There are two functions to get details about the user who is connected to Impala Daemon. The first is USER() and the second is EFFECTIVE USER(). Both functions show the same username when you execute in ClouderaVM, but there is a distinction between them.
Let’s see what USER() function displays:
User() function returns the username of the Linux user who is connected to the impalad daemon.
When users submit Impala queries through a separate application, such as Hue or a business intelligence tool, typically all requests are treated as coming from the same user. In Impala 1.2 and higher, Impala supports “delegation” where users whose names you specify can delegate the execution of a query to another user. The query runs with the privileges of the delegated user, not the original authenticated user. It is recommended to use effective_user() when delegation is enabled.
Big Data and SQL 
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