ALTER DATABASE¶
Function¶
Modifies the attributes of a database, including the database name, owner, maximum number of connections, and object isolation attributes.
Important Notes¶
Only the owner of a database or a system administrator has the permission to run the ALTER DATABASE statement. Users other than system administrators may have the following permission constraints depending on the attributes to be modified:
To modify the database name, you must have the CREATEDB permission.
To modify a database owner, you must be a database owner and a member of the new owner, and have the CREATEDB permission.
To change the default tablespace, you must be a database owner or a system administrator, and must have the CREATE permission on the new tablespace. This statement physically migrates tables and indexes in a default tablespace to a new tablespace. Note that tables and indexes outside the default tablespace are not affected.
Only a database owner or a system administrator can modify GUC parameters for the database.
Only database owners and system administrators can modify the object isolation attribute of a database.
You are not allowed to rename a database in use. To rename it, connect to another database.
The compatibility mode of an existing database cannot be changed. It can only be specified during creation of the database. For details, see CREATE DATABASE.
Syntax¶
Modify the maximum number of connections of the database.
ALTER DATABASE database_name [ [ WITH ] CONNECTION LIMIT connlimit ];
Rename the database.
ALTER DATABASE database_name RENAME TO new_name;
Note
If the database contains OBS multi-temperature tables, the database name cannot be changed.
Change the database owner.
ALTER DATABASE database_name OWNER TO new_owner;
Change the default tablespace of the database.
ALTER DATABASE database_name SET TABLESPACE new_tablespace;
Note
The current tablespaces cannot be changed to OBS tablespaces.
Modify the session parameter value of the database.
ALTER DATABASE database_name SET configuration_parameter { { TO | = } { value | DEFAULT } | FROM CURRENT };
Reset the database configuration parameter.
ALTER DATABASE database_name RESET { configuration_parameter | ALL };
Modify the object isolation attribute of a database.
ALTER DATABASE database_name [ WITH ] { ENABLE | DISABLE } PRIVATE OBJECT;
Note
To modify the object isolation attribute of a database, the database must be connected. Otherwise, the modification will fail.
For a new database, the object isolation attribute is disabled by default. After this attribute is enabled, common users can view only the objects (such as tables, functions, views, and columns) that they have the permission to access. This attribute does not take effect for administrators. After this attribute is enabled, administrators can still view all database objects.
Parameter Description¶
database_name
Specifies the name of the database whose attributes are to be modified.
Value range: a string. It must comply with the naming convention.
connlimit
Specifies the maximum number of concurrent connections that can be made to this database (excluding administrators' connections).
Value range: The value must be an integer, preferably between 1 and 50. The default value -1 indicates no restrictions.
new_name
Specifies the new name of a database.
Value range: a string. It must comply with the naming convention.
new_owner
Specifies the new owner of a database.
Value range: a string indicating a valid user name
configuration_parameter
value
Sets a specified database session parameter. If the value is DEFAULT or RESET, the default setting is used in the new session. OFF closes the setting.
Value range: a string. It can be set to:
DEFAULT
OFF
RESET
FROM CURRENT
Sets the value based on the database connected to the current session.
RESET configuration_parameter
Resets the specified database session parameter.
RESET ALL
Resets all database session parameters.
Note
Modifies the default tablespace of a database by moving all the tables or indexes from the old tablespace to the new one. This operation does not affect the tables or indexes in other non-default tablespaces.
The modified database session parameter values will take effect in the next session.
Example:¶
Set the maximum number of connections to database music to 10:
ALTER DATABASE music CONNECTION LIMIT= 10;
Change the database name from music to music1.
ALTER DATABASE music RENAME TO music1;
Change the owner of database music1 to tom:
ALTER DATABASE music1 OWNER TO tom;
Set the tablespace of database music1 to PG_DEFAULT:
ALTER DATABASE music1 SET TABLESPACE PG_DEFAULT;
Disable the default index scan on the music1 database.
ALTER DATABASE music1 SET enable_indexscan TO off;
Reset parameter enable_indexscan:
ALTER DATABASE music1 RESET enable_indexscan;