CLEAN CONNECTION

Function

CLEAN CONNECTION clears database connections when a database is abnormal. You may use this statement to delete a specific user's connections to a specified database.

Precautions

None

Syntax

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

Parameter Description

• 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 ,nodename ... } ) | NODE ( nodename , nodename ... ) | ALL

  Deletes connections on a specified node. There are three scenarios:

  • Deletes connections to a specified CN.
  • Deletes connections to a specified DN.
  • Deletes connections to all CNs and DNs.

  Value range: nodename is an existing node name.

• dbname

  Deletes connections to a specific 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 user name

Examples

Clean connections to nodes dn1 and dn2 for the template1 database.

1

CLEAN CONNECTION TO NODE (dn_6001_6002,dn_6003_6004) FOR DATABASE template1;

Clean user jack's connections to dn1.

1

CLEAN CONNECTION TO NODE (dn_6001_6002) TO USER jack;

Delete all connections to the postgres database.

1

CLEAN CONNECTION TO ALL FORCE FOR DATABASE postgres;