ALTER FOREIGN TABLE

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Contents

名称

ALTER FOREIGN TABLE -- change the definition of a foreign table

语法概要
   ALTER FOREIGN TABLE name
       action [, ... ]
   ALTER FOREIGN TABLE name
       RENAME [ COLUMN ] column TO new_column
   ALTER FOREIGN TABLE name
       RENAME TO new_name
   ALTER FOREIGN TABLE name
       SET SCHEMA new_schema
   where action is one of:
       ADD [ COLUMN ] column type [ NULL | NOT NULL ]
       DROP [ COLUMN ] [ IF EXISTS ] column [ RESTRICT | CASCADE ]
       ALTER [ COLUMN ] column [ SET DATA ] TYPE type
       ALTER [ COLUMN ] column { SET | DROP } NOT NULL
       OWNER TO new_owner
       OPTIONS ( [ ADD | SET | DROP ] option ['value'] [, ... ])
描述

ALTER FOREIGN TABLE changes the definition of an existing foreign table. There are several subforms:

ADD COLUMN This form adds a new column to the foreign table, using the same syntax as CREATE FOREIGN TABLE.

DROP COLUMN [ IF EXISTS ] This form drops a column from a foreign table. You will need to say CASCADE if anything outside the table depends on the column; for example, views. If IF EXISTS is specified and the column does not exist, no error is thrown. In this case a notice is issued instead.

SET DATA TYPE This form changes the type of a column of a foreign table.

SET/DROP NOT NULL Mark a column as allowing, or not allowing, null values.

OWNER This form changes the owner of the foreign table to the specified user.

RENAME The RENAME forms change the name of a foreign table or the name of an individual column in a foreign table.

SET SCHEMA This form moves the foreign table into another schema.

OPTIONS ( [ ADD | SET | DROP ] option ['value'] [, ... ] ) Change options for the foreign table. ADD, SET, and DROP specify the action to be performed. ADD is assumed if no operation is explicitly specified. Option names must be unique; names and values are also validated using the foreign data wrapper library.

All the actions except RENAME and SET SCHEMA can be combined into a list of multiple alterations to apply in parallel. For example, it is possible to add several columns and/or alter the type of several columns in a single command.

You must own the table to use ALTER FOREIGN TABLE. To change the schema of a foreign table, you must also have CREATE privilege on the new schema. To alter the owner, you must also be a direct or indirect member of the new owning role, and that role must have CREATE privilege on the table's schema. (These restrictions enforce that altering the owner doesn't do anything you couldn't do by dropping and recreating the table. However, a superuser can alter ownership of any table anyway.)

参数
name
The name (possibly schema-qualified) of an existing foreign table to alter.
column
Name of a new or existing column.
new_column
New name for an existing column.
new_name
New name for the table.
type
Data type of the new column, or new data type for an existing column.
CASCADE
Automatically drop objects that depend on the dropped column (for example, views referencing the column).
RESTRICT
Refuse to drop the column if there are any dependent objects. This is the default behavior.
new_owner
The user name of the new owner of the table.
new_schema
The name of the schema to which the table will be moved.
注意

The key word COLUMN is noise and can be omitted.

Consistency with the foreign server is not checked when a column is added or removed with ADD COLUMN or DROP COLUMN, a NOT NULL constraint is added, or a column type is changed with SET DATA TYPE. It is the user's responsibility to ensure that the table definition matches the remote side.

Refer to CREATE FOREIGN TABLE for a further description of valid parameters.

示例

To mark a column as not-null:

    ALTER FOREIGN TABLE distributors ALTER COLUMN street SET NOT NULL;

To change options of a foreign table:

    ALTER FOREIGN TABLE myschema.distributors OPTIONS (ADD opt1 'value', SET opt2, 'value2', DROP opt3 'value3');
兼容性

The forms ADD, DROP, and SET DATA TYPE conform with the SQL standard. The other forms are PostgreSQL extensions of the SQL standard. Also, the ability to specify more than one manipulation in a single ALTER FOREIGN TABLE command is an extension.

ALTER FOREIGN TABLE DROP COLUMN can be used to drop the only column of a foreign table, leaving a zero-column table. This is an extension of SQL, which disallows zero-column foreign tables.

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