How to use

useDoubleMultiplication

method

in

org.apache.calcite.rel.type.RelDataTypeFactory

private RexNode expandTimes(RexCall call, List<RexNode> operands) {
 // Multiplying the internal values of the two arguments leads to
 // a number with scale = scaleA + scaleB. If the result type has
 // a lower scale, then the number should be scaled down.
 int divisor = scaleA + scaleB - call.getType().getScale();
 if (builder.getTypeFactory().useDoubleMultiplication(
   typeA,
   typeB)) {
  // Approximate implementation:
  // cast (a as double) * cast (b as double)
  //     / 10^divisor
  RexNode division =
    makeDivide(
      makeMultiply(
        ensureType(real8, accessValue(operands.get(0))),
        ensureType(real8, accessValue(operands.get(1)))),
      makeApproxLiteral(BigDecimal.TEN.pow(divisor)));
  return encodeValue(division, call.getType(), true);
 } else {
  // Exact implementation: scaleDown(a * b)
  return encodeValue(
    scaleDown(
      builder.makeCall(
        call.getOperator(),
        accessValue(operands.get(0)),
        accessValue(operands.get(1))),
      divisor),
    call.getType());
 }
}

private RexNode expandTimes(RexCall call, List<RexNode> operands) {
 // Multiplying the internal values of the two arguments leads to
 // a number with scale = scaleA + scaleB. If the result type has
 // a lower scale, then the number should be scaled down.
 int divisor = scaleA + scaleB - call.getType().getScale();
 if (builder.getTypeFactory().useDoubleMultiplication(
   typeA,
   typeB)) {
  // Approximate implementation:
  // cast (a as double) * cast (b as double)
  //     / 10^divisor
  RexNode division =
    makeDivide(
      makeMultiply(
        ensureType(real8, accessValue(operands.get(0))),
        ensureType(real8, accessValue(operands.get(1)))),
      makeApproxLiteral(BigDecimal.TEN.pow(divisor)));
  return encodeValue(division, call.getType(), true);
 } else {
  // Exact implementation: scaleDown(a * b)
  return encodeValue(
    scaleDown(
      builder.makeCall(
        call.getOperator(),
        accessValue(operands.get(0)),
        accessValue(operands.get(1))),
      divisor),
    call.getType());
 }
}