static constexpr auto name = "coalesce";

mutable FunctionBasePtr func_is_not_null;

static FunctionPtr create() { return std::make_shared<FunctionCoalesce>(); }

String get_name() const override { return name; }

bool use_default_implementation_for_nulls() const override { return false; }

bool is_variadic() const override { return true; }

size_t get_number_of_arguments() const override { return 0; }

DataTypePtr get_return_type_impl(const DataTypes& arguments) const override {

DataTypePtr res;

for (const auto& arg : arguments) {

if (!arg->is_nullable()) {

res = arg;

break;

}

}

res = res ? res : arguments[0];

const ColumnsWithTypeAndName is_not_null_col {{nullptr, make_nullable(res), ""}};

func_is_not_null = SimpleFunctionFactory::instance().get_function(

"is_not_null_pred", is_not_null_col, std::make_shared<DataTypeUInt8>());

return res;

}

Status execute_impl(FunctionContext* context, Block& block, const ColumnNumbers& arguments,

uint32_t result, size_t input_rows_count) const override {

DCHECK_GE(arguments.size(), 1);

DataTypePtr result_type = block.get_by_position(result).type;

ColumnNumbers filtered_args;

filtered_args.reserve(arguments.size());

for (size_t i = 0; i < arguments.size(); ++i) {

const auto& arg_type = block.get_by_position(arguments[i]).type;

filtered_args.push_back(arguments[i]);

if (!arg_type->is_nullable()) {

if (i == 0) {

block.get_by_position(result).column =

block.get_by_position(arguments[0])

.column->clone_resized(input_rows_count);

return Status::OK();

} else {

break;

}

}

}

size_t remaining_rows = input_rows_count;

size_t argument_size = filtered_args.size();

std::vector<uint32_t> record_idx(

input_rows_count,

0); //used to save column idx, record the result data of each row from which column

std::vector<uint8_t> filled_flags(

input_rows_count,

0); //used to save filled flag, in order to check current row whether have filled data

MutableColumnPtr result_column;

if (!result_type->is_nullable()) {

result_column = result_type->create_column();

} else {

result_column = remove_nullable(result_type)->create_column();

}

// because now the string types does not support random position writing,

// so insert into result data have two methods, one is for string types, one is for others type remaining

bool is_string_result = result_column->is_column_string();

if (is_string_result) {

result_column->reserve(input_rows_count);

} else {

result_column->insert_many_defaults(input_rows_count);

}

auto return_type = std::make_shared<DataTypeUInt8>();

auto null_map = ColumnUInt8::create(

input_rows_count, 1); //if null_map_data==1, the current row should be null

auto* __restrict null_map_data = null_map->get_data().data();

std::vector<ColumnPtr> argument_columns(

argument_size); //use to save nested_column if is nullable column

for (size_t i = 0; i < argument_size; ++i) {

block.get_by_position(filtered_args[i]).column =

block.get_by_position(filtered_args[i])

.column->convert_to_full_column_if_const();

argument_columns[i] = block.get_by_position(filtered_args[i]).column;

if (const auto* nullable =

check_and_get_column<const ColumnNullable>(*argument_columns[i])) {

argument_columns[i] = nullable->get_nested_column_ptr();

}

}

Block temporary_block {

ColumnsWithTypeAndName {block.get_by_position(filtered_args[0]),

{nullptr, std::make_shared<DataTypeUInt8>(), ""}}};

for (size_t i = 0; i < argument_size && remaining_rows; ++i) {

temporary_block.get_by_position(0).column =

block.get_by_position(filtered_args[i]).column;

RETURN_IF_ERROR(

func_is_not_null->execute(context, temporary_block, {0}, 1, input_rows_count));

auto res_column =

(*temporary_block.get_by_position(1).column->convert_to_full_column_if_const())

.mutate();

auto& res_map = assert_cast<ColumnUInt8*, TypeCheckOnRelease::DISABLE>(res_column.get())

->get_data();

auto* __restrict res = res_map.data();

// Here it's SIMD thought the compiler automatically

// true: res[j]==1 && null_map_data[j]==1, false: others

// if true: remaining_rows--; record_idx[j]=column_idx; null_map_data[j]=0, so the current row could fill result

for (size_t j = 0; j < input_rows_count; ++j) {

remaining_rows -= (res[j] & null_map_data[j]);

record_idx[j] += (res[j] & null_map_data[j]) * i;

null_map_data[j] -= (res[j] & null_map_data[j]);

}

if (remaining_rows == 0) {

//check whether all result data from the same column

size_t is_same_column_count = 0;

const auto data = record_idx[0];

for (size_t row = 0; row < input_rows_count; ++row) {

is_same_column_count += (record_idx[row] == data);

}

if (is_same_column_count == input_rows_count) {

if (result_type->is_nullable()) {

block.get_by_position(result).column =

make_nullable(argument_columns[i], false);

} else {

block.get_by_position(result).column = argument_columns[i];

}

return Status::OK();

}

}

if (!is_string_result) {

//if not string type, could check one column firstly,

//and then fill the not null value in result column,

//this method may result in higher CPU cache

RETURN_IF_ERROR(filled_result_column(result_type, result_column,

argument_columns[i], null_map_data,

filled_flags.data(), input_rows_count));

}

}

if (is_string_result) {

//if string type, should according to the record results, fill in result one by one,

for (size_t row = 0; row < input_rows_count; ++row) {

if (null_map_data[row]) { //should be null

result_column->insert_default();

} else {

result_column->insert_from(*argument_columns[record_idx[row]].get(), row);

}

}

}

if (result_type->is_nullable()) {

block.replace_by_position(

result, ColumnNullable::create(std::move(result_column), std::move(null_map)));

} else {

block.replace_by_position(result, std::move(result_column));

}

return Status::OK();

}

template <typename ColumnType>

Status insert_result_data(MutableColumnPtr& result_column, ColumnPtr& argument_column,

const UInt8* __restrict null_map_data, UInt8* __restrict filled_flag,

const size_t input_rows_count) const {

auto* __restrict result_raw_data =

reinterpret_cast<ColumnType*>(result_column.get())->get_data().data();

auto* __restrict column_raw_data =

reinterpret_cast<const ColumnType*>(argument_column.get())->get_data().data();

// Here it's SIMD thought the compiler automatically also

// true: null_map_data[row]==0 && filled_idx[row]==0

// if true, could filled current row data into result column

for (size_t row = 0; row < input_rows_count; ++row) {

result_raw_data[row] +=

(!(null_map_data[row] | filled_flag[row])) * column_raw_data[row];

filled_flag[row] += (!(null_map_data[row] | filled_flag[row]));

}

return Status::OK();

}

Status insert_result_data_bitmap(MutableColumnPtr& result_column, ColumnPtr& argument_column,

const UInt8* __restrict null_map_data,

UInt8* __restrict filled_flag,

const size_t input_rows_count) const {

auto* __restrict result_raw_data =

reinterpret_cast<ColumnBitmap*>(result_column.get())->get_data().data();

auto* __restrict column_raw_data =

reinterpret_cast<const ColumnBitmap*>(argument_column.get())->get_data().data();

// Here it's SIMD thought the compiler automatically also

// true: null_map_data[row]==0 && filled_idx[row]==0

// if true, could filled current row data into result column

for (size_t row = 0; row < input_rows_count; ++row) {

if (!(null_map_data[row] | filled_flag[row])) {

result_raw_data[row] = column_raw_data[row];

}

filled_flag[row] += (!(null_map_data[row] | filled_flag[row]));

}

return Status::OK();

}

[[nodiscard]] Status filled_result_column(const DataTypePtr& data_type,

MutableColumnPtr& result_column,

ColumnPtr& argument_column,

UInt8* __restrict null_map_data,

UInt8* __restrict filled_flag,

const size_t input_rows_count) const {

switch (data_type->get_primitive_type()) {

case PrimitiveType::TYPE_BOOLEAN:

return insert_result_data<ColumnUInt8>(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

case PrimitiveType::TYPE_TINYINT:

return insert_result_data<ColumnInt8>(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

case PrimitiveType::TYPE_SMALLINT:

return insert_result_data<ColumnInt16>(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

case PrimitiveType::TYPE_INT:

return insert_result_data<ColumnInt32>(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

case PrimitiveType::TYPE_BIGINT:

return insert_result_data<ColumnInt64>(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

case PrimitiveType::TYPE_LARGEINT:

return insert_result_data<ColumnInt128>(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

case PrimitiveType::TYPE_FLOAT:

return insert_result_data<ColumnFloat32>(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

case PrimitiveType::TYPE_DOUBLE:

return insert_result_data<ColumnFloat64>(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

case PrimitiveType::TYPE_DECIMAL32:

return insert_result_data<ColumnDecimal32>(

result_column, argument_column, null_map_data, filled_flag, input_rows_count);

case PrimitiveType::TYPE_DECIMAL64:

return insert_result_data<ColumnDecimal64>(

result_column, argument_column, null_map_data, filled_flag, input_rows_count);

case PrimitiveType::TYPE_DECIMAL256:

return insert_result_data<ColumnDecimal256>(

result_column, argument_column, null_map_data, filled_flag, input_rows_count);

case PrimitiveType::TYPE_DECIMALV2:

return insert_result_data<ColumnDecimal128V2>(

result_column, argument_column, null_map_data, filled_flag, input_rows_count);

case PrimitiveType::TYPE_DECIMAL128I:

return insert_result_data<ColumnDecimal128V3>(

result_column, argument_column, null_map_data, filled_flag, input_rows_count);

case PrimitiveType::TYPE_DATETIME:

return insert_result_data<ColumnDateTime>(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

case PrimitiveType::TYPE_DATE:

return insert_result_data<ColumnDate>(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

case PrimitiveType::TYPE_DATEV2:

return insert_result_data<ColumnDateV2>(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

case PrimitiveType::TYPE_DATETIMEV2:

return insert_result_data<ColumnDateTimeV2>(

result_column, argument_column, null_map_data, filled_flag, input_rows_count);

case PrimitiveType::TYPE_BITMAP:

return insert_result_data_bitmap(result_column, argument_column, null_map_data,

filled_flag, input_rows_count);

default:

return Status::NotSupported("argument_type {} not supported", data_type->get_name());

}

}