NAME¶

ALTER_DOMAIN - change the definition of a domain

SYNOPSIS¶

ALTER DOMAIN name


    { SET DEFAULT expression | DROP DEFAULT }
ALTER DOMAIN name


    { SET | DROP } NOT NULL
ALTER DOMAIN name


    ADD domain_constraint [ NOT VALID ]
ALTER DOMAIN name


    DROP CONSTRAINT [ IF EXISTS ] constraint_name [ RESTRICT | CASCADE ]
ALTER DOMAIN name


     RENAME CONSTRAINT constraint_name TO new_constraint_name
ALTER DOMAIN name


    VALIDATE CONSTRAINT constraint_name
ALTER DOMAIN name


    OWNER TO { new_owner | CURRENT_USER | SESSION_USER }
ALTER DOMAIN name


    RENAME TO new_name
ALTER DOMAIN name


    SET SCHEMA new_schema
where domain_constraint is:
[ CONSTRAINT constraint_name ]
{ NOT NULL | CHECK (expression) }

DESCRIPTION¶

ALTER DOMAIN changes the definition of an existing domain. There are several sub-forms:

SET/DROP DEFAULT

SET/DROP NOT NULL

ADD domain_constraint [ NOT VALID ]

DROP CONSTRAINT [ IF EXISTS ]

RENAME CONSTRAINT

VALIDATE CONSTRAINT

OWNER

RENAME

SET SCHEMA

You must own the domain to use ALTER DOMAIN. To change the schema of a domain, 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 domain's schema. (These restrictions enforce that altering the owner doesn't do anything you couldn't do by dropping and recreating the domain. However, a superuser can alter ownership of any domain anyway.)

PARAMETERS¶

name

domain_constraint

constraint_name

NOT VALID

CASCADE

RESTRICT

new_name

new_constraint_name

new_owner

new_schema

NOTES¶

Although ALTER DOMAIN ADD CONSTRAINT attempts to verify that existing stored data satisfies the new constraint, this check is not bulletproof, because the command cannot “see” table rows that are newly inserted or updated and not yet committed. If there is a hazard that concurrent operations might insert bad data, the way to proceed is to add the constraint using the NOT VALID option, commit that command, wait until all transactions started before that commit have finished, and then issue ALTER DOMAIN VALIDATE CONSTRAINT to search for data violating the constraint. This method is reliable because once the constraint is committed, all new transactions are guaranteed to enforce it against new values of the domain type.

Currently, ALTER DOMAIN ADD CONSTRAINT, ALTER DOMAIN VALIDATE CONSTRAINT, and ALTER DOMAIN SET NOT NULL will fail if the named domain or any derived domain is used within a container-type column (a composite, array, or range column) in any table in the database. They should eventually be improved to be able to verify the new constraint for such nested values.

EXAMPLES¶

To add a NOT NULL constraint to a domain:

ALTER DOMAIN zipcode SET NOT NULL;

To remove a NOT NULL constraint from a domain:

ALTER DOMAIN zipcode DROP NOT NULL;

To add a check constraint to a domain:

ALTER DOMAIN zipcode ADD CONSTRAINT zipchk CHECK (char_length(VALUE) = 5);

To remove a check constraint from a domain:

ALTER DOMAIN zipcode DROP CONSTRAINT zipchk;

To rename a check constraint on a domain:

ALTER DOMAIN zipcode RENAME CONSTRAINT zipchk TO zip_check;

To move the domain into a different schema:

ALTER DOMAIN zipcode SET SCHEMA customers;

COMPATIBILITY¶

ALTER DOMAIN conforms to the SQL standard, except for the OWNER, RENAME, SET SCHEMA, and VALIDATE CONSTRAINT variants, which are PostgreSQL extensions. The NOT VALID clause of the ADD CONSTRAINT variant is also a PostgreSQL extension.

SEE ALSO¶

CREATE DOMAIN (CREATE_DOMAIN(7)), DROP DOMAIN (DROP_DOMAIN(7))