// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements. See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership. The ASF licenses this file

// to you under the Apache License, Version 2.0 (the

// "License"); you may not use this file except in compliance

// with the License. You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing,

// software distributed under the License is distributed on an

// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

// KIND, either express or implied. See the License for the

// specific language governing permissions and limitations

// under the License.

// This file is copied from

// https://github.com/ClickHouse/ClickHouse/blob/master/src/Functions/Ifnull.h

// and modified by Doris

#pragma once

#include <stddef.h>

#include <algorithm>

#include <boost/iterator/iterator_facade.hpp>

#include <memory>

#include "common/status.h"

#include "core/block/block.h"

#include "core/block/column_numbers.h"

#include "core/block/column_with_type_and_name.h"

#include "core/block/columns_with_type_and_name.h"

#include "core/column/column.h"

#include "core/column/column_nullable.h"

#include "core/data_type/data_type.h"

#include "core/data_type/data_type_nullable.h"

#include "core/data_type/data_type_number.h"

#include "core/types.h"

#include "exprs/aggregate/aggregate_function.h"

#include "exprs/function/function.h"

#include "exprs/function/simple_function_factory.h"

#include "runtime/runtime_state.h"

namespace doris {

class FunctionContext;

} // namespace doris

namespace doris {

class FunctionIfNull : public IFunction {

public:

static constexpr auto name = "ifnull";

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

String get_name() const override { return name; }

size_t get_number_of_arguments() const override { return 2; }

// be compatible with fe code

/*

if (fn.functionName().equalsIgnoreCase("ifnull") || fn.functionName().equalsIgnoreCase("nvl")) {

Preconditions.checkState(children.size() == 2);

if (children.get(0).isNullable()) {

return children.get(1).isNullable();

}

return false;

}

*/

DataTypePtr get_return_type_impl(const DataTypes& arguments) const override {

if (arguments[0]->is_nullable()) {

return arguments[1];

}

return arguments[0];

}

bool use_default_implementation_for_nulls() const override { return false; }

// ifnull(col_left, col_right) == if(isnull(col_left), col_right, col_left)

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

uint32_t result, size_t input_rows_count) const override {

ColumnWithTypeAndName& col_left = block.get_by_position(arguments[0]);

if (col_left.column->only_null()) {

// Here we need to use convert_to_full_column_if_const because only_null() is a runtime function.

// If the second parameter is constant, it will cause the execution to rely on runtime information to determine whether it is constant.

block.get_by_position(result).column =

block.get_by_position(arguments[1]).column->convert_to_full_column_if_const();

return Status::OK();

}

ColumnWithTypeAndName null_column_arg0 {nullptr, std::make_shared<DataTypeUInt8>(), ""};

ColumnWithTypeAndName nested_column_arg0 {nullptr, col_left.type, ""};

col_left.column = col_left.column->convert_to_full_column_if_const();

/// implement isnull(col_left) logic

if (auto* nullable = check_and_get_column<ColumnNullable>(*col_left.column)) {

null_column_arg0.column = nullable->get_null_map_column_ptr();

nested_column_arg0.column = nullable->get_nested_column_ptr();

nested_column_arg0.type =

reinterpret_cast<const DataTypeNullable*>(nested_column_arg0.type.get())

->get_nested_type();

} else {

block.get_by_position(result).column = col_left.column;

return Status::OK();

}

const ColumnsWithTypeAndName if_columns {

null_column_arg0, block.get_by_position(arguments[1]), nested_column_arg0};

// see get_return_type_impl

// if result is nullable, means both then and else column are nullable, we use original col_left to keep nullable info

// if result is not nullable, means both then and else column are not nullable, we use nested_column_arg0 to remove nullable info

bool result_nullable = block.get_by_position(result).type->is_nullable();

Block temporary_block({

null_column_arg0,

block.get_by_position(arguments[1]),

result_nullable

? col_left

: nested_column_arg0, // if result is nullable, we need pass the original col_left else pass nested_column_arg0

block.get_by_position(result),

});

auto func_if = SimpleFunctionFactory::instance().get_function(

"if", if_columns, block.get_by_position(result).type, {});

RETURN_IF_ERROR(func_if->execute(context, temporary_block, {0, 1, 2}, 3, input_rows_count));

block.get_by_position(result).column = temporary_block.get_by_position(3).column;

return Status::OK();

}

};

} // namespace doris