9d2f8043_Troubleshooting_Impala__Recommendation
[Symptom] Attempts to complete Impala tasks such as executing INSERT-SELECT actions fail. The Impala logs include notes that files could not be opened due to permission denied. [Explanation] This can be the result of permissions issues. For example, you could use the Hive shell as the hive user to create a table. After creating this table, you could attempt to complete some action, such as an INSERT-SELECT on the table. Because the table was created using one user and the INSERT-SELECT is attempted by another, this action may fail due to permissions issues. [Recommendation] 
In general, ensure the Impala user has sufficient permissions. In the preceding example, ensure the Impala user has sufficient permissions to the table that the Hive user created.
Troubleshooting Impala