ALTER FOREIGN TABLE
Synopsis
ALTER FOREIGN TABLE [ IF EXISTS ]nameaction [, ... ]ALTER FOREIGN TABLE [ IF EXISTS ]name RENAME [ COLUMN ]column_name TOnew_column_nameALTER FOREIGN TABLE [ IF EXISTS ]name RENAME TOnew_nameALTER FOREIGN TABLE [ IF EXISTS ]name SET SCHEMAnew_schemawhereaction is one of: ADD [ COLUMN ]column_namedata_type [ COLLATEcollation ] [column_constraint [ ... ] ] DROP [ COLUMN ] [ IF EXISTS ]column_name [ RESTRICT | CASCADE ] ALTER [ COLUMN ]column_name [ SET DATA ] TYPEdata_type ALTER [ COLUMN ]column_name SET DEFAULTexpression ALTER [ COLUMN ]column_name DROP DEFAULT ALTER [ COLUMN ]column_name { SET | DROP } NOT NULL ALTER [ COLUMN ]column_name SET STATISTICSinteger ALTER [ COLUMN ]column_name SET (attribute_option =value [, ... ] ) ALTER [ COLUMN ]column_name RESET (attribute_option [, ... ] ) ALTER [ COLUMN ]column_name OPTIONS ( [ ADD | SET | DROP ]option ['value'] [, ... ]) DISABLE TRIGGER [trigger_name | ALL | USER ] ENABLE TRIGGER [trigger_name | ALL | USER ] ENABLE REPLICA TRIGGERtrigger_name ENABLE ALWAYS TRIGGERtrigger_name OWNER TOnew_owner OPTIONS ( [ ADD | SET | DROP ]option ['value'] [, ... ])Description
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 asCREATE FOREIGN TABLE. Unlike the case when adding a column to a regular table, nothing happens to the underlying storage: this action simply declares that some new column is now accessible through the foreign table.
- DROP COLUMN [ IF EXISTS ]
This form drops a column from a foreign table. You will need to sayCASCADE if anything outside the table depends on the column; for example, views. IfIF EXISTS is specified and the column does not exist, no error is thrown. In this case a notice is issued instead.
- IF EXISTS
Do not throw an error if the foreign table does not exist. A notice is issued in this case.
- SET DATA TYPE
This form changes the type of a column of a foreign table.
- SET/DROP DEFAULT
These forms set or remove the default value for a column. Default values only apply in subsequentINSERT orUPDATE commands; they do not cause rows already in the table to change.
- SET/DROP NOT NULL
Mark a column as allowing, or not allowing, null values.
- SET STATISTICS
This form sets the per-column statistics-gathering target for subsequentANALYZE operations. See the similar form ofALTER TABLE for more details.
- SET (attribute_option =value [, ... ] )
RESET (attribute_option [, ... ] ) This form sets or resets per-attribute options. See the similar form ofALTER TABLE for more details.
- DISABLE/ENABLE [ REPLICA | ALWAYS ] TRIGGER
These forms configure the firing of trigger(s) belonging to the foreign table. See the similar form ofALTER TABLE for more details.
- OWNER
This form changes the owner of the foreign table to the specified user.
- RENAME
TheRENAME 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 or one of its columns.ADD,SET, andDROP specify the action to be performed.ADD is assumed if no operation is explicitly specified. Duplicate option names are not allowed (although it's OK for a table option and a column option to have the same name). Option names and values are also validated using the foreign data wrapper library.
All the actions exceptRENAME andSET 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 useALTER FOREIGN TABLE. To change the schema of a foreign table, you must also haveCREATE 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 haveCREATE 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.) To add a column or alter a column type, you must also haveUSAGE privilege on the data type.
Parameters
- name
The name (possibly schema-qualified) of an existing foreign table to alter.
- column_name
Name of a new or existing column.
- new_column_name
New name for an existing column.
- new_name
New name for the table.
- data_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.
- trigger_name
Name of a single trigger to disable or enable.
- ALL
Disable or enable all triggers belonging to the foreign table. (This requires superuser privilege if any of the triggers are internally generated triggers. The core system does not add such triggers to foreign tables, but add-on code could do so.)
- USER
Disable or enable all triggers belonging to the foreign table except for internally generated triggers.
- 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.
Notes
The key wordCOLUMN is noise and can be omitted.
Consistency with the foreign server is not checked when a column is added or removed withADD COLUMN orDROP COLUMN, aNOT NULL constraint is added, or a column type is changed withSET DATA TYPE. It is the user's responsibility to ensure that the table definition matches the remote side.
Refer toCREATE FOREIGN TABLE for a further description of valid parameters.
Examples
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');
Compatibility
The formsADD,DROP, andSET DATA TYPE conform with the SQL standard. The other forms arePostgreSQL extensions of the SQL standard. Also, the ability to specify more than one manipulation in a singleALTER 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.