[CF 5769] v1 - make ALTER DOMAIN VALIDATE CONSTRAINT no-op when constraint is validated

This branch was automatically generated by a robot using patches from an
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https://commitfest.postgresql.org/patch/5769

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
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Patch(es): https://www.postgresql.org/message-id/CACJufxG=-Dv9fPJHqkA9c-wGZ2dDOWOXSp-X-0K_G7r-DgaASw@mail.gmail.com
Author(s): Jian He

Author: Commitfest Bot

src/backend/commands/typecmds.c

@@ -3087,24 +3087,29 @@ AlterDomainValidateConstraint(List *names, const char *constrName)
 				 errmsg("constraint \"%s\" of domain \"%s\" is not a check constraint",
 						constrName, TypeNameToString(typename))));
 
-	val = SysCacheGetAttrNotNull(CONSTROID, tuple, Anum_pg_constraint_conbin);
-	conbin = TextDatumGetCString(val);
+	if (!con->convalidated)
+	{
+		val = SysCacheGetAttrNotNull(CONSTROID, tuple, Anum_pg_constraint_conbin);
+		conbin = TextDatumGetCString(val);
 
-	validateDomainCheckConstraint(domainoid, conbin);
+		validateDomainCheckConstraint(domainoid, conbin);
 
-	/*
-	 * Now update the catalog, while we have the door open.
-	 */
-	copyTuple = heap_copytuple(tuple);
-	copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
-	copy_con->convalidated = true;
-	CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
+		/*
+		 * Now update the catalog, while we have the door open.
+		*/
+		copyTuple = heap_copytuple(tuple);
+		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
+		copy_con->convalidated = true;
+		CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
 
-	InvokeObjectPostAlterHook(ConstraintRelationId, con->oid, 0);
+		InvokeObjectPostAlterHook(ConstraintRelationId, con->oid, 0);
 
-	ObjectAddressSet(address, TypeRelationId, domainoid);
+		ObjectAddressSet(address, TypeRelationId, domainoid);
 
-	heap_freetuple(copyTuple);
+		heap_freetuple(copyTuple);
+	}
+	else
+		address = InvalidObjectAddress; /* already validated */
 
 	systable_endscan(scan);