25'ten fazla konu seçemezsiniz
Konular bir harf veya rakamla başlamalı, kısa çizgiler ('-') içerebilir ve en fazla 35 karakter uzunluğunda olabilir.
72 satır
1.5 KiB
72 satır
1.5 KiB
#include "leveldb/db.h"
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#include "leveldb/filter_policy.h"
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#include <iostream>
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#include <cstdlib>
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#include <ctime>
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using namespace leveldb;
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constexpr int value_size = 2048;
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constexpr int data_size = 256 << 20;
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// 3. 数据管理（Manifest/创建/恢复数据库）
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Status OpenDB(std::string dbName, DB **db) {
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Options options;
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options.create_if_missing = true;
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options.filter_policy = NewBloomFilterPolicy(10);
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return DB::Open(options, dbName, db);
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}
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// 1. 存储（数据结构与写入）
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// 4. 数据合并（Compaction）
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void InsertData(DB *db) {
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WriteOptions writeOptions;
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int key_num = data_size / value_size;
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srand(0);
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for (int i = 0; i < key_num; i++) {
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int key_ = rand() % key_num+1;
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std::string key = std::to_string(key_);
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std::string value(value_size, 'a');
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db->Put(writeOptions, key, value);
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}
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}
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// 2. 数据访问（如何读数据）
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void GetData(DB *db, int size = (1 << 30)) {
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ReadOptions readOptions;
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int key_num = data_size / value_size;
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// 点查
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srand(0);
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for (int i = 0; i < 100; i++) {
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int key_ = rand() % key_num+1;
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std::string key = std::to_string(key_);
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std::string value;
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db->Get(readOptions, key, &value);
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std::cout << value << std::endl;
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}
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// 范围查询
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Iterator *iter = db->NewIterator(readOptions);
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iter->SeekToFirst();
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while (iter->Valid()) {
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iter->Next();
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}
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delete iter;
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}
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int main() {
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DB *db;
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if(OpenDB("testdb", &db).ok()) {
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InsertData(db);
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delete db;
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}
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if(OpenDB("testdb", &db).ok()) {
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GetData(db);
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delete db;
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}
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return 0;
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}
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