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ALTER DATABASE

Updated at:Mar 13, 2020 GMT+08:00

Function

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

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 of the database.
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    ALTER DATABASE database_name
        [ [ WITH ] CONNECTION LIMIT connlimit ];
    
  • Rename the database.
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    ALTER DATABASE database_name
        RENAME TO new_name;
    
  • Change the database owner.
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    ALTER DATABASE database_name
        OWNER TO new_owner;
    
  • Modify the session parameter value of the database.
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    2
    ALTER DATABASE database_name
        SET configuration_parameter { { TO | = } { value | DEFAULT } | FROM CURRENT };
    
  • Reset the database configuration parameter.
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    ALTER DATABASE database_name RESET
        { configuration_parameter | ALL };
    
  • Modify the object isolation attribute of a database.
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    ALTER DATABASE database_name [ WITH ] { ENABLE | DISABLE } PRIVATE OBJECT;
    
    • 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 compliant with the identifier naming rules

  • 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 compliant with the identifier naming rules

  • 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.

  • 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.

Examples

See the Examples in CREATE DATABASE.

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