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

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.

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)