Impala databases

Each database defines a separate namespace. Creating a database is a lightweight operation. There are minimal database-specific properties to configure, such as LOCATION and COMMENT.

You can change the owner of a database with the ALTER DATABASE statement.

Typically, you create a separate database for each project or application, to avoid naming conflicts between tables and to make clear which tables are related to each other.

The USE statement lets you switch between databases. Unqualified references to tables, views, and functions refer to objects within the current database. You can also refer to objects in other databases by using qualified names of the form dbname.object_name.

Each database is physically represented by a directory in HDFS. When you do not specify a LOCATION attribute, the directory is located in the Impala data directory with the associated tables managed by Impala. When you do specify a LOCATION attribute, any read and write operations for tables in that database are relative to the specified HDFS directory.

• default

  By default, you use the default database when you connect to Impala. Tables created in the default database are physically located at one level higher in HDFS than all the user-created databases.

• _impala_builtins

  All Impala built-in functions reside in this database.