CLEAN CONNECTION

Function

Clears database connections. You may use this statement to delete a specific user's connections to a specified database.

Precautions

• openGauss does not support specified nodes and supports only TO ALL.

• This function can be used to clear the normal connections that are being used only in force mode.

Syntax

CLEAN CONNECTION
      TO { COORDINATOR ( nodename [, ... ] ) | NODE ( nodename [, ... ] )| ALL [ CHECK ] [ FORCE ] }
      [ FOR DATABASE dbname ]
      [ TO USER username ];

Parameters

• CHECK

  This parameter can be specified only when the node list is specified as TO ALL. Setting this parameter will check whether a database is accessed by other sessions before its connections are cleared. If any sessions are detected before DROP DATABASE is executed, an error will be reported and the database will not be deleted.

• FORCE

  This parameter can be specified only when the node list is specified as TO ALL. Setting this parameter will send SIGTERM signals to all the threads related to the specified dbname and username and forcibly shut them down.

• COORDINATOR ( nodename [, … ] ) | NODE ( nodename [, … ] ) | ALL

  Deletes connections to a specified instance. There are three scenarios:

  • Deletes connections on a specified CN. openGauss does not support this scenario.
  • Deletes connections on a specified DN. openGauss does not support this scenario.
  • Deletes connections on all nodes(TO ALL). openGauss supports only this scenario.

• dbname

  Deletes connections to a specified database. If this parameter is not specified, connections to all databases will be deleted.

  Value range: an existing database name

• username

  Deletes connections of a specific user. If this parameter is not specified, connections of all users will be deleted.

  Value range: an existing username

Examples

--Create user **jack**.
CREATE USER jack PASSWORD 'Bigdata123@';

--Clean the user **jack**'s connections to the postgres database:
CLEAN CONNECTION TO ALL FOR DATABASE template1 TO USER jack;

--Delete all connections of user **jack**.
CLEAN CONNECTION TO ALL TO USER jack;

--Clean all the connections to the **gaussdb** database.
CLEAN CONNECTION TO ALL FORCE FOR DATABASE gaussdb;

--Delete the user **jack**.
DROP USER jack;