ALTER DATABASE

Function

ALTER DATABASE modifies a database, including its name, owner, connection limitation, and object isolation.

Precautions

• 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.

Syntax

• Modify the maximum number of connections to the database.

  ALTER DATABASE database_name 
      [ [ WITH ] CONNECTION LIMIT connlimit ];
  

• Rename the database.

  ALTER DATABASE database_name 
      RENAME TO new_name;
  

• 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;
  

• 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 the 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 rule.

• 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 from 1 to 50. The default value -1 indicates that there is no restriction on the number of concurrent connections.

• new_name

  Specifies the new name of a database.

  Value range: a string. It must comply with the naming convention rule.

• new_owner

  Specifies the new owner of a database.

  Value range: a string. It must be a valid username.

• new_tablespace

  Specifies the new default tablespace of a database. The tablespace exists in the database. The default tablespace is pg_default.

  Value range: a string. It must be a valid tablespace name.

• configuration_parameter

  value

  Sets a specified database session parameter to a specified value. If the value is DEFAULT or RESET, the default setting is used in the new session. OFF closes the setting.

  Value range: a string

  • DEFAULT
  • OFF
  • RESET

• FROM CURRENT

  Sets the value of the database based on the current connected session.

• RESET configuration_parameter

  Resets the specified database session parameter.

• RESET ALL

  Resets all database session parameters.

NOTE:

• Modify the default tablespace of a database by moving the table or index in the old tablespace into the new tablespace. 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.

Examples

See Examples in CREATE DATABASE.

Helpful Links

CREATE DATABASE and DROP DATABASE