How to use org.apache.calcite.rel.type

@Override
public RelDataType getRowType(
    RelDataTypeFactory relDataTypeFactory) {
  RelDataTypeFactory.FieldInfoBuilder b = relDataTypeFactory.builder();
  for (FieldType f : fields) {
    b.add(f.name, f.relDataType);
  }
  return b.build();
}

@Override
public int getDefaultPrecision(final SqlTypeName typeName)
{
 return RelDataTypeSystem.DEFAULT.getDefaultPrecision(typeName);
}

@Override
public int getMaxNumericPrecision()
{
 return RelDataTypeSystem.DEFAULT.getMaxNumericPrecision();
}

private RexNode inputRef(final String columnName)
{
 final int columnNumber = rowSignature.getRowOrder().indexOf(columnName);
 return rexBuilder.makeInputRef(relDataType.getFieldList().get(columnNumber).getType(), columnNumber);
}

private SqlNode maybeCast(SqlNode node, RelDataType currentType,
  RelDataType desiredType) {
  return currentType.equals(desiredType)
    || (currentType.isNullable() != desiredType.isNullable()
        && typeFactory.createTypeWithNullability(currentType,
    desiredType.isNullable()).equals(desiredType))
    ? node
    : SqlStdOperatorTable.CAST.createCall(SqlParserPos.ZERO,
    node, SqlTypeUtil.convertTypeToSpec(desiredType));
}

private void handleOffsetFetch(SqlNode offset, SqlNode fetch) {
  if (offset instanceof SqlDynamicParam) {
    setValidatedNodeType(offset,
      typeFactory.createSqlType(SqlTypeName.INTEGER));
  }
  if (fetch instanceof SqlDynamicParam) {
    setValidatedNodeType(fetch,
      typeFactory.createSqlType(SqlTypeName.INTEGER));
  }
}

 @Override
 public String apply(RelDataTypeField f) {
  return f.getName();
 }
});

  public RelDataType visit(SqlIntervalQualifier intervalQualifier) {
    return typeFactory.createSqlIntervalType(intervalQualifier);
  }
}

@Override
public int getMaxScale(final SqlTypeName typeName)
{
 return RelDataTypeSystem.DEFAULT.getMaxScale(typeName);
}

@Override
public int getMaxPrecision(final SqlTypeName typeName)
{
 return RelDataTypeSystem.DEFAULT.getMaxPrecision(typeName);
}

@Override
public int getMaxNumericScale()
{
 return RelDataTypeSystem.DEFAULT.getMaxNumericScale();
}

@Override
public boolean isSchemaCaseSensitive()
{
 return RelDataTypeSystem.DEFAULT.isSchemaCaseSensitive();
}

@Override
public boolean isCaseSensitive(final SqlTypeName typeName)
{
 return RelDataTypeSystem.DEFAULT.isCaseSensitive(typeName);
}

@Override
public int getNumTypeRadix(final SqlTypeName typeName)
{
 return RelDataTypeSystem.DEFAULT.getNumTypeRadix(typeName);
}

@Override
public String getLiteral(final SqlTypeName typeName, final boolean isPrefix)
{
 return RelDataTypeSystem.DEFAULT.getLiteral(typeName, isPrefix);
}

@Override
public boolean isAutoincrement(final SqlTypeName typeName)
{
 return RelDataTypeSystem.DEFAULT.isAutoincrement(typeName);
}

@Override
public RelDataType deriveRankType(final RelDataTypeFactory typeFactory)
{
 return RelDataTypeSystem.DEFAULT.deriveRankType(typeFactory);
}

@Override
public RelDataType deriveCovarType(
  final RelDataTypeFactory typeFactory,
  final RelDataType arg0Type,
  final RelDataType arg1Type
)
{
 return RelDataTypeSystem.DEFAULT.deriveCovarType(typeFactory, arg0Type, arg1Type);
}

@Override
public RelDataType deriveFractionalRankType(final RelDataTypeFactory typeFactory)
{
 return RelDataTypeSystem.DEFAULT.deriveFractionalRankType(typeFactory);
}

@Override
public RelDataType deriveAvgAggType(
  final RelDataTypeFactory typeFactory,
  final RelDataType argumentType
)
{
 return RelDataTypeSystem.DEFAULT.deriveAvgAggType(typeFactory, argumentType);
}