/**
* Creates an expression which references the <i> fieldOrdinal</i><sup>th</sup> field of the
* <i>ordinal</i><sup>th</sup> input.
*
* <p>(We can potentially optimize the generation process, so we can access field values without
* actually instantiating the row.)
*/
public Expression translateInputField(JavaRel rel, int ordinal, int fieldOrdinal) {
assert ordinal >= 0;
assert ordinal < rel.getInputs().size();
assert fieldOrdinal >= 0;
assert fieldOrdinal < rel.getInput(ordinal).getRowType().getFieldList().size();
RelDataType rowType = rel.getRowType();
final RelDataTypeField[] fields = rowType.getFields();
final int fieldIndex = computeFieldOffset(rel, ordinal) + fieldOrdinal;
assert fieldIndex >= 0;
assert fieldIndex < fields.length;
final RexNode expr = rexBuilder.makeInputRef(fields[fieldIndex].getType(), fieldIndex);
return translate(rel, expr);
}
