ALTER DOMAIN
ALTER DOMAIN — change the definition of a domain
Synopsis
ALTER DOMAINname{ SET DEFAULTexpression| DROP DEFAULT }ALTER DOMAINname{ SET | DROP } NOT NULLALTER DOMAINnameADDdomain_constraint[ NOT VALID ]ALTER DOMAINnameDROP CONSTRAINT [ IF EXISTS ]constraint_name[ RESTRICT | CASCADE ]ALTER DOMAINnameRENAME CONSTRAINTconstraint_nameTOnew_constraint_nameALTER DOMAINnameVALIDATE CONSTRAINTconstraint_nameALTER DOMAINnameOWNER TO {new_owner| CURRENT_ROLE | CURRENT_USER | SESSION_USER }ALTER DOMAINnameRENAME TOnew_nameALTER DOMAINnameSET SCHEMAnew_schemawheredomain_constraintis:[ CONSTRAINTconstraint_name]{ NOT NULL | CHECK (expression) }
Description
ALTER DOMAIN changes the definition of an existing domain. There are several sub-forms:
SET/DROP DEFAULTThese forms set or remove the default value for a domain. Note that defaults only apply to subsequent
INSERTcommands; they do not affect rows already in a table using the domain.SET/DROP NOT NULLThese forms change whether a domain is marked to allow NULL values or to reject NULL values. You can only
SET NOT NULLwhen the columns using the domain contain no null values.ADDdomain_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 VALIDoption; the constraint can later be made valid usingALTER DOMAIN ... VALIDATE CONSTRAINT. Newly inserted or updated rows are always checked against all constraints, even those markedNOT VALID.NOT VALIDis only accepted forCHECKconstraints.DROP CONSTRAINT [ IF EXISTS ]This form drops constraints on a domain. If
IF EXISTSis specified and the constraint does not exist, no error is thrown. In this case a notice is issued instead.RENAME CONSTRAINTThis form changes the name of a constraint on a domain.
VALIDATE CONSTRAINTThis 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.OWNERThis form changes the owner of the domain to the specified user.
RENAMEThis form changes the name of the domain.
SET SCHEMAThis 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 useALTER DOMAIN. To change the schema of a domain, you must also haveCREATE privilege on the new schema. To alter the owner, you must be able toSET ROLE to the new owning role, and that role must haveCREATE 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
nameThe name (possibly schema-qualified) of an existing domain to alter.
domain_constraintNew domain constraint for the domain.
constraint_nameName of an existing constraint to drop or rename.
NOT VALIDDo not verify existing stored data for constraint validity.
CASCADEAutomatically drop objects that depend on the constraint, and in turn all objects that depend on those objects (seeSection 5.15).
RESTRICTRefuse to drop the constraint if there are any dependent objects. This is the default behavior.
new_nameThe new name for the domain.
new_constraint_nameThe new name for the constraint.
new_ownerThe user name of the new owner of the domain.
new_schemaThe new schema for the domain.
Notes
AlthoughALTER 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 theNOT VALID option, commit that command, wait until all transactions started before that commit have finished, and then issueALTER 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, andALTER 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 aNOT NULL constraint to a domain:
ALTER DOMAIN zipcode SET NOT NULL;
To remove aNOT 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 theSQL standard, except for theOWNER,RENAME,SET SCHEMA, andVALIDATE CONSTRAINT variants, which arePostgres Pro extensions. TheNOT VALID clause of theADD CONSTRAINT variant is also aPostgres Pro extension.