presto-main/src/main/java/io/prestosql/operator/aggregation/DecimalSumAggregation.java/DecimalSumAggregation/generateAggregation
class DecimalSumAggregation:    private static InternalAggregationFunction generateAggregation(Type inputType, Type outputType)
    {
        checkArgument(inputType instanceof DecimalType, "type must be Decimal");
        DynamicClassLoader classLoader = new DynamicClassLoader(DecimalSumAggregation.class.getClassLoader());
        List<Type> inputTypes = ImmutableList.of(inputType);
        MethodHandle inputFunction;
        Class<? extends AccumulatorState> stateInterface = LongDecimalWithOverflowState.class;
        AccumulatorStateSerializer<?> stateSerializer = new LongDecimalWithOverflowStateSerializer();

        if (((DecimalType) inputType).isShort()) {
            inputFunction = SHORT_DECIMAL_INPUT_FUNCTION;
        }
        else {
            inputFunction = LONG_DECIMAL_INPUT_FUNCTION;
        }

        AggregationMetadata metadata = new AggregationMetadata(
                generateAggregationName(NAME, outputType.getTypeSignature(), inputTypes.stream().map(Type::getTypeSignature).collect(toImmutableList())),
                createInputParameterMetadata(inputType),
                inputFunction.bindTo(inputType),
                Optional.empty(),
                COMBINE_FUNCTION,
                LONG_DECIMAL_OUTPUT_FUNCTION.bindTo(outputType),
                ImmutableList.of(new AccumulatorStateDescriptor(
                        stateInterface,
                        stateSerializer,
                        new LongDecimalWithOverflowStateFactory())),
                outputType);

        Type intermediateType = stateSerializer.getSerializedType();
        GenericAccumulatorFactoryBinder factory = AccumulatorCompiler.generateAccumulatorFactoryBinder(metadata, classLoader);
        return new InternalAggregationFunction(NAME, inputTypes, ImmutableList.of(intermediateType), outputType, true, false, factory);
    }