Impala databases
Databases are logical containers for a group of tables, and 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 thedefault
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.