest’ user:

tarantool> box.schema.user.revoke('guest', 'read', 'universe')
---
...

Switch to the other terminal, stop the session (to stop tarantool type Ctrl+C or Ctrl+D), start again, connect again, and repeat the conn.space._user:select{} request. The access is denied:

tarantool> conn.space._user:select{}
---
- error: Read access to space '_user' is denied for user 'guest'
...

However, if you select from _vuser instead, the users’ data available for the ‘guest’ user is displayed:

tarantool> conn.space._vuser:select{}
---
- - [0, 1, 'guest', 'user', {}]
...

Note

• _vuser is a system view, so it allows only read requests.
• While the _user space requires proper access privileges, any user can always read from _vuser.