only one namespace allowed by a authid at pg_namespace table?

only one namespace allowed by a authid at pg_namespace table? for in the
function:
static void recomputeNamespacePath(void){
...
if (strcmp(curname, "$user") == 0)
{
/* $user --- substitute namespace matching user name, if any */
HeapTuple tuple;

tuple = SearchSysCache(AUTHOID,
ObjectIdGetDatum(roleid),
0, 0, 0);
if (HeapTupleIsValid(tuple))
{
char *rname;

rname = NameStr(((Form_pg_authid)
GETSTRUCT(tuple))->rolname);
namespaceId = GetSysCacheOid(NAMESPACENAME,
CStringGetDatum(rname),
0, 0, 0);
ReleaseSysCache(tuple);
if (OidIsValid(namespaceId) &&
!list_member_oid(oidlist, namespaceId) &&
pg_namespace_aclcheck(namespaceId, roleid,
ACL_USAGE) == ACLCHECK_OK)
oidlist = lappend_oid(oidlist, namespaceId);
}
}
}
...
}
I noticed with the revoke of function GetSysCacheOid(NAMESPACENAME,
CStringGetDatum(rname),0, 0, 0); only return one oid of namespace.