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223 行
5.1 KiB
223 行
5.1 KiB
#pragma once
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#include "fsized_map.h"
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#include <chrono>
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struct metadata_t{
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bitops::regulated<uint64_t> record_cnt;
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bitops::regulated<uint64_t> page_cnt;
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bitops::regulated<uint64_t> delete_cnt;
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bitops::regulated<uint64_t> last_page;
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bitops::regulated<uint64_t> last_delete;
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};
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class database {
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database(){}
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public:
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mmap_array<std::pair<bitops::regulated<uint64_t>, record>> records;
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mmap_array<db_page> pages;
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mmap_array<metadata_t> metadata;
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mmap_array<size_t> delete_table;
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database(
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const std::string& records,
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const std::string& pages,
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const std::string& deletions,
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const std::string& meta,
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const size_t& record_cnt = 4096,
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const size_t& page_cnt = 4096,
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const size_t& delete_cnt = 512
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)
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: records{record_cnt, records}
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, pages{page_cnt, pages}
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, metadata{(size_t)1, meta}
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, delete_table{delete_cnt, deletions}
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{}
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static database&& create(const std::string dir, size_t page_nb) {
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database ret{
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dir+"records",
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dir+"pages",
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dir+"deleted",
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dir+"meta",
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page_nb+page_nb/2,
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page_nb,
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page_nb/8
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};
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for(auto& n : ret.records)
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{
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n.second.timestamp = 0;
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n.second.offset = 0;
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}
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for(auto& n : ret.delete_table)
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{
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n = std::numeric_limits<size_t>::max();
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}
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(*ret.metadata).last_page = 0;
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(*ret.metadata).last_delete = 0;
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(*ret.metadata).record_cnt = page_nb+page_nb/2;
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(*ret.metadata).page_cnt = page_nb;
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(*ret.metadata).delete_cnt = page_nb/8;
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wreturn-local-addr"
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return std::move(ret);
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#pragma GCC diagnostic pop
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}
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static database&& open(const std::string dir) {
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mmap_array<metadata_t> tmp{(size_t)1, dir+"meta"};
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database ret{
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dir+"records",
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dir+"pages",
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dir+"deleted",
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dir+"meta",
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(*tmp).record_cnt,
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(*tmp).page_cnt,
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(*tmp).delete_cnt
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};
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tmp.clear();
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ret.records.enforce_caching();
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wreturn-local-addr"
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return std::move(ret);
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#pragma GCC diagnostic pop
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}
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void write(const record_identifier& target, const db_page& value){
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uint64_t page = std::numeric_limits<uint64_t>::max();;
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size_t off = std::numeric_limits<size_t>::max();
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if(metadata[0].last_delete>0)
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{
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off = (*metadata).last_delete;
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page = delete_table[off-1];
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} else {
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page = (*metadata).last_page;
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if(page>=pages.size()) {
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throw std::runtime_error("PAGE STARVATION! MUST EXIT NOW");
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}
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}
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if(page == std::numeric_limits<uint64_t>::max())
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{
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throw std::runtime_error("PAGE ERROR! MUST EXIT NOW");
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}
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pages[page] = value;
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uint64_t hashed = std::hash<record_identifier>{}(target);
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uint64_t hashed_roll = hashed;
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bool succeed = false;
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uint64_t ts = std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::system_clock::now().time_since_epoch()).count();
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std::pair<bitops::regulated<uint64_t>,record> tmp{0, record{}};
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tmp.first = hashed;
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tmp.second.record_head.split = target;
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tmp.second.timestamp = ts;
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tmp.second.offset = page;
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do{
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uint64_t pos = hashed_roll % records.size();
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switch (static_cast<uint64_t>(records[pos].second.timestamp)) {
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case 0:
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[[fallthrough]];
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case std::numeric_limits<uint64_t>::max():
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records[pos] = tmp;
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succeed = true;
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break;
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default:
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break;
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}
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hashed_roll++;
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}while(!succeed);
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if(off != std::numeric_limits<size_t>::max())
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{
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(*metadata).last_delete += -1;
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delete_table[off] = std::numeric_limits<size_t>::max();
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} else {
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(*metadata).last_page += (size_t)1;
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}
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}
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std::pair<uint64_t, db_page> read(const record_identifier& target) {
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std::pair<uint64_t, db_page> ret;
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ret.first = 0;
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ret.second.fill(0);
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uint64_t hashed = std::hash<record_identifier>{}(target);
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uint64_t hashed_roll = hashed;
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do{
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uint64_t pos = hashed_roll % records.size();
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auto& value = records[pos].second;
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switch (static_cast<uint64_t>(value.timestamp)) {
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case 0:
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return ret;
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case std::numeric_limits<uint64_t>::max():
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break;
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default:
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if(records[pos].first == hashed)
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if(std::hash<record_identifier>{}(value.record_head.split) == hashed)
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{
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if(ret.first<value.timestamp)
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{
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ret.first = value.timestamp;
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ret.second = pages[value.offset];
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}
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break;
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}
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}
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hashed_roll++;
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}while(true);
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return ret;
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}
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void remove(const record_identifier& target) {
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uint64_t hashed = std::hash<record_identifier>{}(target);
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uint64_t hashed_roll = hashed;
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do{
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uint64_t pos = hashed_roll % records.size();
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auto& value = records[pos].second;
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switch (static_cast<uint64_t>(value.timestamp)) {
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case 0:
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return;
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case std::numeric_limits<uint64_t>::max():
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break;
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default:
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if(records[pos].first == hashed)
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if(std::hash<record_identifier>{}(value.record_head.split) == hashed)
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{
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value.timestamp = std::numeric_limits<uint64_t>::max();
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(*metadata).last_delete+=1;
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delete_table[(*metadata).last_delete-1] = value.offset;
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value.offset = 0;
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break;
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}
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}
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hashed_roll++;
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}while(true); // return only happens on hitting a case 0
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}
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void rollback(const record_identifier&) {
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}
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};
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