Function AlterDomainAddConstraint

src/backend/commands/typecmds.c:3035–3144

* AlterDomainAddConstraint * * Implements the ALTER DOMAIN .. ADD CONSTRAINT statement. */

 * Implements the ALTER DOMAIN .. ADD CONSTRAINT statement.
 */
ObjectAddress
AlterDomainAddConstraint(List *names, Node *newConstraint,
						 ObjectAddress *constrAddr)
{
	TypeName   *typename;
	Oid			domainoid;
	Relation	typrel;
	HeapTuple	tup;
	Form_pg_type typTup;
	Constraint *constr;
	char	   *ccbin;
	ObjectAddress address;

	/* Make a TypeName so we can use standard type lookup machinery */
	typename = makeTypeNameFromNameList(names);
	domainoid = typenameTypeId(NULL, typename);

	/* Look up the domain in the type table */
	typrel = table_open(TypeRelationId, RowExclusiveLock);

	tup = SearchSysCacheCopy1(TYPEOID, ObjectIdGetDatum(domainoid));
	if (!HeapTupleIsValid(tup))
		elog(ERROR, "cache lookup failed for type %u", domainoid);
	typTup = (Form_pg_type) GETSTRUCT(tup);

	/* Check it's a domain and check user has permission for ALTER DOMAIN */
	checkDomainOwner(tup);

	if (!IsA(newConstraint, Constraint))
		elog(ERROR, "unrecognized node type: %d",
			 (int) nodeTag(newConstraint));

	constr = (Constraint *) newConstraint;

	switch (constr->contype)
	{
		case CONSTR_CHECK:
			/* processed below */
			break;

		case CONSTR_UNIQUE:
			ereport(ERROR,
					(errcode(ERRCODE_SYNTAX_ERROR),
					 errmsg("unique constraints not possible for domains")));
			break;

		case CONSTR_PRIMARY:
			ereport(ERROR,
					(errcode(ERRCODE_SYNTAX_ERROR),
					 errmsg("primary key constraints not possible for domains")));
			break;

		case CONSTR_EXCLUSION:
			ereport(ERROR,
					(errcode(ERRCODE_SYNTAX_ERROR),
					 errmsg("exclusion constraints not possible for domains")));
			break;