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_ROLE | 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
           These forms set or remove the default value for a domain. Note that defaults only
           apply to subsequent INSERT commands; they do not affect rows already in a table using
           the domain.

       SET/DROP NOT NULL
           These forms change whether a domain is marked to allow NULL values or to reject NULL
           values. You can only SET NOT NULL when the columns using the domain contain no null
           values.

       ADD domain_constraint [ NOT VALID ]
           This form adds a new constraint to a domain. When a new constraint is added to a
           domain, all columns using that domain will be checked against the newly added
           constraint. These checks can be suppressed by adding the new constraint using the NOT
           VALID option; the constraint can later be made valid using ALTER DOMAIN ... VALIDATE
           CONSTRAINT. Newly inserted or updated rows are always checked against all constraints,
           even those marked NOT VALID.  NOT VALID is only accepted for CHECK constraints.

       DROP CONSTRAINT [ IF EXISTS ]
           This form drops constraints on a domain. If IF EXISTS is specified and the constraint
           does not exist, no error is thrown. In this case a notice is issued instead.

       RENAME CONSTRAINT
           This form changes the name of a constraint on a domain.

       VALIDATE CONSTRAINT
           This form validates a constraint previously added as NOT VALID, that is, it verifies
           that all values in table columns of the domain type satisfy the specified constraint.

       OWNER
           This form changes the owner of the domain to the specified user.

       RENAME
           This form changes the name of the domain.

       SET SCHEMA
           This form changes the schema of the domain. Any constraints associated with the domain
           are moved into the new schema as well.

       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 be able to SET
       ROLE to 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
           The name (possibly schema-qualified) of an existing domain to alter.

       domain_constraint
           New domain constraint for the domain.

       constraint_name
           Name of an existing constraint to drop or rename.

       NOT VALID
           Do not verify existing stored data for constraint validity.

       CASCADE
           Automatically drop objects that depend on the constraint, and in turn all objects that
           depend on those objects (see Section 5.15).

       RESTRICT
           Refuse to drop the constraint if there are any dependent objects. This is the default
           behavior.

       new_name
           The new name for the domain.

       new_constraint_name
           The new name for the constraint.

       new_owner
           The user name of the new owner of the domain.

       new_schema
           The new schema for the domain.

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))