Impala Miscellaneous Functions
Impala supports the following utility functions that do not operate on a particular column or data type:
- current_database()
- Purpose: Returns the database that the session is currently using, either default if no database has been selected, or
whatever database the session switched to through a USE statement or the impalad-d option.
Return type: string
- effective_user()
- Purpose: Typically returns the same value as user(), except if delegation is enabled, in which case it returns the ID of
the delegated user.
Return type: string
Added in: CDH 5.4.5
- pid()
- Purpose: Returns the process ID of the impalad daemon that the session is connected to. You can use it during
low-level debugging, to issue Linux commands that trace, show the arguments, and so on the impalad process.
Return type: int
- user()
- Purpose: Returns the username of the Linux user who is connected to the impalad daemon. Typically called a single
time, in a query without any FROM clause, to understand how authorization settings apply in a security context; once you know the logged-in user name, you can check
which groups that user belongs to, and from the list of groups you can check which roles are available to those groups through the authorization policy file.
In Impala 2.0 and later, user() returns the full Kerberos principal string, such as user@example.com, in a Kerberized environment.
When delegation is enabled, consider calling the effective_user() function instead.
Return type: string
- version()
- Purpose: Returns information such as the precise version number and build date for the impalad daemon that you are
currently connected to. Typically used to confirm that you are connected to the expected level of Impala to use a particular feature, or to connect to several nodes and confirm they are all running
the same level of impalad.
Return type: string (with one or more embedded newlines)