super(
cluster, traits, table, catalogReader, child, operation,
updateColumnList, flattened);
assert child.getConvention() instanceof JdbcConvention;
assert getConvention() instanceof JdbcConvention;
final ModifiableTable modifiableTable =
table.unwrap(ModifiableTable.class);
if (modifiableTable == null) {
throw new AssertionError(); // TODO: user error in validator
}
this.expression = table.getExpression(Queryable.class);