ALTER SERVER

Function

ALTER SERVER adds, modifies, or deletes the parameters of an existing server. You can query existing servers from the pg_foreign_server system catalog.

Precautions

Only the server owner or a user granted with the ALTER permission can run the ALTER SERVER command. The system administrator has this permission by default. To modify a server owner, you must be the server owner or system administrator and a member of the new owner role.

Syntax

• Change the parameters for a foreign server.

  AlterServer ::= ALTER SERVER server_name [ VERSION 'new_version' ]
    [ OPTIONS ( {[ ADD | SET | DROP ] option ['value']} [, ... ] ) ];

  In OPTIONS, ADD, SET, and DROP are operations to be performed. If these operations are not specified, ADD operations will be performed by default. option and value are the parameters of the corresponding operation.

• Change the name of a foreign server.

  AlterServer ::= ALTER SERVER server_name
     RENAME TO new_name;

Parameter Description

• server_name

  Specifies the name of the server to be modified.

• new_version

  Specifies the new version of the server.

• OPTIONS

  Change options of the server. ADD, SET, and DROP are operations to be performed. If the operation is not set explicitly, ADD is used. The option name must be unique, and the name and value are also validated with the foreign data wrapper library of the server.

  • Options supported by oracle_fdw are as follows:

    • dbserver

      Connection string of the remote Oracle database.

    • isolation_level (default value: serializable)

      Oracle database transaction isolation level.

      Value range: serializable, read_committed, read_only

  • Options supported by mysql_fdw are as follows:

    • host (default value: 127.0.0.1)

      IP address of the MySQL server or MariaDB.

    • port (default value: 3306)

      Listening port number of the MySQL server or MariaDB.

  • The options supported by postgres_fdw are the same as those supported by libpq. For details, see Link Parameters. Note that the following options cannot be modified:

    • user and password

      The user name and password are specified when the user mapping is created.

    • client_encoding

      The encoding mode of the local server is automatically obtained and set.

    • application_name

      This option is always set to postgres_fdw.

    In addition to the connection parameters supported by libpq, the following options are provided:

  • use_remote_estimate

    Controls whether postgres_fdw issues the EXPLAIN command to obtain the estimated run time. The default value is false.

  • fdw_startup_cost

    Estimates the startup time required for a foreign table scan, including the time to establish a connection, analyze the request at the remote server, and generate a plan. The default value is 100.

  • fdw_typle_cost

    Specifies the additional consumption when each tuple is scanned on a remote server. The value specifies the extra consumption of data transmission between servers. The default value is 0.01.

• new_name

  Specifies the new name of the server.

Helpful Links

CREATE SERVER，DROP SERVER