yiguolei commented on code in PR #14480: URL: https://github.com/apache/doris/pull/14480#discussion_r1028951585
########## be/src/vec/common/hash_table/partitioned_hash_table.h: ########## @@ -0,0 +1,666 @@ +// 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/Common/HashTable/TwoLevelHashTable.h +// and modified by Doris +#pragma once + +#include "vec/common/hash_table/hash_table.h" + +/** Partitioned hash table. + * Represents 16 (or 1ULL << BITS_FOR_SUB_TABLE) small hash tables (sub table count of the first level). + * To determine which one to use, one of the bytes of the hash function is taken. + * + * Usually works a little slower than a simple hash table. + * However, it has advantages in some cases: + * - if you need to merge two hash tables together, then you can easily parallelize it by sub tables; + * - delay during resizes is amortized, since the small hash tables will be resized separately; + * - in theory, resizes are cache-local in a larger range of sizes. + */ + +template <size_t initial_size_degree = 8> +struct PartitionedHashTableGrower : public HashTableGrowerWithPrecalculation<initial_size_degree> { + /// Increase the size of the hash table. + void increase_size() { this->increase_size_degree(this->size_degree() >= 15 ? 1 : 2); } +}; + +template <typename Key, typename Cell, typename Hash, typename Grower, typename Allocator, + typename ImplTable = HashTable<Key, Cell, Hash, Grower, Allocator>, + bool ENABLE_PARTITIONED = false, size_t BITS_FOR_SUB_TABLE = 4> +class PartitionedHashTable : private boost::noncopyable, + protected Hash /// empty base optimization +{ +public: + using Impl = ImplTable; + + using key_type = typename Impl::key_type; + using mapped_type = typename Impl::mapped_type; + using value_type = typename Impl::value_type; + using cell_type = typename Impl::cell_type; + + using LookupResult = typename Impl::LookupResult; + using ConstLookupResult = typename Impl::ConstLookupResult; + +protected: + friend class const_iterator; + friend class iterator; + + using HashValue = size_t; + using Self = PartitionedHashTable; + +private: + static constexpr size_t NUM_LEVEL1_SUB_TABLES = 1ULL << BITS_FOR_SUB_TABLE; + static constexpr size_t MAX_SUB_TABLE = NUM_LEVEL1_SUB_TABLES - 1; + + //factor that will trigger growing the hash table on insert. + static constexpr float MAX_SUB_TABLE_OCCUPANCY_FRACTION = 0.5f; + + static const int PARTITIONED_BUCKET_THRESHOLD = 8388608; + + Impl level0_sub_table; + Impl level1_sub_tables[NUM_LEVEL1_SUB_TABLES]; + + bool _is_partitioned = false; + + // if ENABLE_PARTITIONED, the threshold of bucket count of level0 hash table above + // which the hash table is converted to partioned hash table + int _partitioned_threshold = PARTITIONED_BUCKET_THRESHOLD; + +public: + PartitionedHashTable() { + if constexpr (ENABLE_PARTITIONED) { + level0_sub_table.set_partitioned_threshold(PARTITIONED_BUCKET_THRESHOLD); + } + } + + explicit PartitionedHashTable(size_t size_hint) { + if constexpr (ENABLE_PARTITIONED) { + level0_sub_table.set_partitioned_threshold(PARTITIONED_BUCKET_THRESHOLD); + if (level0_sub_table.check_if_need_partition(size_hint)) { + _is_partitioned = true; + + for (size_t i = 0; i < NUM_LEVEL1_SUB_TABLES; ++i) { + level1_sub_tables[i] = std::move(Impl(size_hint / NUM_LEVEL1_SUB_TABLES)); + } + } else { + level0_sub_table = std::move(Impl(size_hint)); + } + } else { + level0_sub_table = std::move(Impl(size_hint)); + } + } + + PartitionedHashTable(PartitionedHashTable&& rhs) { *this = std::move(rhs); } + + PartitionedHashTable& operator=(PartitionedHashTable&& rhs) { + std::swap(_is_partitioned, rhs._is_partitioned); + std::swap(_partitioned_threshold, rhs._partitioned_threshold); + + level0_sub_table = std::move(rhs.level0_sub_table); + for (size_t i = 0; i < NUM_LEVEL1_SUB_TABLES; ++i) { + level1_sub_tables[i] = std::move(rhs.level1_sub_tables[i]); + } + return *this; + } + + size_t hash(const Key& x) const { return Hash::operator()(x); } + + float get_factor() const { return MAX_SUB_TABLE_OCCUPANCY_FRACTION; } + + bool should_be_shrink(int64_t valid_row) const { + if constexpr (ENABLE_PARTITIONED) { + if (_is_partitioned) { + return false; + } else { + return level0_sub_table.should_be_shrink(valid_row); + } + } else { + return level0_sub_table.should_be_shrink(valid_row); + } + } + + template <typename Func> + void ALWAYS_INLINE for_each_value(Func&& func) { + if constexpr (ENABLE_PARTITIONED) { + if (_is_partitioned) { + for (auto i = 0u; i < NUM_LEVEL1_SUB_TABLES; ++i) { + level1_sub_tables[i].for_each_value(func); + } + } else { + level0_sub_table.for_each_value(func); + } + } else { + level0_sub_table.for_each_value(func); + } + } + + size_t get_size() { + size_t count = 0; + if constexpr (ENABLE_PARTITIONED) { + if (_is_partitioned) { + for (auto i = 0u; i < this->NUM_LEVEL1_SUB_TABLES; ++i) { + for (auto& v : this->level1_sub_tables[i]) { + count += v.get_second().get_row_count(); + } + } + } else { + count = level0_sub_table.get_size(); + } + } else { + count = level0_sub_table.get_size(); + } + return count; + } + + void init_buf_size(size_t reserve_for_num_elements) { + if constexpr (ENABLE_PARTITIONED) { + if (_is_partitioned) { + for (auto& impl : level1_sub_tables) { + impl.init_buf_size(reserve_for_num_elements / NUM_LEVEL1_SUB_TABLES); + } + } else { + if (level0_sub_table.check_if_need_partition(reserve_for_num_elements)) { + level0_sub_table.clear_and_shrink(); + _is_partitioned = true; + + for (size_t i = 0; i < NUM_LEVEL1_SUB_TABLES; ++i) { + level1_sub_tables[i].init_buf_size(reserve_for_num_elements / + NUM_LEVEL1_SUB_TABLES); + } + } else { + level0_sub_table.init_buf_size(reserve_for_num_elements); + } + } + } else { + level0_sub_table.init_buf_size(reserve_for_num_elements); + } + } + + void delete_zero_key(Key key) { + if constexpr (ENABLE_PARTITIONED) { Review Comment: ENABLE_PARTITIONED this template variable is useless. -- This is an automated message from the Apache Git Service. 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