daju233 commented on code in PR #60192: URL: https://github.com/apache/doris/pull/60192#discussion_r2786329709
########## be/src/vec/functions/array/function_array_combinations.cpp: ########## @@ -0,0 +1,184 @@ +// 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. + +#include "common/compiler_util.h" +#include "common/logging.h" +#include "common/status.h" +#include "runtime/define_primitive_type.h" +#include "runtime/primitive_type.h" +#include "vec/columns/column.h" +#include "vec/columns/column_array.h" +#include "vec/columns/column_const.h" +#include "vec/common/assert_cast.h" +#include "vec/core/field.h" +#include "vec/core/types.h" +#include "vec/data_types/data_type.h" +#include "vec/data_types/data_type_array.h" +#include "vec/data_types/data_type_decimal.h" +#include "vec/data_types/data_type_nullable.h" +#include "vec/functions/function.h" +#include "vec/functions/function_helpers.h" +#include "vec/functions/simple_function_factory.h" + +namespace doris::vectorized { +// array_combinations([1, 2, 3],2) -> [[1,2], [1,3], [2,3]] +// array_combinations([1, NULL, 3, NULL, 5]，4) -> [[1,NULL,3,NULL], [1,NULL,3,5], [NULL,3,NULL,5]] + +class FunctionArrayCombinations : public IFunction { +public: + static constexpr auto name = "array_combinations"; + static FunctionPtr create() { return std::make_shared<FunctionArrayCombinations>(); } + bool is_variadic() const override { return false; } + String get_name() const override { return name; } + + size_t get_number_of_arguments() const override { return 2; } + + DataTypePtr get_return_type_impl(const DataTypes& arguments) const override { + const auto* array_type = assert_cast<const DataTypeArray*>(arguments[0].get()); + auto elem_t = make_nullable(array_type->get_nested_type()); + auto res = std::make_shared<DataTypeArray>( + make_nullable(std::make_shared<DataTypeArray>(elem_t))); + return res; + } + + Status execute_impl(FunctionContext* context, Block& block, const ColumnNumbers& arguments, + uint32_t result, size_t input_rows_count) const override { + auto array = block.get_by_position(arguments[0]).column; + ColumnPtr num = block.get_by_position(arguments[1]).column; + + Int64 combination_length = num->get_int(0); + + if (combination_length > MAX_COMBINATION_LENGTH || combination_length < 0) { + return Status::RuntimeError( + fmt::format("execute failed, function {}'s second argument must be bigger than " + "0 and not bigger than 5", + get_name())); + } + + ColumnPtr res; + const auto* src_arr = assert_cast<const ColumnArray*>(remove_nullable(array).get()); + const auto& offsets = + assert_cast<const ColumnArray::ColumnOffsets&>(src_arr->get_offsets_column()); + Status status = vector_const(src_arr, input_rows_count, res, offsets, combination_length); + if (!status.ok()) { + return status; + } + block.replace_by_position(result, std::move(res)); + return status; + } + + ColumnNumbers get_arguments_that_are_always_constant() const override { return {1}; } + +private: + static const size_t MAX_COMBINATION_LENGTH = 5; + static const size_t MAX_COMBINATION_COUNT = 100000; + + // Then combinationCount(n, k) = combinationCount(n-1, k-1) * n/k (https://en.wikipedia.org/wiki/Combination#Number_of_k-combinations) + // The formula is recursive. Here, instead of starting with k=combinationCount, n=arrayLength and recursing, + // we start with k=0 n=(arrayLength-combinationLength) and proceed "bottom up". + size_t _combination_count(size_t array_length, size_t combination_length) const { + size_t combinations = 1; + + for (int i = 1; i <= combination_length; i++) { + combinations = combinations * (array_length - combination_length + i) / i; + } + + return combinations; + } + + ALWAYS_INLINE std::vector<size_t> _first_combination(Int64 combination_length, + size_t length) const { + std::vector<size_t> comb(combination_length + 1); + for (size_t i = 0; i < static_cast<size_t>(combination_length); ++i) { + comb[i] = i; + } + comb[combination_length] = length; + return comb; + } + + // generate next combination + bool _next_combination(std::vector<size_t>& comb, Int64 combination_length) const { + for (size_t i = 0; i < static_cast<size_t>(combination_length); ++i) { + if (comb[i] + 1 < comb[i + 1]) { + ++comb[i]; + for (size_t j = 0; j < i; ++j) { + comb[j] = j; + } + return true; + } + } + return false; + } + + Status vector_const(const ColumnArray* nested_src_column_ptr, size_t input_rows_count, + ColumnPtr& res, const ColumnArray::ColumnOffsets& offsets, + Int64 combination_length) const { Review Comment: why should I do that? -- This is an automated message from the Apache Git Service. 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