kangpinghuang commented on a change in pull request #1572: Add new format short key index URL: https://github.com/apache/incubator-doris/pull/1572#discussion_r310024330
########## File path: be/src/olap/short_key_index.h ########## @@ -0,0 +1,197 @@ +// 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. + +#pragma once + +#include <cstdint> +#include <iterator> +#include <string> +#include <vector> + +#include "common/status.h" +#include "gen_cpp/segment_v2.pb.h" +#include "util/faststring.h" +#include "util/slice.h" + +namespace doris { + +// Used to encode a segment short key indices to binary format. This version +// only accepts binary key, client should assure that input key is sorted, +// otherwise error could happens. This builder would arrange data in following +// format. +// index = encoded_keys + encoded_offsets + footer + footer_size + checksum +// encoded_keys = binary_key + [, ...] +// encoded_offsets = encoded_offset + [, ...] +// encoded_offset = variant32 +// footer = ShortKeyFooterPB +// footer_size = fixed32 +// checksum = fixed32 +// Usage: +// ShortKeyIndexBuilder builder(segment_id, num_rows_per_block); +// builder.add_item(key1); +// ... +// builder.add_item(keyN); +// builder.finalize(segment_size, num_rows, &slices); +// TODO(zc): +// 1. If this can leverage binary page to save key and offset data +// 2. Extending this to save in a BTree like struct, which can index full key +// more than short key +class ShortKeyIndexBuilder { +public: + ShortKeyIndexBuilder(uint32_t segment_id, + uint32_t num_rows_per_block) { + _footer.set_segment_id(segment_id); + _footer.set_num_rows_per_block(num_rows_per_block); + } + + Status add_item(const Slice& key); + + Status finalize(uint32_t segment_size, uint32_t num_rows, std::vector<Slice>* slices); + +private: + segment_v2::ShortKeyFooterPB _footer; + + faststring _key_buf; + faststring _offset_buf; + std::string _footer_buf; + std::vector<uint32_t> _offsets; +}; + +class ShortKeyIndexDecoder; + +// An Iterator to iterate one short key index. +// Client can use this class to iterator all items +// item in this index. +class ShortKeyIndexIterator { +public: + using iterator_category = std::random_access_iterator_tag; + using value_type = Slice; + using pointer = Slice*; + using reference = Slice&; + using difference_type = ssize_t; + + ShortKeyIndexIterator(const ShortKeyIndexDecoder* decoder, uint32_t ordinal = 0) + : _decoder(decoder), _ordinal(ordinal) { } + + ShortKeyIndexIterator& operator-=(ssize_t step) { + _ordinal -= step; + return *this; + } + + ShortKeyIndexIterator& operator+=(ssize_t step) { + _ordinal += step; + return *this; + } + + ShortKeyIndexIterator& operator++() { + _ordinal++; + return *this; + } + + bool operator!=(const ShortKeyIndexIterator& other) { + return _ordinal != other._ordinal || _decoder != other._decoder; + } + + bool operator==(const ShortKeyIndexIterator& other) { + return _ordinal == other._ordinal && _decoder == other._decoder; + } + + ssize_t operator-(const ShortKeyIndexIterator& other) const { + return _ordinal - other._ordinal; + } + + inline bool valid() const; + + Slice operator*() const; + + ssize_t ordinal() const { return _ordinal; } + +private: + const ShortKeyIndexDecoder* _decoder; + ssize_t _ordinal; +}; + +// Used to decode short key to header and encoded index data. +// Usage: +// MemIndex index; +// ShortKeyIndexDecoder decoder(slice) +// decoder.parse(); +// auto iter = decoder.lower_bound(key); +class ShortKeyIndexDecoder { +public: + // Client should assure that data is available when this class + // is used. + ShortKeyIndexDecoder(const Slice& data) : _data(data) { } + + Status parse(); + + ShortKeyIndexIterator begin() const { return {this, 0}; } + ShortKeyIndexIterator end() const { return {this, num_items()}; } + + // lower_bound will return a iterator which locates the first item + // equal with or larger than given key. + // NOTE: This function holds that without common prefix key, the one + // who has more length it the bigger one. Two key is the same only + // when their length are equal + ShortKeyIndexIterator lower_bound(const Slice& key) const { + return seek<true>(key); + } + + // Return the iterator which locates the first item larger than the + // input key. + ShortKeyIndexIterator upper_bound(const Slice& key) const { + return seek<false>(key); + } + + uint32_t num_items() const { return _footer.num_items(); } + + Slice key(ssize_t ordinal) const { + DCHECK(ordinal >= 0 && ordinal < num_items()); + return {_key_data.data + _offsets[ordinal], _offsets[ordinal + 1] - _offsets[ordinal]}; + } + +private: + template<bool lower_bound> + ShortKeyIndexIterator seek(const Slice& key) const { + auto comparator = [this] (const Slice& lhs, const Slice& rhs) { + return lhs.compare(rhs) < 0; + }; + if (lower_bound) { + return std::lower_bound(begin(), end(), key, comparator); + } else { + return std::upper_bound(begin(), end(), key, comparator); + } + } + +private: + Slice _data; + + // All following fields are only valid after pares has been executed successfully Review comment: ```suggestion // All following fields are only valid after parse has been executed successfully ``` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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