/**
   * Returns true if a type is a simple cast of another type. It is if the cast type is nullable and
   * the cast is one of the following:
   * <li>x TO x
   * <li>char(n) TO varchar(m)
   * <li>varchar(n) TO varchar(m)
   * <li>x not null TO x nullable
   *
   * @param origType original type passed into the cast operand
   * @param castType type the operand will be casted to
   * @return true if the cast is simple
   */
  private boolean isCastSimple(RelDataType origType, RelDataType castType) {
    SqlTypeName origTypeName = origType.getSqlTypeName();
    SqlTypeName castTypeName = castType.getSqlTypeName();

    if (!(castType.isNullable())) {
      return false;
    }

    Charset origCharset = origType.getCharset();
    Charset castCharset = castType.getCharset();
    if ((origCharset != null) || (castCharset != null)) {
      if ((origCharset == null) || (castCharset == null)) {
        return false;
      }
      if (!origCharset.equals(castCharset)) {
        return false;
      }
    }

    return ((origType == castType)
        || ((origTypeName == SqlTypeName.CHAR) && (castTypeName == SqlTypeName.VARCHAR))
        || ((origTypeName == SqlTypeName.VARCHAR) && (castTypeName == SqlTypeName.VARCHAR))
        || ((origTypeName == castTypeName)
            && (origType.getPrecision() == castType.getPrecision())
            && ((origTypeName != SqlTypeName.DECIMAL)
                || (origType.getScale() == castType.getScale()))
            && (!origType.isNullable() && castType.isNullable())));
  }
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  /**
   * Determines whether a {@link RexCall} requires decimal expansion. It usually requires expansion
   * if it has decimal operands.
   *
   * <p>Exceptions to this rule are:
   *
   * <ul>
   *   <li>isNull doesn't require expansion
   *   <li>It's okay to cast decimals to and from char types
   *   <li>It's okay to cast nulls as decimals
   *   <li>Casts require expansion if their return type is decimal
   *   <li>Reinterpret casts can handle a decimal operand
   * </ul>
   *
   * @param expr expression possibly in need of expansion
   * @param recurse whether to check nested calls
   * @return whether the expression requires expansion
   */
  public static boolean requiresDecimalExpansion(RexNode expr, boolean recurse) {
    if (!(expr instanceof RexCall)) {
      return false;
    }
    RexCall call = (RexCall) expr;

    boolean localCheck = true;
    switch (call.getKind()) {
      case Reinterpret:
      case IsNull:
        localCheck = false;
        break;
      case Cast:
        RelDataType lhsType = call.getType();
        RelDataType rhsType = call.operands[0].getType();
        if (rhsType.getSqlTypeName() == SqlTypeName.NULL) {
          return false;
        }
        if (SqlTypeUtil.inCharFamily(lhsType) || SqlTypeUtil.inCharFamily(rhsType)) {
          localCheck = false;
        } else if (SqlTypeUtil.isDecimal(lhsType) && (lhsType != rhsType)) {
          return true;
        }
        break;
      default:
        localCheck = call.getOperator().requiresDecimalExpansion();
    }

    if (localCheck) {
      if (SqlTypeUtil.isDecimal(call.getType())) {
        // NOTE jvs 27-Mar-2007: Depending on the type factory, the
        // result of a division may be decimal, even though both inputs
        // are integer.
        return true;
      }
      for (int i = 0; i < call.operands.length; i++) {
        if (SqlTypeUtil.isDecimal(call.operands[i].getType())) {
          return true;
        }
      }
    }
    return (recurse && requiresDecimalExpansion(call.operands, recurse));
  }