How to use

explicit

method

in

org.apache.calcite.sql.type.ReturnTypes

 ApproxCountDistinctSqlAggFunction()
 {
  super(
    NAME,
    null,
    SqlKind.OTHER_FUNCTION,
    ReturnTypes.explicit(SqlTypeName.BIGINT),
    InferTypes.VARCHAR_1024,
    OperandTypes.ANY,
    SqlFunctionCategory.STRING,
    false,
    false
  );
 }
}

public OperatorBuilder nullableReturnType(final SqlTypeName typeName)
{
 this.returnTypeInference = ReturnTypes.explicit(
   factory -> Calcites.createSqlTypeWithNullability(factory, typeName, true)
 );
 return this;
}

public OperatorBuilder returnType(final SqlTypeName typeName)
{
 this.returnTypeInference = ReturnTypes.explicit(
   factory -> Calcites.createSqlType(factory, typeName)
 );
 return this;
}

private static CalciteUDFInfo getUDFInfo(String hiveUdfName,
  ImmutableList<RelDataType> calciteArgTypes, RelDataType calciteRetType) {
 CalciteUDFInfo udfInfo = new CalciteUDFInfo();
 udfInfo.udfName = hiveUdfName;
 udfInfo.returnTypeInference = ReturnTypes.explicit(calciteRetType);
 udfInfo.operandTypeInference = InferTypes.explicit(calciteArgTypes);
 ImmutableList.Builder<SqlTypeFamily> typeFamilyBuilder = new ImmutableList.Builder<SqlTypeFamily>();
 for (RelDataType at : calciteArgTypes) {
  typeFamilyBuilder.add(Util.first(at.getSqlTypeName().getFamily(), SqlTypeFamily.ANY));
 }
 udfInfo.operandTypeChecker = OperandTypes.family(typeFamilyBuilder.build());
 return udfInfo;
}

@Override
public AggregateCall other(RelDataTypeFactory typeFactory, AggregateCall e) {
 RelDataType countRetType = typeFactory.createTypeWithNullability(typeFactory.createSqlType(SqlTypeName.BIGINT), true);
 return AggregateCall.create(
  new HiveSqlCountAggFunction(isDistinct, ReturnTypes.explicit(countRetType), operandTypeInference, operandTypeChecker),
  false, ImmutableIntList.of(), -1, countRetType, "count");
}

@Override
public AggregateCall other(RelDataTypeFactory typeFactory, AggregateCall e) {
 RelDataType countRetType = typeFactory.createTypeWithNullability(typeFactory.createSqlType(SqlTypeName.BIGINT), true);
 return AggregateCall.create(
  new HiveSqlCountAggFunction(isDistinct, ReturnTypes.explicit(countRetType), operandTypeInference, operandTypeChecker),
  false, ImmutableIntList.of(), -1, countRetType, "count");
}

SqlAggFunction createCustomAggFunction(String funcName, RelDataType returnType, Class<?> customAggFuncClz) {
  RelDataTypeFactory typeFactory = getCluster().getTypeFactory();
  SqlIdentifier sqlIdentifier = new SqlIdentifier(funcName, new SqlParserPos(1, 1));
  AggregateFunction aggFunction = AggregateFunctionImpl.create(customAggFuncClz);
  List<RelDataType> argTypes = new ArrayList<RelDataType>();
  List<SqlTypeFamily> typeFamilies = new ArrayList<SqlTypeFamily>();
  for (FunctionParameter o : aggFunction.getParameters()) {
    final RelDataType type = o.getType(typeFactory);
    argTypes.add(type);
    typeFamilies.add(Util.first(type.getSqlTypeName().getFamily(), SqlTypeFamily.ANY));
  }
  return new SqlUserDefinedAggFunction(sqlIdentifier, ReturnTypes.explicit(returnType),
      InferTypes.explicit(argTypes), OperandTypes.family(typeFamilies), aggFunction, false, false,
      typeFactory);
}

 QuantileSqlAggFunction()
 {
  super(
    NAME,
    null,
    SqlKind.OTHER_FUNCTION,
    ReturnTypes.explicit(SqlTypeName.DOUBLE),
    null,
    OperandTypes.or(
      OperandTypes.and(
        OperandTypes.sequence(SIGNATURE1, OperandTypes.ANY, OperandTypes.LITERAL),
        OperandTypes.family(SqlTypeFamily.ANY, SqlTypeFamily.NUMERIC)
      ),
      OperandTypes.and(
        OperandTypes.sequence(SIGNATURE2, OperandTypes.ANY, OperandTypes.LITERAL, OperandTypes.LITERAL),
        OperandTypes.family(SqlTypeFamily.ANY, SqlTypeFamily.NUMERIC, SqlTypeFamily.EXACT_NUMERIC)
      )
    ),
    SqlFunctionCategory.NUMERIC,
    false,
    false
  );
 }
}

private static CalciteUDFInfo getUDFInfo(String hiveUdfName,
  ImmutableList<RelDataType> calciteArgTypes, RelDataType calciteRetType) {
 CalciteUDFInfo udfInfo = new CalciteUDFInfo();
 udfInfo.udfName = hiveUdfName;
 udfInfo.returnTypeInference = ReturnTypes.explicit(calciteRetType);
 udfInfo.operandTypeInference = InferTypes.explicit(calciteArgTypes);
 ImmutableList.Builder<SqlTypeFamily> typeFamilyBuilder = new ImmutableList.Builder<SqlTypeFamily>();
 for (RelDataType at : calciteArgTypes) {
  typeFamilyBuilder.add(Util.first(at.getSqlTypeName().getFamily(), SqlTypeFamily.ANY));
 }
 udfInfo.operandTypeChecker = OperandTypes.family(typeFamilyBuilder.build());
 return udfInfo;
}

new SqlFunction(
  type.getSqlIdentifier(),
  ReturnTypes.explicit(type),
  null,
  null,

new HiveSqlSumAggFunction(
  oldCall.isDistinct(),
  ReturnTypes.explicit(sumReturnType),
  oldCall.getAggregation().getOperandTypeInference(),
new HiveSqlCountAggFunction(
  oldCall.isDistinct(),
  ReturnTypes.explicit(countRetType),
  oldCall.getAggregation().getOperandTypeInference(),

new HiveSqlSumAggFunction(
  oldCall.isDistinct(),
  ReturnTypes.explicit(sumSquaredReturnType),
  InferTypes.explicit(Collections.singletonList(argSquared.getType())),
new HiveSqlSumAggFunction(
  oldCall.isDistinct(),
  ReturnTypes.explicit(sumReturnType),
  InferTypes.explicit(Collections.singletonList(argOrdinalType)),
new HiveSqlCountAggFunction(
  oldCall.isDistinct(),
  ReturnTypes.explicit(countRetType),
  oldCall.getAggregation().getOperandTypeInference(),

new HiveSqlSumAggFunction(
  oldCall.isDistinct(),
  ReturnTypes.explicit(sumReturnType),
  oldCall.getAggregation().getOperandTypeInference(),

SqlDefaultOperator() {
 super("DEFAULT", SqlKind.DEFAULT, 100, true,
   ReturnTypes.explicit(SqlTypeName.ANY), InferTypes.RETURN_TYPE,
   OperandTypes.NILADIC);
}

SqlDefaultOperator() {
 super("DEFAULT", SqlKind.DEFAULT, 100, true,
   ReturnTypes.explicit(SqlTypeName.ANY), InferTypes.RETURN_TYPE,
   OperandTypes.NILADIC);
}

/**
 * Creates an inference rule which returns a copy of a given data type.
 */
public static ExplicitReturnTypeInference explicit(RelDataType type) {
 return explicit(RelDataTypeImpl.proto(type));
}

/**
 * Creates an inference rule which returns a copy of a given data type.
 */
public static ExplicitReturnTypeInference explicit(RelDataType type) {
 return explicit(RelDataTypeImpl.proto(type));
}

/**
 * Creates an inference rule which returns a type with no precision or scale,
 * such as {@code DATE}.
 */
public static ExplicitReturnTypeInference explicit(SqlTypeName typeName) {
 return explicit(RelDataTypeImpl.proto(typeName, false));
}

/**
 * Creates an inference rule which returns a type with no precision or scale,
 * such as {@code DATE}.
 */
public static ExplicitReturnTypeInference explicit(SqlTypeName typeName) {
 return explicit(RelDataTypeImpl.proto(typeName, false));
}

public SqlJsonApiCommonSyntaxOperator() {
 super("JSON_API_COMMON_SYNTAX", SqlKind.JSON_API_COMMON_SYNTAX, 100, true,
   ReturnTypes.explicit(SqlTypeName.ANY), null,
   OperandTypes.family(SqlTypeFamily.ANY, SqlTypeFamily.STRING));
}