for (String name : names) {
ColumnVar l = lvars.get(name);
ColumnVar r = rvars.get(name);
if (!l.isImplied() && !r.isImplied()) {
IdColumn rid = new IdColumn(r);
SqlExpr filter = eq(rid, new IdColumn(l));
if (r.isNullable()) {
filter = or(isNull(rid), filter);
}
right.addFilter(filter);
}