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<a href="/2022/02/14/061-tidb-binlog-mysql/" class="post-title-link" itemprop="url">使用 TiDB Binlog 同步数据到 MySQL 步骤</a>
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<h1 id="使用-TiDB-Binlog-同步数据到-MySQL-步骤"><a href="#使用-TiDB-Binlog-同步数据到-MySQL-步骤" class="headerlink" title="使用 TiDB Binlog 同步数据到 MySQL 步骤"></a>使用 TiDB Binlog 同步数据到 MySQL 步骤</h1><p>本文档适用于 TiDB 集群已经搭建完成并且已有部分数据在集群中，需要搭建 TiDB Binlog 将 TiDB 中数据同步到 MySQL 的情况 。</p>
<p><strong>说明：</strong></p>
<ul>
<li>$ 符号表示命令需要在服务器命令行中执行</li>
<li>${xxx} 表示需要替换成实际对应的内容</li>
</ul>
<h2 id="步骤一、扩容-pump-节点"><a href="#步骤一、扩容-pump-节点" class="headerlink" title="步骤一、扩容 pump 节点"></a>步骤一、扩容 pump 节点</h2><ol>
<li>准备扩容 pump 节点的拓扑文件</li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> cat scale-pump.yaml</span><br><span class="line">pump_servers:</span><br><span class="line"> host: 10.55.12.31</span><br><span class="line"> host: 10.55.12.32</span><br><span class="line"> host: 10.55.12.33</span><br></pre></td></tr></table></figure>
<ol start="2">
<li>执行扩容命令</li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> tiup cluster scale-out ${cluster_name} ./scale-pump.yaml -uroot -p</span><br></pre></td></tr></table></figure>
<ol start="3">
<li>修改 TiDB 集群，开启 Binlog </li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> tiup cluster edit-config ${cluster_name}</span><br><span class="line">在 server_config 部分添加对应的配置</span><br><span class="line">server_configs:</span><br><span class="line"> tidb:</span><br><span class="line"> binlog.enable: true</span><br><span class="line"> binlog.ignore-error: true</span><br></pre></td></tr></table></figure>
<ol start="4">
<li>滚动重启 tidb-server 节点开始 binlog</li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> tiup cluster reload ${cluster_name} -R tidb</span><br></pre></td></tr></table></figure>
<ol start="5">
<li>查看集群状态</li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> tiup cluster display ${cluster_name}</span><br></pre></td></tr></table></figure>
<h2 id="步骤二、全量数据迁移"><a href="#步骤二、全量数据迁移" class="headerlink" title="步骤二、全量数据迁移"></a>步骤二、全量数据迁移</h2><ol>
<li>使用 mydumper 全量初始化导出</li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> wget http://download.pingcap.org/tidb-enterprise-tools-latest-linux-amd64.tar.gz</span><br><span class="line"><span class="meta">$</span> tar -xzf tidb-enterprise-tools-latest-linux-amd64.tar.gz && cd tidb-enterprise-tools-latest-linux-amd64</span><br><span class="line"><span class="meta">$</span> ./bin/mydumper -h ${source ip} -P 4000 -u root -t 16 -F 64 --skip-tz-utc -o ./tmp/all_backup</span><br></pre></td></tr></table></figure>
<ol start="2">
<li>获取 initial_commit_ts</li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> cat /tmp/all_backup/metadata</span><br><span class="line">Started dump at: 2019-12-13 15:16:44</span><br><span class="line">SHOW MASTER STATUS:</span><br><span class="line"> Log: tidb-binlog</span><br><span class="line"> Pos: 413196983854432259</span><br><span class="line"> GTID:</span><br><span class="line">Finished dump at: 2019-12-13 15:16:48</span><br></pre></td></tr></table></figure>
<p>Pos 413196983854432259 即为备份的 tso 时刻点值，后续 Binlog 增量同步时需要从这个时间点开始同步</p>
<ol start="3">
<li>备份数据复制到 MySQL 节点并使用 loader 将全备数据导入到目标库中</li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> ./bin/loader -h ${target ip} -u root -P 3306 -t 32 -d /tmp/all_backup</span><br></pre></td></tr></table></figure>
<h2 id="步骤三、扩容-drainer-节点"><a href="#步骤三、扩容-drainer-节点" class="headerlink" title="步骤三、扩容 drainer 节点"></a>步骤三、扩容 drainer 节点</h2><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">1. 准备扩容 drainer 节点的拓扑文件</span><br><span class="line"><span class="meta">$</span> cat scale-drainer.yaml</span><br><span class="line">drainer_servers:</span><br><span class="line"> - host: 10.0.1.12</span><br><span class="line"> # commit_ts 填写 mydumper 备份文件中 metadata 记录的 tso 号信息</span><br><span class="line"> commit_ts: 413196983854432259</span><br><span class="line"> config:</span><br><span class="line"> syncer.db-type: "mysql"</span><br><span class="line"> syncer.to.host: "10.0.1.12"</span><br><span class="line"> syncer.to.user: "root"</span><br><span class="line"> syncer.to.password: ""</span><br><span class="line"> syncer.to.port: 3306</span><br><span class="line"> syncer.relay.log-dir: "/dir/to/save/log"</span><br><span class="line"> syncer.relay.max-file-size: 10485760</span><br></pre></td></tr></table></figure>
<ol start="2">
<li>通过 tiup 执行扩容命令</li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> tiup cluster scale-out ${cluster_name} ./scale-drainer.yaml -uroot -p</span><br></pre></td></tr></table></figure>
<ol start="3">
<li>查看集群节点状态</li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> tiup cluster display ${cluster_name}</span><br></pre></td></tr></table></figure>
<h2 id="步骤四、检查增量数据同步情况"><a href="#步骤四、检查增量数据同步情况" class="headerlink" title="步骤四、检查增量数据同步情况"></a>步骤四、检查增量数据同步情况</h2><p>在上游 TiDB 执行一些变更操作，在下游 MySQL 中查询验证数据是否正常同步。</p>
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<h1 id="使用-Github-Action-替换-Travis-自动发布-Hexo-博客"><a href="#使用-Github-Action-替换-Travis-自动发布-Hexo-博客" class="headerlink" title="使用 Github Action 替换 Travis 自动发布 Hexo 博客"></a>使用 Github Action 替换 Travis 自动发布 Hexo 博客</h1><p>之前通过 Hexo + Github Pages 的模式搭建了这个博客，并且通过 Travis 自动集成发布我更新的博客文章。但是从 2021 年 12 月份开始 Travis CI 不再免费为开源项目提供持续集成的托管服务了。也是因为我好久没写博客了，导致这个问题直到最近才被发现。寻找替代方案，找了一圈发现 Github 自己提供了 Github Actions 的持续集成服务。那就折腾折腾替换成 Github Actions 来发布博客。</p>
<h2 id="准备工作"><a href="#准备工作" class="headerlink" title="准备工作"></a>准备工作</h2><h2 id="介绍"><a href="#介绍" class="headerlink" title="介绍"></a>介绍</h2><p>我的博客项目地址是：<a href="https://github.com/Win-Man/win-man.github.io" target="_blank" rel="noopener">https://github.com/Win-Man/win-man.github.io</a> 。repo 中分了两个分支，一个 master 分支和一个 dev 分支。dev 分支负责存放原始的 hexo 文件，master 分支负责存放 hexo generate 生成的 html 文件，然后通过 <a href="https://win-man.github.io/" target="_blank" rel="noopener">https://win-man.github.io/</a> 这个网址访问到的就是 master 分支上的 html 文件了。</p>
<p>之前 Travis CI 持续集成服务中是会监测 dev 分支的更新，每当我有将提交 push 到 dev 分支上的时候，会触发 Travis CI 的持续集成服务，基于 dev 分支的内容自动更新 master 分支。所以想用 Github Actions 替换 Travis CI 也是类似的思路：</p>
<ol>
<li>监测到 dev 分支有更新</li>
<li>基于 dev 分支内容执行 hexo deploy </li>
</ol>
<h2 id="步骤"><a href="#步骤" class="headerlink" title="步骤"></a>步骤</h2><h3 id="生成秘钥"><a href="#生成秘钥" class="headerlink" title="生成秘钥"></a>生成秘钥</h3><p>这一步是为了让 Github Actions 有权限将更新 push 到 repo 。</p>
<ol>
<li>创建一个新的 SSH 秘钥</li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">ssh-keygen -f hexo-deploy-key</span><br></pre></td></tr></table></figure>
<p>会生成 hexo-deploy-key 和 hexo-deploy-key.pub 两个文件</p>
<ol start="2">
<li>在 win-man.github.io 这个项目添加 Secrets</li>
</ol>
<p>添加 hexo-deploy-key 的内容作为 Secrets<br><img src="https://raw.githubusercontent.com/Win-Man/pic-storage/master/img/20220208200006.png" alt="add secrets"></p>
<ol start="3">
<li>在 win-man.github.io 这个项目添加 Deploy key</li>
</ol>
<p>添加 hexo-deploy-key.pub 的内容作为 Deploy key<br><img src="https://raw.githubusercontent.com/Win-Man/pic-storage/master/img/20220208200219.png" alt="add deploy key"></p>
<h3 id="配置-Github-Action"><a href="#配置-Github-Action" class="headerlink" title="配置 Github Action"></a>配置 Github Action</h3><ol>
<li>切换到 dev 分支下，然后创建 workflows 目录, 并配置 main.yaml 文件</li>
</ol>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">mkdir -p .github/workflows/</span><br><span class="line">touch .github/workflows/main.yaml</span><br></pre></td></tr></table></figure>
<ol start="2">
<li>填写配置文件</li>
</ol>
<p>配置文件内容如下:</p>
<figure class="highlight yaml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br></pre></td><td class="code"><pre><span class="line"><span class="attr">name:</span> <span class="string">hexo-deploy</span></span><br><span class="line"><span class="attr">on:</span></span><br><span class="line"> <span class="attr">push:</span></span><br><span class="line"> <span class="attr">branches:</span> <span class="string">[</span> <span class="string">dev</span> <span class="string">]</span></span><br><span class="line"> <span class="attr">pull_request:</span></span><br><span class="line"> <span class="attr">branches:</span> <span class="string">[</span> <span class="string">dev</span> <span class="string">]</span></span><br><span class="line"></span><br><span class="line"> <span class="attr">workflow_dispatch:</span></span><br><span class="line"></span><br><span class="line"><span class="comment"># A workflow run is made up of one or more jobs that can run sequentially or in parallel</span></span><br><span class="line"><span class="attr">jobs:</span></span><br><span class="line"> <span class="comment"># This workflow contains a single job called "build"</span></span><br><span class="line"> <span class="attr">build:</span></span><br><span class="line"> <span class="comment"># The type of runner that the job will run on</span></span><br><span class="line"> <span class="attr">runs-on:</span> <span class="string">ubuntu-latest</span></span><br><span class="line"></span><br><span class="line"> <span class="comment"># Steps represent a sequence of tasks that will be executed as part of the job</span></span><br><span class="line"> <span class="attr">steps:</span></span><br><span class="line"> <span class="comment"># Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it</span></span><br><span class="line"> <span class="bullet">-</span> <span class="attr">name:</span> <span class="string">Checkout</span> <span class="string">dev</span> <span class="string">branch</span></span><br><span class="line"> <span class="attr">uses:</span> <span class="string">actions/checkout@v2</span></span><br><span class="line"> <span class="attr">with:</span></span><br><span class="line"> <span class="attr">ref:</span> <span class="string">dev</span></span><br><span class="line"> <span class="bullet">-</span> <span class="attr">name:</span> <span class="string">Config</span> <span class="string">node.js</span></span><br><span class="line"> <span class="attr">uses:</span> <span class="string">actions/setup-node@v2</span></span><br><span class="line"> <span class="attr">with:</span></span><br><span class="line"> <span class="attr">node-version:</span> <span class="string">'13'</span></span><br><span class="line"> <span class="attr">cache:</span> <span class="string">'npm'</span></span><br><span class="line"> <span class="bullet">-</span> <span class="attr">name:</span> <span class="string">Install</span> <span class="string">hexo</span></span><br><span class="line"> <span class="attr">env:</span></span><br><span class="line"> <span class="attr">ACTION_DEPLOY_KEY:</span> <span class="string">${{</span> <span class="string">secrets.HEXO_DEPLOY_SECRET</span> <span class="string">}}</span></span><br><span class="line"> <span class="attr">run:</span> <span class="string">|</span></span><br><span class="line"> <span class="string">mkdir</span> <span class="string">-p</span> <span class="string">~/.ssh/</span></span><br><span class="line"> <span class="string">echo</span> <span class="string">"$ACTION_DEPLOY_KEY"</span> <span class="string">></span> <span class="string">~/.ssh/id_rsa</span></span><br><span class="line"> <span class="string">chmod</span> <span class="number">600</span> <span class="string">~/.ssh/id_rsa</span></span><br><span class="line"> <span class="string">ssh-keyscan</span> <span class="string">github.com</span> <span class="string">>></span> <span class="string">~/.ssh/known_hosts</span></span><br><span class="line"> <span class="string">git</span> <span class="string">config</span> <span class="string">--global</span> <span class="string">user.name</span> <span class="string">"Win-Man"</span></span><br><span class="line"> <span class="string">git</span> <span class="string">config</span> <span class="string">--global</span> <span class="string">user.email</span> <span class="number">825895587</span><span class="string">@qq.com</span></span><br><span class="line"> <span class="string">npm</span> <span class="string">install</span> <span class="string">hexo-cli</span> <span class="string">-g</span></span><br><span class="line"> <span class="string">npm</span> <span class="string">install</span></span><br><span class="line"> <span class="bullet">-</span> <span class="attr">name:</span> <span class="string">Generate</span> <span class="string">and</span> <span class="string">deploy</span></span><br><span class="line"> <span class="attr">run:</span> <span class="string">|</span></span><br><span class="line"> <span class="string">hexo</span> <span class="string">clean</span></span><br><span class="line"> <span class="string">hexo</span> <span class="string">deploy</span></span><br></pre></td></tr></table></figure>
<ol start="3">
<li><p>提交 Github Actions 配置</p>
</li>
<li><p>查看 Github Actions 并测试</p>
</li>
</ol>
<p>每当 dev 分支有代码更新的时候，就会触发 Github Actions 的工作流自动发布博客了。</p>
<p><img src="https://raw.githubusercontent.com/Win-Man/pic-storage/master/img/20220208200903.png" alt="actions"></p>
<h2 id="问题"><a href="#问题" class="headerlink" title="问题"></a>问题</h2><h3 id="node-version-错误导致生成-html-为空"><a href="#node-version-错误导致生成-html-为空" class="headerlink" title="node version 错误导致生成 html 为空"></a>node version 错误导致生成 html 为空</h3><h4 id="问题描述"><a href="#问题描述" class="headerlink" title="问题描述"></a>问题描述</h4><p>Github Actions job 正常触发也正常运行了，没有报错，但是访问 <a href="https://win-man.github.io/" target="_blank" rel="noopener">https://win-man.github.io/</a> 这个网址却是一篇空白。检查 master 分支上的 html 文件发现每篇文章的 html 文件是生成了，但是里面的内容是空的。</p>
<h4 id="问题原因"><a href="#问题原因" class="headerlink" title="问题原因"></a>问题原因</h4><p>nodejs 版本太高，hexo 不支持。</p>
<h4 id="解决方案"><a href="#解决方案" class="headerlink" title="解决方案"></a>解决方案</h4><p>将 main.yaml 中 node-version 的配置设置为 13 版本。</p>
<h2 id="参考文档"><a href="#参考文档" class="headerlink" title="参考文档"></a>参考文档</h2><ul>
<li><a href="https://docs.github.com/cn/actions" target="_blank" rel="noopener">Github Action docs</a></li>
<li><a href="https://makefile.so/2021/11/28/use-github-actions-to-deploy-hexo-blog/" target="_blank" rel="noopener">使用 Github Actions 部署 Hexo 博客</a></li>
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<h1 id="2021-年终总结"><a href="#2021-年终总结" class="headerlink" title="2021 年终总结"></a>2021 年终总结</h1><p>还有两天就要结束这一年，迈入新一年了，按照老习惯，趁着放假自己空闲一点，开始回顾自己这一年。想写年终总结时总是思绪万千，但是真的到了输出文字的时候总是写不出什么，可能还是表达能力太差了。</p>
<h2 id="工作"><a href="#工作" class="headerlink" title="工作"></a>工作</h2><p>去年一年，还是在 PingCAP 工作，有的变化只是我从社区部门转岗到商业部门做售前。这个决定经过了很久的思想斗争，但不能算是一个考虑周全的决定。做出决定的那一瞬间，其实也还是有很多凭感觉的地方在，考虑了很多也只是凭借感觉做了选择。之前在做 DBA 的时候有考虑过自己的职业规划，要不就是一直做技术，到可以做成技术专家的程度；另一个选择就是在技术有一定积累之后做售前或者架构师，将技术价值更大化。说实话，按照我心里的预期，我目前的工作经验以及积累还不足以让我觉得我可以做一个售前，但是当有机会时，又不想那么轻易的放弃，毕竟没有那么多等一切都准备好了才有的机会。</p>
<p>从 5 月份开始慢慢接触售前的工作，幸好之前已经对于 TiDB 有了解，所以在技术方面的压力没那么大，可以专心面对跟客户交流、跟人打交道方面的内容。售前的工作给了我更多与人接触的机会，之前我并不是那么喜欢跟人打交道，但是现在不得不去跟人打交道，目前已经习惯了。想想自己刚毕业的时候，连接到别人打的电话都会抵触，不愿意接，到现在主动跟人打电话也可以。感觉变化还是挺大的。</p>
<h2 id="读书"><a href="#读书" class="headerlink" title="读书"></a>读书</h2><p>从今年开始改变了一下统计我一年读书的方式，之前因为年终总结是按照农历年为跨度写的，所以之前读书也是按照一样的时间维度去统计，但是今年感觉这种方式统计可能会有不严谨的地方，所以就按照公历年份去看看自己读了多少书，这样也方便统计。</p>
<p>去年也是一样买了很多书，但是读完的不多。看了一下去年的统计，总共读完了 36 本书，大部分书还都是在微信读书上读完的，实体书没有读多少。读的技术方面的书越来越少了，啃不动了。也没有专门读某一领域方面的书。</p>
<p>给自己记录一本之后有机会还可以再读一遍的书 《鳗鱼的旅行》。</p>
<h2 id="生活"><a href="#生活" class="headerlink" title="生活"></a>生活</h2><p>21 年有一个字很火，那就是 ”卷“。但是我不是一个爱卷的人，所以我选择反卷。21 年选择了更多的时间去生活，或者只是说选择了更少的时间去工作。21 年完成了几件事，首先是去把摩托车驾照考了，也买了自己人生中的第一辆摩托车，在提车回来的第一天就骑着车开了 200 公里（主要的原因是因为杭州禁摩，只能选择绕路将车开回来）。考驾照时是骑的三轮摩托车，从来没有骑过二轮的。胆子很大的，提车那天自己一个人就去了，提车之前在网上看了很久的骑车教程。结果还好，找了一段路练习了一下换挡，然后就 200 公里一路骑回来了。还曾一度骑到了 90+ 码，现在想来还是有点后怕，第一天就这么猛，真的不要命。而且忘记了新车应该要磨合一下。</p>
<p>21 年还完成了连续骑自行车 100 公里的目标，花了一天时间从杭州出发，绕青山湖一圈再骑回杭州，刚好一圈。百公里消耗炒面一碗。也是因为骑自行车在 21 年摔了一跤，把右手手腕摔坏了，本来以为没有伤到骨头没有什么大事，没想到很长时间都不能正常运动，现在做俯卧撑手腕都感觉有点不一样（给自己减肥失败找个理由）。</p>
<p>21 年想学滑雪，没有完成。</p>
<h2 id="最后"><a href="#最后" class="headerlink" title="最后"></a>最后</h2><p>最近学到一个新的词叫深度年（Year of Deepening）。主要意思是这一年让自己往已经了解的领域深挖，而不是不断扩展新的领域或者新的爱好，让自己走的更深，而不是更广。觉得 22 年可以往这个方向靠一靠。</p>
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<a href="/2021/05/09/058-simple-database-4/" class="post-title-link" itemprop="url">Let's Build a Simple Database - Our First Tests(and Bugs)</a>
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<p>原文地址：<a href="https://cstack.github.io/db_tutorial/parts/part4.html" target="_blank" rel="noopener">https://cstack.github.io/db_tutorial/parts/part4.html</a><br>原文作者： <a href="https://github.com/cstack" target="_blank" rel="noopener">cstack</a><br>译者：<a href="https://github.com/Win-Man" target="_blank" rel="noopener">Win-Man</a></p>
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<p>目前为止，我们的数据库具备了插入记录和输出所有记录行的能力。让我们花点时间测试一下目前数据库的能力。</p>
<p>我准备使用 <a href="http://rspec.info/" target="_blank" rel="noopener">rspec</a> 写测试，因为我对这个比较熟悉，并且语法比较易读。</p>
<p>我会定义一个简短的助手去发送一系列命令给我们的数据库程序，然后对返回的输出结果做断言。</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line">describe 'database' do</span><br><span class="line"> def run_script(commands)</span><br><span class="line"> raw_output = nil</span><br><span class="line"> IO.popen("./db", "r+") do |pipe|</span><br><span class="line"> commands.each do |command|</span><br><span class="line"> pipe.puts command</span><br><span class="line"> end</span><br><span class="line"></span><br><span class="line"> pipe.close_write</span><br><span class="line"></span><br><span class="line"> # Read entire output</span><br><span class="line"> raw_output = pipe.gets(nil)</span><br><span class="line"> end</span><br><span class="line"> raw_output.split("\n")</span><br><span class="line"> end</span><br><span class="line"></span><br><span class="line"> it 'inserts and retrieves a row' do</span><br><span class="line"> result = run_script([</span><br><span class="line"> "insert 1 user1 [email protected]",</span><br><span class="line"> "select",</span><br><span class="line"> ".exit",</span><br><span class="line"> ])</span><br><span class="line"> expect(result).to match_array([</span><br><span class="line"> "db > Executed.",</span><br><span class="line"> "db > (1, user1, [email protected])",</span><br><span class="line"> "Executed.",</span><br><span class="line"> "db > ",</span><br><span class="line"> ])</span><br><span class="line"> end</span><br><span class="line">end</span><br></pre></td></tr></table></figure>
<p>这个简单的测试确保了我们得到了和我们输入一样的输出结果，并且这个测试确实通过了：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">bundle exec rspec</span><br><span class="line">.</span><br><span class="line"></span><br><span class="line">Finished in 0.00871 seconds (files took 0.09506 seconds to load)</span><br><span class="line">1 example, 0 failures</span><br></pre></td></tr></table></figure>
<p>然后就可以测试往数据库中插入大量的记录了：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">it 'prints error message when table is full' do</span><br><span class="line"> script = (1..1401).map do |i|</span><br><span class="line"> "insert #{i} user#{i} person#{i}@example.com"</span><br><span class="line"> end</span><br><span class="line"> script << ".exit"</span><br><span class="line"> result = run_script(script)</span><br><span class="line"> expect(result[-2]).to eq('db > Error: Table full.')</span><br><span class="line">end</span><br></pre></td></tr></table></figure>
<p>再重新运行测试。</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">bundle exec rspec</span><br><span class="line">..</span><br><span class="line"></span><br><span class="line">Finished in 0.01553 seconds (files took 0.08156 seconds to load)</span><br><span class="line">2 examples, 0 failures</span><br></pre></td></tr></table></figure>
<p>测试通过了，我们的数据库可以存储 1400 行数据目前，因为我们设置了最大的数据页大小是 100，并且每个数据页上可以存储 14 条记录。</p>
<p>重新翻看我们写的代码，我意识到我们可能没有正确的处理如何存储 text 字段。可以很容易的验证这个 case:</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">it 'allows inserting strings that are the maximum length' do</span><br><span class="line"> long_username = "a"*32</span><br><span class="line"> long_email = "a"*255</span><br><span class="line"> script = [</span><br><span class="line"> "insert 1 #{long_username} #{long_email}",</span><br><span class="line"> "select",</span><br><span class="line"> ".exit",</span><br><span class="line"> ]</span><br><span class="line"> result = run_script(script)</span><br><span class="line"> expect(result).to match_array([</span><br><span class="line"> "db > Executed.",</span><br><span class="line"> "db > (1, #{long_username}, #{long_email})",</span><br><span class="line"> "Executed.",</span><br><span class="line"> "db > ",</span><br><span class="line"> ])</span><br><span class="line">end</span><br></pre></td></tr></table></figure>
<p>然后测试就跑不通了</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">Failures:</span><br><span class="line"></span><br><span class="line"> 1) database allows inserting strings that are the maximum length</span><br><span class="line"> Failure/Error: raw_output.split("\n")</span><br><span class="line"></span><br><span class="line"> ArgumentError:</span><br><span class="line"> invalid byte sequence in UTF-8</span><br><span class="line"> # ./spec/main_spec.rb:14:in `split'</span><br><span class="line"> # ./spec/main_spec.rb:14:in `run_script'</span><br><span class="line"> # ./spec/main_spec.rb:48:in `block (2 levels) in <top (required)>'</span><br></pre></td></tr></table></figure>
<p>如果我们手动测试这个例子，我们可以在输出的记录中看到一些奇怪的字符(我对字符串进行了缩写)：</p>
<figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">db > insert 1 aaaaa... aaaaa...</span><br><span class="line">Executed.</span><br><span class="line">db > select</span><br><span class="line">(1, aaaaa...aaa\�, aaaaa...aaa\�)</span><br><span class="line">Executed.</span><br><span class="line">db ></span><br></pre></td></tr></table></figure>
<p>这是怎么回事？我们再看一下我们对于 Row 的定义，我们给 username 字段分配了 32 字节的空间，email 字段分配了 255 字节的空间。但是 C 语言中 string 类型的字段应该是以 null 字符结尾的，我们并没有给这个结束符分配空间。所以这个问题的结局方案就是多分配一个字节的空间：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"> <span class="keyword">const</span> <span class="keyword">uint32_t</span> COLUMN_EMAIL_SIZE = <span class="number">255</span>;</span><br><span class="line"> <span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line"> <span class="keyword">uint32_t</span> id;</span><br><span class="line">- <span class="keyword">char</span> username[COLUMN_USERNAME_SIZE];</span><br><span class="line">- <span class="keyword">char</span> email[COLUMN_EMAIL_SIZE];</span><br><span class="line">+ <span class="keyword">char</span> username[COLUMN_USERNAME_SIZE + <span class="number">1</span>];</span><br><span class="line">+ <span class="keyword">char</span> email[COLUMN_EMAIL_SIZE + <span class="number">1</span>];</span><br><span class="line"> } Row;</span><br></pre></td></tr></table></figure>
<p>再次运行测试，可以看到测试通过了</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"> bundle exec rspec</span><br><span class="line">...</span><br><span class="line"></span><br><span class="line">Finished in 0.0188 seconds (files took 0.08516 seconds to load)</span><br><span class="line">3 examples, 0 failures</span><br></pre></td></tr></table></figure>
<p>我们不应该允许插入的 username 和 email 字段的值超过我们定义的 column size ，可以增加一个测试：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">it 'prints error message if strings are too long' do</span><br><span class="line"> long_username = "a"*33</span><br><span class="line"> long_email = "a"*256</span><br><span class="line"> script = [</span><br><span class="line"> "insert 1 #{long_username} #{long_email}",</span><br><span class="line"> "select",</span><br><span class="line"> ".exit",</span><br><span class="line"> ]</span><br><span class="line"> result = run_script(script)</span><br><span class="line"> expect(result).to match_array([</span><br><span class="line"> "db > String is too long.",</span><br><span class="line"> "db > Executed.",</span><br><span class="line"> "db > ",</span><br><span class="line"> ])</span><br><span class="line">end</span><br></pre></td></tr></table></figure>
<p>为了实现这个限制，我们需要更新一下我们的 parser 解析器。目前使用的是 scanf()：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">if</span> (<span class="built_in">strncmp</span>(input_buffer->buffer, <span class="string">"insert"</span>, <span class="number">6</span>) == <span class="number">0</span>) {</span><br><span class="line"> statement->type = STATEMENT_INSERT;</span><br><span class="line"> <span class="keyword">int</span> args_assigned = <span class="built_in">sscanf</span>(</span><br><span class="line"> input_buffer->buffer, <span class="string">"insert %d %s %s"</span>, &(statement->row_to_insert.id),</span><br><span class="line"> statement->row_to_insert.username, statement->row_to_insert.email);</span><br><span class="line"> <span class="keyword">if</span> (args_assigned < <span class="number">3</span>) {</span><br><span class="line"> <span class="keyword">return</span> PREPARE_SYNTAX_ERROR;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> PREPARE_SUCCESS;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>但是 scanf() 有一些缺点。如果读取的字符串大小超过了分配的空间，会导致缓存溢出并且数据会被写入到未知的空间。我们需要在拷贝数据到 Row 结构体之前先检查一下字符串的长度。为了实现这个，我们需要将输入通过空格切割一下。</p>
<p>我准备试用 strtok() 来实现这个。这个比较容易理解：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br></pre></td><td class="code"><pre><span class="line">+<span class="function">PrepareResult <span class="title">prepare_insert</span><span class="params">(InputBuffer* input_buffer, Statement* statement)</span> </span>{</span><br><span class="line">+ statement->type = STATEMENT_INSERT;</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">char</span>* keyword = strtok(input_buffer->buffer, <span class="string">" "</span>);</span><br><span class="line">+ <span class="keyword">char</span>* id_string = strtok(<span class="literal">NULL</span>, <span class="string">" "</span>);</span><br><span class="line">+ <span class="keyword">char</span>* username = strtok(<span class="literal">NULL</span>, <span class="string">" "</span>);</span><br><span class="line">+ <span class="keyword">char</span>* email = strtok(<span class="literal">NULL</span>, <span class="string">" "</span>);</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">if</span> (id_string == <span class="literal">NULL</span> || username == <span class="literal">NULL</span> || email == <span class="literal">NULL</span>) {</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_SYNTAX_ERROR;</span><br><span class="line">+ }</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">int</span> id = atoi(id_string);</span><br><span class="line">+ <span class="keyword">if</span> (<span class="built_in">strlen</span>(username) > COLUMN_USERNAME_SIZE) {</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_STRING_TOO_LONG;</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">if</span> (<span class="built_in">strlen</span>(email) > COLUMN_EMAIL_SIZE) {</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_STRING_TOO_LONG;</span><br><span class="line">+ }</span><br><span class="line">+</span><br><span class="line">+ statement->row_to_insert.id = id;</span><br><span class="line">+ <span class="built_in">strcpy</span>(statement->row_to_insert.username, username);</span><br><span class="line">+ <span class="built_in">strcpy</span>(statement->row_to_insert.email, email);</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_SUCCESS;</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line"> <span class="function">PrepareResult <span class="title">prepare_statement</span><span class="params">(InputBuffer* input_buffer,</span></span></span><br><span class="line"><span class="function"><span class="params"> Statement* statement)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (<span class="built_in">strncmp</span>(input_buffer->buffer, <span class="string">"insert"</span>, <span class="number">6</span>) == <span class="number">0</span>) {</span><br><span class="line">+ <span class="keyword">return</span> prepare_insert(input_buffer, statement);</span><br><span class="line">- statement->type = STATEMENT_INSERT;</span><br><span class="line">- <span class="keyword">int</span> args_assigned = <span class="built_in">sscanf</span>(</span><br><span class="line">- input_buffer->buffer, <span class="string">"insert %d %s %s"</span>, &(statement->row_to_insert.id),</span><br><span class="line">- statement->row_to_insert.username, statement->row_to_insert.email);</span><br><span class="line">- <span class="keyword">if</span> (args_assigned < <span class="number">3</span>) {</span><br><span class="line">- <span class="keyword">return</span> PREPARE_SYNTAX_ERROR;</span><br><span class="line">- }</span><br><span class="line">- <span class="keyword">return</span> PREPARE_SUCCESS;</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<p>在输入缓冲区上连续调用strtok，每当缓冲区到达分隔符(在本例中是空格)时，就插入一个空字符，从而将它分解为子字符串。它返回一个指向子字符串开头的指针。</p>
<p>可以调用 strlen() 函数确认每个 text 字段值是不是超过了长度限制。</p>
<p>我们可以像处理别的错误一样处理这个错误：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"> <span class="keyword">enum</span> PrepareResult_t {</span><br><span class="line"> PREPARE_SUCCESS,</span><br><span class="line">+ PREPARE_STRING_TOO_LONG,</span><br><span class="line"> PREPARE_SYNTAX_ERROR,</span><br><span class="line"> PREPARE_UNRECOGNIZED_STATEMENT</span><br><span class="line"> };</span><br></pre></td></tr></table></figure>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"> <span class="keyword">switch</span> (prepare_statement(input_buffer, &statement)) {</span><br><span class="line"> <span class="keyword">case</span> (PREPARE_SUCCESS):</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_STRING_TOO_LONG):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"String is too long.\n"</span>);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line"> <span class="keyword">case</span> (PREPARE_SYNTAX_ERROR):</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"Syntax error. Could not parse statement.\n"</span>);</span><br><span class="line"> <span class="keyword">continue</span>;</span><br></pre></td></tr></table></figure>
<p>再次运行测试，测试通过</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">bundle exec rspec</span><br><span class="line">....</span><br><span class="line"></span><br><span class="line">Finished in 0.02284 seconds (files took 0.116 seconds to load)</span><br><span class="line">4 examples, 0 failures</span><br></pre></td></tr></table></figure>
<p>既然已经增加了一种错误情况，我们不妨再处理一个错误情况:</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">it 'prints an error message if id is negative' do</span><br><span class="line"> script = [</span><br><span class="line"> "insert -1 cstack [email protected]",</span><br><span class="line"> "select",</span><br><span class="line"> ".exit",</span><br><span class="line"> ]</span><br><span class="line"> result = run_script(script)</span><br><span class="line"> expect(result).to match_array([</span><br><span class="line"> "db > ID must be positive.",</span><br><span class="line"> "db > Executed.",</span><br><span class="line"> "db > ",</span><br><span class="line"> ])</span><br><span class="line">end</span><br></pre></td></tr></table></figure>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line"> <span class="keyword">enum</span> PrepareResult_t {</span><br><span class="line"> PREPARE_SUCCESS,</span><br><span class="line">+ PREPARE_NEGATIVE_ID,</span><br><span class="line"> PREPARE_STRING_TOO_LONG,</span><br><span class="line"> PREPARE_SYNTAX_ERROR,</span><br><span class="line"> PREPARE_UNRECOGNIZED_STATEMENT</span><br><span class="line">@@ <span class="number">-148</span>,<span class="number">9</span> +<span class="number">147</span>,<span class="number">6</span> @@ <span class="function">PrepareResult <span class="title">prepare_insert</span><span class="params">(InputBuffer* input_buffer, Statement* statement)</span> </span>{</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">int</span> id = atoi(id_string);</span><br><span class="line">+ <span class="keyword">if</span> (id < <span class="number">0</span>) {</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_NEGATIVE_ID;</span><br><span class="line">+ }</span><br><span class="line"> <span class="keyword">if</span> (<span class="built_in">strlen</span>(username) > COLUMN_USERNAME_SIZE) {</span><br><span class="line"> <span class="keyword">return</span> PREPARE_STRING_TOO_LONG;</span><br><span class="line"> }</span><br><span class="line">@@ <span class="number">-230</span>,<span class="number">9</span> +<span class="number">226</span>,<span class="number">6</span> @@ <span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">(<span class="keyword">int</span> argc, <span class="keyword">char</span>* argv[])</span> </span>{</span><br><span class="line"> <span class="keyword">switch</span> (prepare_statement(input_buffer, &statement)) {</span><br><span class="line"> <span class="keyword">case</span> (PREPARE_SUCCESS):</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_NEGATIVE_ID):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"ID must be positive.\n"</span>);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line"> <span class="keyword">case</span> (PREPARE_STRING_TOO_LONG):</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"String is too long.\n"</span>);</span><br><span class="line"> <span class="keyword">continue</span>;</span><br></pre></td></tr></table></figure>
<p>目前这些测试已经足够了，下一个章节会是一个重要的特性：持久化。我们需要将数据存储到文件中，并且中文件中读取出来。</p>
<p>那会很棒的。</p>
<p>在这给出这个部分中与之前代码不同的部分：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br></pre></td><td class="code"><pre><span class="line">@@ <span class="number">-22</span>,<span class="number">6</span> +<span class="number">22</span>,<span class="number">8</span> @@</span><br><span class="line"></span><br><span class="line"> <span class="keyword">enum</span> PrepareResult_t {</span><br><span class="line"> PREPARE_SUCCESS,</span><br><span class="line">+ PREPARE_NEGATIVE_ID,</span><br><span class="line">+ PREPARE_STRING_TOO_LONG,</span><br><span class="line"> PREPARE_SYNTAX_ERROR,</span><br><span class="line"> PREPARE_UNRECOGNIZED_STATEMENT</span><br><span class="line"> };</span><br><span class="line">@@ <span class="number">-34</span>,<span class="number">8</span> +<span class="number">36</span>,<span class="number">8</span> @@</span><br><span class="line"> <span class="meta">#<span class="meta-keyword">define</span> COLUMN_EMAIL_SIZE 255</span></span><br><span class="line"> <span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line"> <span class="keyword">uint32_t</span> id;</span><br><span class="line">- <span class="keyword">char</span> username[COLUMN_USERNAME_SIZE];</span><br><span class="line">- <span class="keyword">char</span> email[COLUMN_EMAIL_SIZE];</span><br><span class="line">+ <span class="keyword">char</span> username[COLUMN_USERNAME_SIZE + <span class="number">1</span>];</span><br><span class="line">+ <span class="keyword">char</span> email[COLUMN_EMAIL_SIZE + <span class="number">1</span>];</span><br><span class="line"> } Row;</span><br><span class="line"></span><br><span class="line">@@ <span class="number">-150</span>,<span class="number">18</span> +<span class="number">152</span>,<span class="number">40</span> @@ <span class="function">MetaCommandResult <span class="title">do_meta_command</span><span class="params">(InputBuffer* input_buffer, Table *table)</span> </span>{</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line">-<span class="function">PrepareResult <span class="title">prepare_statement</span><span class="params">(InputBuffer* input_buffer,</span></span></span><br><span class="line"><span class="function"><span class="params">- Statement* statement)</span> </span>{</span><br><span class="line">- <span class="keyword">if</span> (<span class="built_in">strncmp</span>(input_buffer->buffer, <span class="string">"insert"</span>, <span class="number">6</span>) == <span class="number">0</span>) {</span><br><span class="line">+<span class="function">PrepareResult <span class="title">prepare_insert</span><span class="params">(InputBuffer* input_buffer, Statement* statement)</span> </span>{</span><br><span class="line"> statement->type = STATEMENT_INSERT;</span><br><span class="line">- <span class="keyword">int</span> args_assigned = <span class="built_in">sscanf</span>(</span><br><span class="line">- input_buffer->buffer, <span class="string">"insert %d %s %s"</span>, &(statement->row_to_insert.id),</span><br><span class="line">- statement->row_to_insert.username, statement->row_to_insert.email</span><br><span class="line">- );</span><br><span class="line">- <span class="keyword">if</span> (args_assigned < <span class="number">3</span>) {</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">char</span>* keyword = strtok(input_buffer->buffer, <span class="string">" "</span>);</span><br><span class="line">+ <span class="keyword">char</span>* id_string = strtok(<span class="literal">NULL</span>, <span class="string">" "</span>);</span><br><span class="line">+ <span class="keyword">char</span>* username = strtok(<span class="literal">NULL</span>, <span class="string">" "</span>);</span><br><span class="line">+ <span class="keyword">char</span>* email = strtok(<span class="literal">NULL</span>, <span class="string">" "</span>);</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">if</span> (id_string == <span class="literal">NULL</span> || username == <span class="literal">NULL</span> || email == <span class="literal">NULL</span>) {</span><br><span class="line"> <span class="keyword">return</span> PREPARE_SYNTAX_ERROR;</span><br><span class="line"> }</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">int</span> id = atoi(id_string);</span><br><span class="line">+ <span class="keyword">if</span> (id < <span class="number">0</span>) {</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_NEGATIVE_ID;</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">if</span> (<span class="built_in">strlen</span>(username) > COLUMN_USERNAME_SIZE) {</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_STRING_TOO_LONG;</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">if</span> (<span class="built_in">strlen</span>(email) > COLUMN_EMAIL_SIZE) {</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_STRING_TOO_LONG;</span><br><span class="line">+ }</span><br><span class="line">+</span><br><span class="line">+ statement->row_to_insert.id = id;</span><br><span class="line">+ <span class="built_in">strcpy</span>(statement->row_to_insert.username, username);</span><br><span class="line">+ <span class="built_in">strcpy</span>(statement->row_to_insert.email, email);</span><br><span class="line">+</span><br><span class="line"> <span class="keyword">return</span> PREPARE_SUCCESS;</span><br><span class="line">+</span><br><span class="line">+}</span><br><span class="line">+<span class="function">PrepareResult <span class="title">prepare_statement</span><span class="params">(InputBuffer* input_buffer,</span></span></span><br><span class="line"><span class="function"><span class="params">+ Statement* statement)</span> </span>{</span><br><span class="line">+ <span class="keyword">if</span> (<span class="built_in">strncmp</span>(input_buffer->buffer, <span class="string">"insert"</span>, <span class="number">6</span>) == <span class="number">0</span>) {</span><br><span class="line">+ <span class="keyword">return</span> prepare_insert(input_buffer, statement);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (<span class="built_in">strcmp</span>(input_buffer->buffer, <span class="string">"select"</span>) == <span class="number">0</span>) {</span><br><span class="line"> statement->type = STATEMENT_SELECT;</span><br><span class="line">@@ <span class="number">-223</span>,<span class="number">6</span> +<span class="number">247</span>,<span class="number">12</span> @@ <span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">(<span class="keyword">int</span> argc, <span class="keyword">char</span>* argv[])</span> </span>{</span><br><span class="line"> <span class="keyword">switch</span> (prepare_statement(input_buffer, &statement)) {</span><br><span class="line"> <span class="keyword">case</span> (PREPARE_SUCCESS):</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_NEGATIVE_ID):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"ID must be positive.\n"</span>);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_STRING_TOO_LONG):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"String is too long.\n"</span>);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line"> <span class="keyword">case</span> (PREPARE_SYNTAX_ERROR):</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"Syntax error. Could not parse statement.\n"</span>);</span><br><span class="line"> <span class="keyword">continue</span>;</span><br></pre></td></tr></table></figure>
<p>以及我们增加的测试:</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br></pre></td><td class="code"><pre><span class="line">+describe 'database' do</span><br><span class="line">+ def run_script(commands)</span><br><span class="line">+ raw_output = nil</span><br><span class="line">+ IO.popen("./db", "r+") do |pipe|</span><br><span class="line">+ commands.each do |command|</span><br><span class="line">+ pipe.puts command</span><br><span class="line">+ end</span><br><span class="line">+</span><br><span class="line">+ pipe.close_write</span><br><span class="line">+</span><br><span class="line">+ # Read entire output</span><br><span class="line">+ raw_output = pipe.gets(nil)</span><br><span class="line">+ end</span><br><span class="line">+ raw_output.split("\n")</span><br><span class="line">+ end</span><br><span class="line">+</span><br><span class="line">+ it 'inserts and retrieves a row' do</span><br><span class="line">+ result = run_script([</span><br><span class="line">+ "insert 1 user1 [email protected]",</span><br><span class="line">+ "select",</span><br><span class="line">+ ".exit",</span><br><span class="line">+ ])</span><br><span class="line">+ expect(result).to match_array([</span><br><span class="line">+ "db > Executed.",</span><br><span class="line">+ "db > (1, user1, [email protected])",</span><br><span class="line">+ "Executed.",</span><br><span class="line">+ "db > ",</span><br><span class="line">+ ])</span><br><span class="line">+ end</span><br><span class="line">+</span><br><span class="line">+ it 'prints error message when table is full' do</span><br><span class="line">+ script = (1..1401).map do |i|</span><br><span class="line">+ "insert #{i} user#{i} person#{i}@example.com"</span><br><span class="line">+ end</span><br><span class="line">+ script << ".exit"</span><br><span class="line">+ result = run_script(script)</span><br><span class="line">+ expect(result[-2]).to eq('db > Error: Table full.')</span><br><span class="line">+ end</span><br><span class="line">+</span><br><span class="line">+ it 'allows inserting strings that are the maximum length' do</span><br><span class="line">+ long_username = "a"*32</span><br><span class="line">+ long_email = "a"*255</span><br><span class="line">+ script = [</span><br><span class="line">+ "insert 1 #{long_username} #{long_email}",</span><br><span class="line">+ "select",</span><br><span class="line">+ ".exit",</span><br><span class="line">+ ]</span><br><span class="line">+ result = run_script(script)</span><br><span class="line">+ expect(result).to match_array([</span><br><span class="line">+ "db > Executed.",</span><br><span class="line">+ "db > (1, #{long_username}, #{long_email})",</span><br><span class="line">+ "Executed.",</span><br><span class="line">+ "db > ",</span><br><span class="line">+ ])</span><br><span class="line">+ end</span><br><span class="line">+</span><br><span class="line">+ it 'prints error message if strings are too long' do</span><br><span class="line">+ long_username = "a"*33</span><br><span class="line">+ long_email = "a"*256</span><br><span class="line">+ script = [</span><br><span class="line">+ "insert 1 #{long_username} #{long_email}",</span><br><span class="line">+ "select",</span><br><span class="line">+ ".exit",</span><br><span class="line">+ ]</span><br><span class="line">+ result = run_script(script)</span><br><span class="line">+ expect(result).to match_array([</span><br><span class="line">+ "db > String is too long.",</span><br><span class="line">+ "db > Executed.",</span><br><span class="line">+ "db > ",</span><br><span class="line">+ ])</span><br><span class="line">+ end</span><br><span class="line">+</span><br><span class="line">+ it 'prints an error message if id is negative' do</span><br><span class="line">+ script = [</span><br><span class="line">+ "insert -1 cstack [email protected]",</span><br><span class="line">+ "select",</span><br><span class="line">+ ".exit",</span><br><span class="line">+ ]</span><br><span class="line">+ result = run_script(script)</span><br><span class="line">+ expect(result).to match_array([</span><br><span class="line">+ "db > ID must be positive.",</span><br><span class="line">+ "db > Executed.",</span><br><span class="line">+ "db > ",</span><br><span class="line">+ ])</span><br><span class="line">+ end</span><br><span class="line">+end</span><br></pre></td></tr></table></figure>
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<a href="/2021/05/06/057-simple-database-3/" class="post-title-link" itemprop="url">Let's Build a Simple Database - An In-Memory,Append-Only,Sinle-Table Database</a>
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<p>原文地址：<a href="https://cstack.github.io/db_tutorial/parts/part3.html" target="_blank" rel="noopener">https://cstack.github.io/db_tutorial/parts/part3.html</a><br>原文作者： <a href="https://github.com/cstack" target="_blank" rel="noopener">cstack</a><br>译者：<a href="https://github.com/Win-Man" target="_blank" rel="noopener">Win-Man</a></p>
</blockquote>
<p>我们通过在我们数据库上设置很多限制，从一个小的数据库开始。这一节，我们会做这些内容：</p>
<ul>
<li>支持两种操作：插入一行数据和查询出所有数据行</li>
<li>将数据存储在内存中（不持久化到硬盘上）</li>
<li>支持单个、表结构固定的表</li>
</ul>
<p>我们表结构固定的表示用于存储用户的，结构是：</p>
<table>
<thead>
<tr>
<th>column</th>
<th>type</th>
</tr>
</thead>
<tbody>
<tr>
<td>id</td>
<td>integer</td>
</tr>
<tr>
<td>username</td>
<td>varchar(32)</td>
</tr>
<tr>
<td>email</td>
<td>varchar(255)</td>
</tr>
</tbody>
</table>
<p>这是一个简单的表结构，但是可以让我们去支持多种数据格式和多种数据大小。</p>
<p>insert 语句会类似于这个形式</p>
<figure class="highlight sql"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">insert</span> <span class="number">1</span> cstack [email protected]</span><br></pre></td></tr></table></figure>
<p>这意味着我们需要更新我们的 <code>prepare_statement</code> 函数去解析参数</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"> <span class="keyword">if</span> (<span class="built_in">strncmp</span>(input_buffer->buffer, <span class="string">"insert"</span>, <span class="number">6</span>) == <span class="number">0</span>) {</span><br><span class="line"> statement->type = STATEMENT_INSERT;</span><br><span class="line">+ <span class="keyword">int</span> args_assigned = <span class="built_in">sscanf</span>(</span><br><span class="line">+ input_buffer->buffer, <span class="string">"insert %d %s %s"</span>, &(statement->row_to_insert.id),</span><br><span class="line">+ statement->row_to_insert.username, statement->row_to_insert.email);</span><br><span class="line">+ <span class="keyword">if</span> (args_assigned < <span class="number">3</span>) {</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_SYNTAX_ERROR;</span><br><span class="line">+ }</span><br><span class="line"> <span class="keyword">return</span> PREPARE_SUCCESS;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (<span class="built_in">strcmp</span>(input_buffer->buffer, <span class="string">"select"</span>) == <span class="number">0</span>) {</span><br></pre></td></tr></table></figure>
<p>我们将这些解析出来的参数存储到一个 Row 数据结构中：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">+<span class="meta">#<span class="meta-keyword">define</span> COLUMN_USERNAME_SIZE 32</span></span><br><span class="line">+<span class="meta">#<span class="meta-keyword">define</span> COLUMN_EMAIL_SIZE 255</span></span><br><span class="line">+<span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line">+ <span class="keyword">uint32_t</span> id;</span><br><span class="line">+ <span class="keyword">char</span> username[COLUMN_USERNAME_SIZE];</span><br><span class="line">+ <span class="keyword">char</span> email[COLUMN_EMAIL_SIZE];</span><br><span class="line">+} Row;</span><br><span class="line">+</span><br><span class="line"> <span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line"> StatementType type;</span><br><span class="line">+ Row row_to_insert; <span class="comment">// only used by insert statement</span></span><br><span class="line"> } Statement;</span><br></pre></td></tr></table></figure>
<p>现在我们需要将 Row 结构体中的数据拷贝到能代表 table 数据的结构中。 SQLite 使用了 B-tree 数据结构，可以提升查询、插入、删除的速度。我们开始的会更简单一点。类似于 B-tree, 会将行记录分组到 page 页上，但是是将这些数据页以数据形式存储，而不是以树的形式存储。</p>
<p>我们的计划是：</p>
<ul>
<li>将数据行存储在内存页中</li>
<li>每个数据页可以存储尽可能多的行</li>
<li>记录行被序列化成一种压缩的形式</li>
<li>数据页只有在需要的时候才会分配</li>
<li>保持一个固定大小的数据页指针数组</li>
</ul>
<p>首先，我们需要定义一下一行记录的压缩格式是怎么样的：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">+<span class="meta">#<span class="meta-keyword">define</span> size_of_attribute(Struct, Attribute) sizeof(((Struct*)0)->Attribute)</span></span><br><span class="line">+</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> ID_SIZE = size_of_attribute(Row, id);</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> USERNAME_SIZE = size_of_attribute(Row, username);</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> EMAIL_SIZE = size_of_attribute(Row, email);</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> ID_OFFSET = <span class="number">0</span>;</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> USERNAME_OFFSET = ID_OFFSET + ID_SIZE;</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> EMAIL_OFFSET = USERNAME_OFFSET + USERNAME_SIZE;</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> ROW_SIZE = ID_SIZE + USERNAME_SIZE + EMAIL_SIZE;</span><br></pre></td></tr></table></figure>
<p>这意味着被序列化之后的一行数据会是这样的：</p>
<table>
<thead>
<tr>
<th>column</th>
<th>size(bytes)</th>
<th>offset</th>
</tr>
</thead>
<tbody>
<tr>
<td>id</td>
<td>4</td>
<td>0</td>
</tr>
<tr>
<td>username</td>
<td>32</td>
<td>4</td>
</tr>
<tr>
<td>email</td>
<td>255</td>
<td>36</td>
</tr>
<tr>
<td>total</td>
<td>291</td>
</tr>
</tbody>
</table>
<p>我们也需要将编写转换、反转换的代码.</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">+<span class="function"><span class="keyword">void</span> <span class="title">serialize_row</span><span class="params">(Row* source, <span class="keyword">void</span>* destination)</span> </span>{</span><br><span class="line">+ <span class="built_in">memcpy</span>(destination + ID_OFFSET, &(source->id), ID_SIZE);</span><br><span class="line">+ <span class="built_in">memcpy</span>(destination + USERNAME_OFFSET, &(source->username), USERNAME_SIZE);</span><br><span class="line">+ <span class="built_in">memcpy</span>(destination + EMAIL_OFFSET, &(source->email), EMAIL_SIZE);</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function"><span class="keyword">void</span> <span class="title">deserialize_row</span><span class="params">(<span class="keyword">void</span>* source, Row* destination)</span> </span>{</span><br><span class="line">+ <span class="built_in">memcpy</span>(&(destination->id), source + ID_OFFSET, ID_SIZE);</span><br><span class="line">+ <span class="built_in">memcpy</span>(&(destination->username), source + USERNAME_OFFSET, USERNAME_SIZE);</span><br><span class="line">+ <span class="built_in">memcpy</span>(&(destination->email), source + EMAIL_OFFSET, EMAIL_SIZE);</span><br><span class="line">+}</span><br></pre></td></tr></table></figure>
<p>接着，Table 的数据结构就是一个数据页指针和记录这个表内有多少数据：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> PAGE_SIZE = <span class="number">4096</span>;</span><br><span class="line">+<span class="meta">#<span class="meta-keyword">define</span> TABLE_MAX_PAGES 100</span></span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> ROWS_PER_PAGE = PAGE_SIZE / ROW_SIZE;</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> TABLE_MAX_ROWS = ROWS_PER_PAGE * TABLE_MAX_PAGES;</span><br><span class="line">+</span><br><span class="line">+<span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line">+ <span class="keyword">uint32_t</span> num_rows;</span><br><span class="line">+ <span class="keyword">void</span>* pages[TABLE_MAX_PAGES];</span><br><span class="line">+} Table;</span><br></pre></td></tr></table></figure>
<p>我将我们数据页的大小设置为了 4KB ，因为这也是大多数操作系统使用的数据页大小。意味着我们的使用的数据页大小和操作系统数据页大小是一致的。操作系统会将数据页作为一个整体进行交换，而不是将他们拆散成多个数据页。</p>
<p>我随意设置了一个限制，限制我们只能分配 100 个数据页。当我们转成树结构的时候，我们数据库的最大大小受限于单个文件的大小（尽管我们还是有设置我们在内存中保留多少数据页）</p>
<p>一行数据不能跨数据页存储。因为相邻的数据页可能不会同时存在在内存中，这个限制可以让读写行数据更加容易。</p>
<p>说到这个，看一下我们是如果在内存中定位到需要读取的某一行数据的：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">+<span class="function"><span class="keyword">void</span>* <span class="title">row_slot</span><span class="params">(Table* table, <span class="keyword">uint32_t</span> row_num)</span> </span>{</span><br><span class="line">+ <span class="keyword">uint32_t</span> page_num = row_num / ROWS_PER_PAGE;</span><br><span class="line">+ <span class="keyword">void</span>* page = table->pages[page_num];</span><br><span class="line">+ <span class="keyword">if</span> (page == <span class="literal">NULL</span>) {</span><br><span class="line">+ <span class="comment">// Allocate memory only when we try to access page</span></span><br><span class="line">+ page = table->pages[page_num] = <span class="built_in">malloc</span>(PAGE_SIZE);</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">uint32_t</span> row_offset = row_num % ROWS_PER_PAGE;</span><br><span class="line">+ <span class="keyword">uint32_t</span> byte_offset = row_offset * ROW_SIZE;</span><br><span class="line">+ <span class="keyword">return</span> page + byte_offset;</span><br><span class="line">+}</span><br></pre></td></tr></table></figure>
<p>现在我们可以让 execute_statement 从表结构体中读取或者写入数据了：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br></pre></td><td class="code"><pre><span class="line">-<span class="function"><span class="keyword">void</span> <span class="title">execute_statement</span><span class="params">(Statement* statement)</span> </span>{</span><br><span class="line">+<span class="function">ExecuteResult <span class="title">execute_insert</span><span class="params">(Statement* statement, Table* table)</span> </span>{</span><br><span class="line">+ <span class="keyword">if</span> (table->num_rows >= TABLE_MAX_ROWS) {</span><br><span class="line">+ <span class="keyword">return</span> EXECUTE_TABLE_FULL;</span><br><span class="line">+ }</span><br><span class="line">+</span><br><span class="line">+ Row* row_to_insert = &(statement->row_to_insert);</span><br><span class="line">+</span><br><span class="line">+ serialize_row(row_to_insert, row_slot(table, table->num_rows));</span><br><span class="line">+ table->num_rows += <span class="number">1</span>;</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">return</span> EXECUTE_SUCCESS;</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function">ExecuteResult <span class="title">execute_select</span><span class="params">(Statement* statement, Table* table)</span> </span>{</span><br><span class="line">+ Row row;</span><br><span class="line">+ <span class="keyword">for</span> (<span class="keyword">uint32_t</span> i = <span class="number">0</span>; i < table->num_rows; i++) {</span><br><span class="line">+ deserialize_row(row_slot(table, i), &row);</span><br><span class="line">+ print_row(&row);</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">return</span> EXECUTE_SUCCESS;</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function">ExecuteResult <span class="title">execute_statement</span><span class="params">(Statement* statement, Table* table)</span> </span>{</span><br><span class="line"> <span class="keyword">switch</span> (statement->type) {</span><br><span class="line"> <span class="keyword">case</span> (STATEMENT_INSERT):</span><br><span class="line">- <span class="built_in">printf</span>(<span class="string">"This is where we would do an insert.\n"</span>);</span><br><span class="line">- <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">return</span> execute_insert(statement, table);</span><br><span class="line"> <span class="keyword">case</span> (STATEMENT_SELECT):</span><br><span class="line">- <span class="built_in">printf</span>(<span class="string">"This is where we would do a select.\n"</span>);</span><br><span class="line">- <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">return</span> execute_select(statement, table);</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<p>最后，我们需要初始化一下表，创建释放各自内存的函数以及处理更多错误的情况：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">+ <span class="function">Table* <span class="title">new_table</span><span class="params">()</span> </span>{</span><br><span class="line">+ Table* table = <span class="built_in">malloc</span>(<span class="keyword">sizeof</span>(Table));</span><br><span class="line">+ table->num_rows = <span class="number">0</span>;</span><br><span class="line">+ <span class="keyword">for</span> (<span class="keyword">uint32_t</span> i = <span class="number">0</span>; i < TABLE_MAX_PAGES; i++) {</span><br><span class="line">+ table->pages[i] = <span class="literal">NULL</span>;</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">return</span> table;</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function"><span class="keyword">void</span> <span class="title">free_table</span><span class="params">(Table* table)</span> </span>{</span><br><span class="line">+ <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; table->pages[i]; i++) {</span><br><span class="line">+ <span class="built_in">free</span>(table->pages[i]);</span><br><span class="line">+ }</span><br><span class="line">+ <span class="built_in">free</span>(table);</span><br><span class="line">+}</span><br></pre></td></tr></table></figure>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">(<span class="keyword">int</span> argc, <span class="keyword">char</span>* argv[])</span> </span>{</span><br><span class="line">+ Table* table = new_table();</span><br><span class="line"> InputBuffer* input_buffer = new_input_buffer();</span><br><span class="line"> <span class="keyword">while</span> (<span class="literal">true</span>) {</span><br><span class="line"> print_prompt();</span><br><span class="line">@@ <span class="number">-105</span>,<span class="number">13</span> +<span class="number">203</span>,<span class="number">22</span> @@ <span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">(<span class="keyword">int</span> argc, <span class="keyword">char</span>* argv[])</span> </span>{</span><br><span class="line"> <span class="keyword">switch</span> (prepare_statement(input_buffer, &statement)) {</span><br><span class="line"> <span class="keyword">case</span> (PREPARE_SUCCESS):</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_SYNTAX_ERROR):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Syntax error. Could not parse statement.\n"</span>);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line"> <span class="keyword">case</span> (PREPARE_UNRECOGNIZED_STATEMENT):</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"Unrecognized keyword at start of '%s'.\n"</span>,</span><br><span class="line"> input_buffer->buffer);</span><br><span class="line"> <span class="keyword">continue</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line">- execute_statement(&statement);</span><br><span class="line">- <span class="built_in">printf</span>(<span class="string">"Executed.\n"</span>);</span><br><span class="line">+ <span class="keyword">switch</span> (execute_statement(&statement, table)) {</span><br><span class="line">+ <span class="keyword">case</span> (EXECUTE_SUCCESS):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Executed.\n"</span>);</span><br><span class="line">+ <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">case</span> (EXECUTE_TABLE_FULL):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Error: Table full.\n"</span>);</span><br><span class="line">+ <span class="keyword">break</span>;</span><br><span class="line">+ }</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<p>经过这些修改，我们就可以真正的在我们的数据库中存储数据了</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">~ ./db</span><br><span class="line">db > insert 1 cstack [email protected]</span><br><span class="line">Executed.</span><br><span class="line">db > insert 2 bob [email protected]</span><br><span class="line">Executed.</span><br><span class="line">db > select</span><br><span class="line">(1, cstack, [email protected])</span><br><span class="line">(2, bob, [email protected])</span><br><span class="line">Executed.</span><br><span class="line">db > insert foo bar 1</span><br><span class="line">Syntax error. Could not parse statement.</span><br><span class="line">db > .exit</span><br></pre></td></tr></table></figure>
<p>这时候是写一些测试的好时候了，因为以下几个原因：</p>
<ul>
<li>我们计划修改数据结构去存储我们的表，有测试的话可以方便捕捉到回归错误</li>
<li>有一些边缘 case 我们没有手动测试（比如填满一张表）</li>
</ul>
<p>我们会在下一个部分做这些内容。现在先看下这个部分完整修改的内容：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br><span class="line">119</span><br><span class="line">120</span><br><span class="line">121</span><br><span class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br><span class="line">128</span><br><span class="line">129</span><br><span class="line">130</span><br><span class="line">131</span><br><span class="line">132</span><br><span class="line">133</span><br><span class="line">134</span><br><span class="line">135</span><br><span class="line">136</span><br><span class="line">137</span><br><span class="line">138</span><br><span class="line">139</span><br><span class="line">140</span><br><span class="line">141</span><br><span class="line">142</span><br><span class="line">143</span><br><span class="line">144</span><br><span class="line">145</span><br><span class="line">146</span><br><span class="line">147</span><br><span class="line">148</span><br><span class="line">149</span><br><span class="line">150</span><br><span class="line">151</span><br><span class="line">152</span><br><span class="line">153</span><br><span class="line">154</span><br><span class="line">155</span><br><span class="line">156</span><br><span class="line">157</span><br><span class="line">158</span><br><span class="line">159</span><br><span class="line">160</span><br><span class="line">161</span><br><span class="line">162</span><br><span class="line">163</span><br><span class="line">164</span><br><span class="line">165</span><br><span class="line">166</span><br><span class="line">167</span><br><span class="line">168</span><br><span class="line">169</span><br><span class="line">170</span><br><span class="line">171</span><br><span class="line">172</span><br><span class="line">173</span><br><span class="line">174</span><br><span class="line">175</span><br><span class="line">176</span><br><span class="line">177</span><br><span class="line">178</span><br><span class="line">179</span><br><span class="line">180</span><br><span class="line">181</span><br><span class="line">182</span><br><span class="line">183</span><br><span class="line">184</span><br><span class="line">185</span><br><span class="line">186</span><br><span class="line">187</span><br><span class="line">188</span><br><span class="line">189</span><br><span class="line">190</span><br><span class="line">191</span><br><span class="line">192</span><br><span class="line">193</span><br><span class="line">194</span><br><span class="line">195</span><br><span class="line">196</span><br><span class="line">197</span><br><span class="line">198</span><br><span class="line">199</span><br><span class="line">200</span><br><span class="line">201</span><br><span class="line">202</span><br><span class="line">203</span><br><span class="line">204</span><br><span class="line">205</span><br><span class="line">206</span><br><span class="line">207</span><br><span class="line">208</span><br><span class="line">209</span><br><span class="line">210</span><br><span class="line">211</span><br><span class="line">212</span><br><span class="line">213</span><br><span class="line">214</span><br><span class="line">215</span><br><span class="line">216</span><br><span class="line">217</span><br></pre></td><td class="code"><pre><span class="line">@@ <span class="number">-2</span>,<span class="number">6</span> +<span class="number">2</span>,<span class="number">7</span> @@</span><br><span class="line"> <span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><stdio.h></span></span></span><br><span class="line"> <span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><stdlib.h></span></span></span><br><span class="line"> <span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><string.h></span></span></span><br><span class="line">+<span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><stdint.h></span></span></span><br><span class="line"></span><br><span class="line"> <span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line"> <span class="keyword">char</span>* buffer;</span><br><span class="line">@@ <span class="number">-10</span>,<span class="number">6</span> +<span class="number">11</span>,<span class="number">105</span> @@ <span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line"> } InputBuffer;</span><br><span class="line"></span><br><span class="line">+<span class="keyword">typedef</span> <span class="keyword">enum</span> { EXECUTE_SUCCESS, EXECUTE_TABLE_FULL } ExecuteResult;</span><br><span class="line">+</span><br><span class="line">+<span class="keyword">typedef</span> <span class="keyword">enum</span> {</span><br><span class="line">+ META_COMMAND_SUCCESS,</span><br><span class="line">+ META_COMMAND_UNRECOGNIZED_COMMAND</span><br><span class="line">+} MetaCommandResult;</span><br><span class="line">+</span><br><span class="line">+<span class="keyword">typedef</span> <span class="keyword">enum</span> {</span><br><span class="line">+ PREPARE_SUCCESS,</span><br><span class="line">+ PREPARE_SYNTAX_ERROR,</span><br><span class="line">+ PREPARE_UNRECOGNIZED_STATEMENT</span><br><span class="line">+ } PrepareResult;</span><br><span class="line">+</span><br><span class="line">+<span class="keyword">typedef</span> <span class="keyword">enum</span> { STATEMENT_INSERT, STATEMENT_SELECT } StatementType;</span><br><span class="line">+</span><br><span class="line">+<span class="meta">#<span class="meta-keyword">define</span> COLUMN_USERNAME_SIZE 32</span></span><br><span class="line">+<span class="meta">#<span class="meta-keyword">define</span> COLUMN_EMAIL_SIZE 255</span></span><br><span class="line">+<span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line">+ <span class="keyword">uint32_t</span> id;</span><br><span class="line">+ <span class="keyword">char</span> username[COLUMN_USERNAME_SIZE];</span><br><span class="line">+ <span class="keyword">char</span> email[COLUMN_EMAIL_SIZE];</span><br><span class="line">+} Row;</span><br><span class="line">+</span><br><span class="line">+<span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line">+ StatementType type;</span><br><span class="line">+ Row row_to_insert; <span class="comment">//only used by insert statement</span></span><br><span class="line">+} Statement;</span><br><span class="line">+</span><br><span class="line">+<span class="meta">#<span class="meta-keyword">define</span> size_of_attribute(Struct, Attribute) sizeof(((Struct*)0)->Attribute)</span></span><br><span class="line">+</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> ID_SIZE = size_of_attribute(Row, id);</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> USERNAME_SIZE = size_of_attribute(Row, username);</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> EMAIL_SIZE = size_of_attribute(Row, email);</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> ID_OFFSET = <span class="number">0</span>;</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> USERNAME_OFFSET = ID_OFFSET + ID_SIZE;</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> EMAIL_OFFSET = USERNAME_OFFSET + USERNAME_SIZE;</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> ROW_SIZE = ID_SIZE + USERNAME_SIZE + EMAIL_SIZE;</span><br><span class="line">+</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> PAGE_SIZE = <span class="number">4096</span>;</span><br><span class="line">+<span class="meta">#<span class="meta-keyword">define</span> TABLE_MAX_PAGES 100</span></span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> ROWS_PER_PAGE = PAGE_SIZE / ROW_SIZE;</span><br><span class="line">+<span class="keyword">const</span> <span class="keyword">uint32_t</span> TABLE_MAX_ROWS = ROWS_PER_PAGE * TABLE_MAX_PAGES;</span><br><span class="line">+</span><br><span class="line">+<span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line">+ <span class="keyword">uint32_t</span> num_rows;</span><br><span class="line">+ <span class="keyword">void</span>* pages[TABLE_MAX_PAGES];</span><br><span class="line">+} Table;</span><br><span class="line">+</span><br><span class="line">+<span class="function"><span class="keyword">void</span> <span class="title">print_row</span><span class="params">(Row* row)</span> </span>{</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"(%d, %s, %s)\n"</span>, row->id, row->username, row->email);</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function"><span class="keyword">void</span> <span class="title">serialize_row</span><span class="params">(Row* source, <span class="keyword">void</span>* destination)</span> </span>{</span><br><span class="line">+ <span class="built_in">memcpy</span>(destination + ID_OFFSET, &(source->id), ID_SIZE);</span><br><span class="line">+ <span class="built_in">memcpy</span>(destination + USERNAME_OFFSET, &(source->username), USERNAME_SIZE);</span><br><span class="line">+ <span class="built_in">memcpy</span>(destination + EMAIL_OFFSET, &(source->email), EMAIL_SIZE);</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function"><span class="keyword">void</span> <span class="title">deserialize_row</span><span class="params">(<span class="keyword">void</span> *source, Row* destination)</span> </span>{</span><br><span class="line">+ <span class="built_in">memcpy</span>(&(destination->id), source + ID_OFFSET, ID_SIZE);</span><br><span class="line">+ <span class="built_in">memcpy</span>(&(destination->username), source + USERNAME_OFFSET, USERNAME_SIZE);</span><br><span class="line">+ <span class="built_in">memcpy</span>(&(destination->email), source + EMAIL_OFFSET, EMAIL_SIZE);</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function"><span class="keyword">void</span>* <span class="title">row_slot</span><span class="params">(Table* table, <span class="keyword">uint32_t</span> row_num)</span> </span>{</span><br><span class="line">+ <span class="keyword">uint32_t</span> page_num = row_num / ROWS_PER_PAGE;</span><br><span class="line">+ <span class="keyword">void</span> *page = table->pages[page_num];</span><br><span class="line">+ <span class="keyword">if</span> (page == <span class="literal">NULL</span>) {</span><br><span class="line">+ <span class="comment">// Allocate memory only when we try to access page</span></span><br><span class="line">+ page = table->pages[page_num] = <span class="built_in">malloc</span>(PAGE_SIZE);</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">uint32_t</span> row_offset = row_num % ROWS_PER_PAGE;</span><br><span class="line">+ <span class="keyword">uint32_t</span> byte_offset = row_offset * ROW_SIZE;</span><br><span class="line">+ <span class="keyword">return</span> page + byte_offset;</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function">Table* <span class="title">new_table</span><span class="params">()</span> </span>{</span><br><span class="line">+ Table* table = <span class="built_in">malloc</span>(<span class="keyword">sizeof</span>(Table));</span><br><span class="line">+ table->num_rows = <span class="number">0</span>;</span><br><span class="line">+ <span class="keyword">for</span> (<span class="keyword">uint32_t</span> i = <span class="number">0</span>; i < TABLE_MAX_PAGES; i++) {</span><br><span class="line">+ table->pages[i] = <span class="literal">NULL</span>;</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">return</span> table;</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function"><span class="keyword">void</span> <span class="title">free_table</span><span class="params">(Table* table)</span> </span>{</span><br><span class="line">+ <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; table->pages[i]; i++) {</span><br><span class="line">+ <span class="built_in">free</span>(table->pages[i]);</span><br><span class="line">+ }</span><br><span class="line">+ <span class="built_in">free</span>(table);</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line"> <span class="function">InputBuffer* <span class="title">new_input_buffer</span><span class="params">()</span> </span>{</span><br><span class="line"> InputBuffer* input_buffer = <span class="built_in">malloc</span>(<span class="keyword">sizeof</span>(InputBuffer));</span><br><span class="line"> input_buffer->buffer = <span class="literal">NULL</span>;</span><br><span class="line">@@ <span class="number">-40</span>,<span class="number">17</span> +<span class="number">140</span>,<span class="number">105</span> @@ <span class="function"><span class="keyword">void</span> <span class="title">close_input_buffer</span><span class="params">(InputBuffer* input_buffer)</span> </span>{</span><br><span class="line"> <span class="built_in">free</span>(input_buffer);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line">+<span class="function">MetaCommandResult <span class="title">do_meta_command</span><span class="params">(InputBuffer* input_buffer, Table *table)</span> </span>{</span><br><span class="line">+ <span class="keyword">if</span> (<span class="built_in">strcmp</span>(input_buffer->buffer, <span class="string">".exit"</span>) == <span class="number">0</span>) {</span><br><span class="line">+ close_input_buffer(input_buffer);</span><br><span class="line">+ free_table(table);</span><br><span class="line">+ <span class="built_in">exit</span>(EXIT_SUCCESS);</span><br><span class="line">+ } <span class="keyword">else</span> {</span><br><span class="line">+ <span class="keyword">return</span> META_COMMAND_UNRECOGNIZED_COMMAND;</span><br><span class="line">+ }</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function">PrepareResult <span class="title">prepare_statement</span><span class="params">(InputBuffer* input_buffer,</span></span></span><br><span class="line"><span class="function"><span class="params">+ Statement* statement)</span> </span>{</span><br><span class="line">+ <span class="keyword">if</span> (<span class="built_in">strncmp</span>(input_buffer->buffer, <span class="string">"insert"</span>, <span class="number">6</span>) == <span class="number">0</span>) {</span><br><span class="line">+ statement->type = STATEMENT_INSERT;</span><br><span class="line">+ <span class="keyword">int</span> args_assigned = <span class="built_in">sscanf</span>(</span><br><span class="line">+ input_buffer->buffer, <span class="string">"insert %d %s %s"</span>, &(statement->row_to_insert.id),</span><br><span class="line">+ statement->row_to_insert.username, statement->row_to_insert.email</span><br><span class="line">+ );</span><br><span class="line">+ <span class="keyword">if</span> (args_assigned < <span class="number">3</span>) {</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_SYNTAX_ERROR;</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_SUCCESS;</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">if</span> (<span class="built_in">strcmp</span>(input_buffer->buffer, <span class="string">"select"</span>) == <span class="number">0</span>) {</span><br><span class="line">+ statement->type = STATEMENT_SELECT;</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_SUCCESS;</span><br><span class="line">+ }</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_UNRECOGNIZED_STATEMENT;</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function">ExecuteResult <span class="title">execute_insert</span><span class="params">(Statement* statement, Table* table)</span> </span>{</span><br><span class="line">+ <span class="keyword">if</span> (table->num_rows >= TABLE_MAX_ROWS) {</span><br><span class="line">+ <span class="keyword">return</span> EXECUTE_TABLE_FULL;</span><br><span class="line">+ }</span><br><span class="line">+</span><br><span class="line">+ Row* row_to_insert = &(statement->row_to_insert);</span><br><span class="line">+</span><br><span class="line">+ serialize_row(row_to_insert, row_slot(table, table->num_rows));</span><br><span class="line">+ table->num_rows += <span class="number">1</span>;</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">return</span> EXECUTE_SUCCESS;</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function">ExecuteResult <span class="title">execute_select</span><span class="params">(Statement* statement, Table* table)</span> </span>{</span><br><span class="line">+ Row row;</span><br><span class="line">+ <span class="keyword">for</span> (<span class="keyword">uint32_t</span> i = <span class="number">0</span>; i < table->num_rows; i++) {</span><br><span class="line">+ deserialize_row(row_slot(table, i), &row);</span><br><span class="line">+ print_row(&row);</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">return</span> EXECUTE_SUCCESS;</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function">ExecuteResult <span class="title">execute_statement</span><span class="params">(Statement* statement, Table *table)</span> </span>{</span><br><span class="line">+ <span class="keyword">switch</span> (statement->type) {</span><br><span class="line">+ <span class="keyword">case</span> (STATEMENT_INSERT):</span><br><span class="line">+ <span class="keyword">return</span> execute_insert(statement, table);</span><br><span class="line">+ <span class="keyword">case</span> (STATEMENT_SELECT):</span><br><span class="line">+ <span class="keyword">return</span> execute_select(statement, table);</span><br><span class="line">+ }</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line"> <span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">(<span class="keyword">int</span> argc, <span class="keyword">char</span>* argv[])</span> </span>{</span><br><span class="line">+ Table* table = new_table();</span><br><span class="line"> InputBuffer* input_buffer = new_input_buffer();</span><br><span class="line"> <span class="keyword">while</span> (<span class="literal">true</span>) {</span><br><span class="line"> print_prompt();</span><br><span class="line"> read_input(input_buffer);</span><br><span class="line"></span><br><span class="line">- <span class="keyword">if</span> (<span class="built_in">strcmp</span>(input_buffer->buffer, <span class="string">".exit"</span>) == <span class="number">0</span>) {</span><br><span class="line">- close_input_buffer(input_buffer);</span><br><span class="line">- <span class="built_in">exit</span>(EXIT_SUCCESS);</span><br><span class="line">- } <span class="keyword">else</span> {</span><br><span class="line">- <span class="built_in">printf</span>(<span class="string">"Unrecognized command '%s'.\n"</span>, input_buffer->buffer);</span><br><span class="line">+ <span class="keyword">if</span> (input_buffer->buffer[<span class="number">0</span>] == <span class="string">'.'</span>) {</span><br><span class="line">+ <span class="keyword">switch</span> (do_meta_command(input_buffer, table)) {</span><br><span class="line">+ <span class="keyword">case</span> (META_COMMAND_SUCCESS):</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line">+ <span class="keyword">case</span> (META_COMMAND_UNRECOGNIZED_COMMAND):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Unrecognized command '%s'\n"</span>, input_buffer->buffer);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line">+ }</span><br><span class="line">+ }</span><br><span class="line">+</span><br><span class="line">+ Statement statement;</span><br><span class="line">+ <span class="keyword">switch</span> (prepare_statement(input_buffer, &statement)) {</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_SUCCESS):</span><br><span class="line">+ <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_SYNTAX_ERROR):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Syntax error. Could not parse statement.\n"</span>);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_UNRECOGNIZED_STATEMENT):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Unrecognized keyword at start of '%s'.\n"</span>,</span><br><span class="line">+ input_buffer->buffer);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line">+ }</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">switch</span> (execute_statement(&statement, table)) {</span><br><span class="line">+ <span class="keyword">case</span> (EXECUTE_SUCCESS):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Executed.\n"</span>);</span><br><span class="line">+ <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">case</span> (EXECUTE_TABLE_FULL):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Error: Table full.\n"</span>);</span><br><span class="line">+ <span class="keyword">break</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
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<a href="/2021/04/12/057-travis-troubleshooting/" class="post-title-link" itemprop="url">hexo next 主题通过 travis ci 执行 hexo generate 报错</a>
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<h2 id="问题记录"><a href="#问题记录" class="headerlink" title="问题记录"></a>问题记录</h2><p>前段时间给 github page 换了一个 hexo 主题，换成了 <a href="https://theme-next.iissnan.com/" target="_blank" rel="noopener">next</a> 主题，但是在更换主题之后，发现 travis 上的 CI 无法跑过了，查看日志内容如下:</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> node --version</span><br><span class="line">v6.9.4</span><br><span class="line"><span class="meta">$</span> npm --version</span><br><span class="line">3.10.10</span><br><span class="line"><span class="meta">$</span> nvm --version</span><br><span class="line">0.37.2</span><br><span class="line">before_install.1</span><br><span class="line">0.01s$ export TZ='Asia/Shanghai'</span><br><span class="line">before_install.2</span><br><span class="line">6.90s$ npm install -g hexo</span><br><span class="line">before_install.3</span><br><span class="line">2.81s$ npm install -g hexo-cli</span><br><span class="line">install</span><br><span class="line">1.54s$ npm install</span><br><span class="line">before_script.1</span><br><span class="line">0.01s$ git config --global user.name "Win-Man"</span><br><span class="line">before_script.2</span><br><span class="line">0.00s$ git config --global user.email [email protected]</span><br><span class="line">before_script.3</span><br><span class="line">0.00s$ sed -i'' "[email protected]:Win-Man/win-man.github.io.git~https://${CI_TOKEN}@github.com/Win-Man/win-man.github.io.git~" _config.yml</span><br><span class="line">0.67s$ hexo clean</span><br><span class="line">The command "hexo clean" exited with 0.</span><br><span class="line">1.17s$ hexo generate</span><br><span class="line">INFO Start processing</span><br><span class="line">FATAL Something's wrong. Maybe you can find the solution here: https://hexo.io/docs/troubleshooting.html</span><br><span class="line">TypeError: Object.values is not a function</span><br><span class="line"> at points.views.forEach.type (/home/travis/build/Win-Man/win-man.github.io/themes/next/scripts/events/lib/injects.js:82:46)</span><br><span class="line"> at Array.forEach (native)</span><br><span class="line"> at module.exports.hexo (/home/travis/build/Win-Man/win-man.github.io/themes/next/scripts/events/lib/injects.js:67:16)</span><br><span class="line"> at Hexo.hexo.on (/home/travis/build/Win-Man/win-man.github.io/themes/next/scripts/events/index.js:9:27)</span><br><span class="line"> at emitNone (events.js:86:13)</span><br><span class="line"> at Hexo.emit (events.js:185:7)</span><br><span class="line"> at Hexo._generate (/home/travis/build/Win-Man/win-man.github.io/node_modules/hexo/lib/hexo/index.js:399:8)</span><br><span class="line"> at loadDatabase.then.then (/home/travis/build/Win-Man/win-man.github.io/node_modules/hexo/lib/hexo/index.js:249:22)</span><br><span class="line"> at tryCatcher (/home/travis/build/Win-Man/win-man.github.io/node_modules/bluebird/js/release/util.js:16:23)</span><br><span class="line"> at Promise._settlePromiseFromHandler (/home/travis/build/Win-Man/win-man.github.io/node_modules/bluebird/js/release/promise.js:547:31)</span><br><span class="line"> at Promise._settlePromise (/home/travis/build/Win-Man/win-man.github.io/node_modules/bluebird/js/release/promise.js:604:18)</span><br><span class="line"> at Promise._settlePromise0 (/home/travis/build/Win-Man/win-man.github.io/node_modules/bluebird/js/release/promise.js:649:10)</span><br><span class="line"> at Promise._settlePromises (/home/travis/build/Win-Man/win-man.github.io/node_modules/bluebird/js/release/promise.js:729:18)</span><br><span class="line"> at Promise._fulfill (/home/travis/build/Win-Man/win-man.github.io/node_modules/bluebird/js/release/promise.js:673:18)</span><br><span class="line"> at PromiseArray._resolve (/home/travis/build/Win-Man/win-man.github.io/node_modules/bluebird/js/release/promise_array.js:127:19)</span><br><span class="line"> at PromiseArray._promiseFulfilled (/home/travis/build/Win-Man/win-man.github.io/node_modules/bluebird/js/release/promise_array.js:145:14)</span><br><span class="line"> at Promise._settlePromise (/home/travis/build/Win-Man/win-man.github.io/node_modules/bluebird/js/release/promise.js:609:26)</span><br><span class="line">The command "hexo generate" exited with 2.</span><br><span class="line">cache.2</span><br><span class="line">store build cache</span><br></pre></td></tr></table></figure>
<p>但是在我本地电脑执行 <code>hexo g</code>,<code>hexo s</code>,<code>hexo d</code> 都没啥问题，怀疑到了 node js 版本的问题，因为这个 repo 中的 <code>.travis.yml</code> 配置文件还是好几年前的了，于是尝试修改 node js 版本与本地版本一致。修改版本并提交之后还是有报错，但是报错信息变了。</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">$</span> node --version</span><br><span class="line">v13.11.0</span><br><span class="line"><span class="meta">$</span> npm --version</span><br><span class="line">6.13.7</span><br><span class="line"><span class="meta">$</span> nvm --version</span><br><span class="line">0.37.2</span><br><span class="line">before_install.1</span><br><span class="line">0.01s$ export TZ='Asia/Shanghai'</span><br><span class="line">before_install.2</span><br><span class="line">5.40s$ npm install -g hexo</span><br><span class="line">3.16s$ npm install -g hexo-cli</span><br><span class="line">npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@~2.3.1 (node_modules/hexo-cli/node_modules/chokidar/node_modules/fsevents):</span><br><span class="line">npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for [email protected]: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})</span><br><span class="line">npm ERR! code EEXIST</span><br><span class="line">npm ERR! syscall symlink</span><br><span class="line">npm ERR! path ../lib/node_modules/hexo-cli/bin/hexo</span><br><span class="line">npm ERR! dest /home/travis/.nvm/versions/node/v13.11.0/bin/hexo</span><br><span class="line">npm ERR! errno -17</span><br><span class="line">npm ERR! EEXIST: file already exists, symlink '../lib/node_modules/hexo-cli/bin/hexo' -> '/home/travis/.nvm/versions/node/v13.11.0/bin/hexo'</span><br><span class="line">npm ERR! File exists: /home/travis/.nvm/versions/node/v13.11.0/bin/hexo</span><br><span class="line">npm ERR! Remove the existing file and try again, or run npm</span><br><span class="line">npm ERR! with --force to overwrite files recklessly.</span><br><span class="line">npm ERR! A complete log of this run can be found in:</span><br><span class="line">npm ERR! /home/travis/.npm/_logs/2021-04-12T06_49_56_362Z-debug.log</span><br><span class="line">The command "npm install -g hexo-cli" failed and exited with 239 during .</span><br></pre></td></tr></table></figure>
<p>根据错误信息查找到一个链接<br><a href="https://segmentfault.com/a/1190000018759308" target="_blank" rel="noopener">https://segmentfault.com/a/1190000018759308</a></p>
<h2 id="解决方案"><a href="#解决方案" class="headerlink" title="解决方案"></a>解决方案</h2><p>参考链接中的结果方案在 <code>npm install</code> 中加上 <code>-f</code> 选项。<br>附上完整的 <code>.travis.yml</code> 内容:</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line">language: node_js</span><br><span class="line">node_js:</span><br><span class="line">- '13.11.0'</span><br><span class="line">branches:</span><br><span class="line"> only:</span><br><span class="line"> - dev</span><br><span class="line">cache:</span><br><span class="line"> directories:</span><br><span class="line"> - node_modules</span><br><span class="line">before_install:</span><br><span class="line">- export TZ='Asia/Shanghai'</span><br><span class="line">- npm install -g hexo</span><br><span class="line">- npm install -g hexo-cli -f</span><br><span class="line">before_script:</span><br><span class="line">- git config --global user.name "Win-Man"</span><br><span class="line">- git config --global user.email [email protected]</span><br><span class="line">- sed -i'' "[email protected]:Win-Man/win-man.github.io.git~https://${CI_TOKEN}@github.com/Win-Man/win-man.github.io.git~" _config.yml</span><br><span class="line">install:</span><br><span class="line">- npm install -f</span><br><span class="line">script:</span><br><span class="line">- hexo clean</span><br><span class="line">- hexo generate</span><br><span class="line">after_success:</span><br><span class="line">- hexo deploy</span><br></pre></td></tr></table></figure>
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<a href="/2021/04/11/056-simple-database-2/" class="post-title-link" itemprop="url">Let's Build a Simple Database - World's Simplest SQL Compiler and Virtual Machine</a>
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<p>原文地址：<a href="https://cstack.github.io/db_tutorial/parts/part2.html" target="_blank" rel="noopener">https://cstack.github.io/db_tutorial/parts/part2.html</a><br>原文作者： <a href="https://github.com/cstack" target="_blank" rel="noopener">cstack</a><br>译者：<a href="https://github.com/Win-Man" target="_blank" rel="noopener">Win-Man</a></p>
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<h2 id="世界上最简单的-SQL-编译器和字节码虚拟机"><a href="#世界上最简单的-SQL-编译器和字节码虚拟机" class="headerlink" title="世界上最简单的 SQL 编译器和字节码虚拟机"></a>世界上最简单的 SQL 编译器和字节码虚拟机</h2><p>我们正在写一个 sqlite 的克隆版本。sqlite 中 SQL 编译器是一个解析一个 string 输入并输出一个内部可识别的字节码。然后 sqlite 编译之后的字节码传给字节码虚拟机，在虚拟机中执行 SQL。</p>
<p><img src="https://cstack.github.io/db_tutorial/assets/images/arch2.gif" alt></p>
<p><center>SQLite Architecture (<a href="https://www.sqlite.org/arch.html" target="_blank" rel="noopener">https://www.sqlite.org/arch.html</a>)<center></center></center></p>
<p>将这些内容拆成两个步骤有一些优势点：</p>
<ul>
<li>减少每个部门的复杂度（例如：字节码虚拟机不用考虑语法错误）</li>
<li>对于相同的查询可以只需要编译一次，将编译后的字节码缓存住，以此可以提高性能</li>
</ul>
<p>基于这个想法，我们重构一下我们的主函数来支持两个新的关键字：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">(<span class="keyword">int</span> argc, <span class="keyword">char</span>* argv[])</span> </span>{</span><br><span class="line"> InputBuffer* input_buffer = new_input_buffer();</span><br><span class="line"> <span class="keyword">while</span> (<span class="literal">true</span>) {</span><br><span class="line"> print_prompt();</span><br><span class="line"> read_input(input_buffer);</span><br><span class="line"></span><br><span class="line">- <span class="keyword">if</span> (<span class="built_in">strcmp</span>(input_buffer->buffer, <span class="string">".exit"</span>) == <span class="number">0</span>) {</span><br><span class="line">- <span class="built_in">exit</span>(EXIT_SUCCESS);</span><br><span class="line">- } <span class="keyword">else</span> {</span><br><span class="line">- <span class="built_in">printf</span>(<span class="string">"Unrecognized command '%s'.\n"</span>, input_buffer->buffer);</span><br><span class="line">+ <span class="keyword">if</span> (input_buffer->buffer[<span class="number">0</span>] == <span class="string">'.'</span>) {</span><br><span class="line">+ <span class="keyword">switch</span> (do_meta_command(input_buffer)) {</span><br><span class="line">+ <span class="keyword">case</span> (META_COMMAND_SUCCESS):</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line">+ <span class="keyword">case</span> (META_COMMAND_UNRECOGNIZED_COMMAND):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Unrecognized command '%s'\n"</span>, input_buffer->buffer);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line">+ }</span><br><span class="line"> }</span><br><span class="line">+</span><br><span class="line">+ Statement statement;</span><br><span class="line">+ <span class="keyword">switch</span> (prepare_statement(input_buffer, &statement)) {</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_SUCCESS):</span><br><span class="line">+ <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_UNRECOGNIZED_STATEMENT):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Unrecognized keyword at start of '%s'.\n"</span>,</span><br><span class="line">+ input_buffer->buffer);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line">+ }</span><br><span class="line">+</span><br><span class="line">+ execute_statement(&statement);</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Executed.\n"</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<p>像 <code>.exit</code> 这种非 SQL 的语句被称为“元指令”。这些元指令都是以 <code>.</code> 开始的，所以我们可以将这类语句单独在一个独立的函数中处理。</p>
<p>接下来，我们增加一个步骤用于将输入的行转换为数据库内部表达式。这就是我们对于 sqlite 前端的 hack 版本。</p>
<p>最后，我们将预处理好的语句传递给 <code>execute_statement</code>。这个函数后续会演进成我们的字节码虚拟机。</p>
<p>需要需要的是我们新增加了两个函数，并且这两个函数返回 enum 来表示成功或者失败。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">typedef</span> <span class="keyword">enum</span> {</span><br><span class="line"> META_COMMAND_SUCCESS,</span><br><span class="line"> META_COMMAND_UNRECOGNIZED_COMMAND</span><br><span class="line">} MetaCommandResult;</span><br><span class="line"></span><br><span class="line"><span class="keyword">typedef</span> <span class="keyword">enum</span> { PREPARE_SUCCESS, PREPARE_UNRECOGNIZED_STATEMENT } PrepareResult;</span><br></pre></td></tr></table></figure>
<p>“Unrecognized statement” 语句表示这个语句像是一个表达式，但是表达式有错误，所以我们在任何情况都使用 enum 枚举结果代码。C 语言的编译器会报错如果我的 switch 语句不能处理枚举的项，所以我们可以确保处理了这个函数的每个结果。在将来可能会添加更多的结果代码。</p>
<p><code>do_meta_command</code> 只是现有函数的一个封装，为了之后可处理更多的命令：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="function">MetaCommandResult <span class="title">do_meta_command</span><span class="params">(InputBuffer* input_buffer)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (<span class="built_in">strcmp</span>(input_buffer->buffer, <span class="string">".exit"</span>) == <span class="number">0</span>) {</span><br><span class="line"> <span class="built_in">exit</span>(EXIT_SUCCESS);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">return</span> META_COMMAND_UNRECOGNIZED_COMMAND;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>目前我们的预处理语句只是包含了有两个可能结果的枚举数组。这可能会包含更多的数据如果我们允许在语句中传入参数:</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">typedef</span> <span class="keyword">enum</span> { STATEMENT_INSERT, STATEMENT_SELECT } StatementType;</span><br><span class="line"></span><br><span class="line"><span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line"> StatementType type;</span><br><span class="line">} Statement;</span><br></pre></td></tr></table></figure>
<p><code>prepare_statement</code>（我们的 SQL 编译器）目前还无法识别 SQL 语句。事实上这个函数只能识别两个单词：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">PrepareResult prepare_statement(InputBuffer* input_buffer,</span><br><span class="line"> Statement* statement) {</span><br><span class="line"> if (strncmp(input_buffer->buffer, "insert", 6) == 0) {</span><br><span class="line"> statement->type = STATEMENT_INSERT;</span><br><span class="line"> return PREPARE_SUCCESS;</span><br><span class="line"> }</span><br><span class="line"> if (strcmp(input_buffer->buffer, "select") == 0) {</span><br><span class="line"> statement->type = STATEMENT_SELECT;</span><br><span class="line"> return PREPARE_SUCCESS;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> return PREPARE_UNRECOGNIZED_STATEMENT;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>需要注意的是我们使用 strncmp 对比 insert 因为 insert 关键字之后会跟着插入的数据。（例如：insert 1 cstack <a href="mailto:[email protected]" target="_blank" rel="noopener">[email protected]</a>）</p>
<p>最后，<code>execute_statement</code> 包含了一些分支：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">execute_statement</span><span class="params">(Statement* statement)</span> </span>{</span><br><span class="line"> <span class="keyword">switch</span> (statement->type) {</span><br><span class="line"> <span class="keyword">case</span> (STATEMENT_INSERT):</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"This is where we would do an insert.\n"</span>);</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> <span class="keyword">case</span> (STATEMENT_SELECT):</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"This is where we would do a select.\n"</span>);</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>这边并没有返回任何错误码因为目前为止这边还不会发生任何错误。</p>
<p>经过这些重构之后，我们现在的 sqlite 可以认识两个新的关键字。</p>
<figure class="highlight sql"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">~ ./db</span><br><span class="line">db > insert foo bar</span><br><span class="line">This is where we would <span class="keyword">do</span> an insert.</span><br><span class="line">Executed.</span><br><span class="line">db > <span class="keyword">delete</span> foo</span><br><span class="line">Unrecognized keyword <span class="keyword">at</span> <span class="keyword">start</span> <span class="keyword">of</span> <span class="string">'delete foo'</span>.</span><br><span class="line">db > <span class="keyword">select</span></span><br><span class="line">This <span class="keyword">is</span> <span class="keyword">where</span> we would <span class="keyword">do</span> a select.</span><br><span class="line">Executed.</span><br><span class="line">db > .tables</span><br><span class="line">Unrecognized command <span class="string">'.tables'</span></span><br><span class="line">db > .exit</span><br><span class="line">~</span><br></pre></td></tr></table></figure>
<p>我们数据库的基本框架基本已经形成了，如果不用存储数据的话，这是不是很好？在下一个部分，我们会去实现 insert 和 select 语句，创造世界上最差劲的存储引擎。同时在这给出这一差异部分的内容：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br></pre></td><td class="code"><pre><span class="line">@@ <span class="number">-10</span>,<span class="number">6</span> +<span class="number">10</span>,<span class="number">23</span> @@ <span class="class"><span class="keyword">struct</span> <span class="title">InputBuffer_t</span> {</span></span><br><span class="line"> } InputBuffer;</span><br><span class="line"> </span><br><span class="line">+<span class="keyword">typedef</span> <span class="keyword">enum</span> {</span><br><span class="line">+ META_COMMAND_SUCCESS,</span><br><span class="line">+ META_COMMAND_UNRECOGNIZED_COMMAND</span><br><span class="line">+} MetaCommandResult;</span><br><span class="line">+</span><br><span class="line">+<span class="keyword">typedef</span> <span class="keyword">enum</span> { PREPARE_SUCCESS, PREPARE_UNRECOGNIZED_STATEMENT } PrepareResult;</span><br><span class="line">+</span><br><span class="line">+<span class="keyword">typedef</span> <span class="keyword">enum</span> { STATEMENT_INSERT, STATEMENT_SELECT } StatementType;</span><br><span class="line">+</span><br><span class="line">+<span class="keyword">typedef</span> <span class="class"><span class="keyword">struct</span> {</span></span><br><span class="line">+ StatementType type;</span><br><span class="line">+} Statement;</span><br><span class="line">+</span><br><span class="line"> <span class="function">InputBuffer* <span class="title">new_input_buffer</span><span class="params">()</span> </span>{</span><br><span class="line"> InputBuffer* input_buffer = <span class="built_in">malloc</span>(<span class="keyword">sizeof</span>(InputBuffer));</span><br><span class="line"> input_buffer->buffer = <span class="literal">NULL</span>;</span><br><span class="line">@@ <span class="number">-40</span>,<span class="number">17</span> +<span class="number">57</span>,<span class="number">67</span> @@ <span class="function"><span class="keyword">void</span> <span class="title">close_input_buffer</span><span class="params">(InputBuffer* input_buffer)</span> </span>{</span><br><span class="line"> <span class="built_in">free</span>(input_buffer);</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line">+<span class="function">MetaCommandResult <span class="title">do_meta_command</span><span class="params">(InputBuffer* input_buffer)</span> </span>{</span><br><span class="line">+ <span class="keyword">if</span> (<span class="built_in">strcmp</span>(input_buffer->buffer, <span class="string">".exit"</span>) == <span class="number">0</span>) {</span><br><span class="line">+ close_input_buffer(input_buffer);</span><br><span class="line">+ <span class="built_in">exit</span>(EXIT_SUCCESS);</span><br><span class="line">+ } <span class="keyword">else</span> {</span><br><span class="line">+ <span class="keyword">return</span> META_COMMAND_UNRECOGNIZED_COMMAND;</span><br><span class="line">+ }</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function">PrepareResult <span class="title">prepare_statement</span><span class="params">(InputBuffer* input_buffer,</span></span></span><br><span class="line"><span class="function"><span class="params">+ Statement* statement)</span> </span>{</span><br><span class="line">+ <span class="keyword">if</span> (<span class="built_in">strncmp</span>(input_buffer->buffer, <span class="string">"insert"</span>, <span class="number">6</span>) == <span class="number">0</span>) {</span><br><span class="line">+ statement->type = STATEMENT_INSERT;</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_SUCCESS;</span><br><span class="line">+ }</span><br><span class="line">+ <span class="keyword">if</span> (<span class="built_in">strcmp</span>(input_buffer->buffer, <span class="string">"select"</span>) == <span class="number">0</span>) {</span><br><span class="line">+ statement->type = STATEMENT_SELECT;</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_SUCCESS;</span><br><span class="line">+ }</span><br><span class="line">+</span><br><span class="line">+ <span class="keyword">return</span> PREPARE_UNRECOGNIZED_STATEMENT;</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line">+<span class="function"><span class="keyword">void</span> <span class="title">execute_statement</span><span class="params">(Statement* statement)</span> </span>{</span><br><span class="line">+ <span class="keyword">switch</span> (statement->type) {</span><br><span class="line">+ <span class="keyword">case</span> (STATEMENT_INSERT):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"This is where we would do an insert.\n"</span>);</span><br><span class="line">+ <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">case</span> (STATEMENT_SELECT):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"This is where we would do a select.\n"</span>);</span><br><span class="line">+ <span class="keyword">break</span>;</span><br><span class="line">+ }</span><br><span class="line">+}</span><br><span class="line">+</span><br><span class="line"> <span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">(<span class="keyword">int</span> argc, <span class="keyword">char</span>* argv[])</span> </span>{</span><br><span class="line"> InputBuffer* input_buffer = new_input_buffer();</span><br><span class="line"> <span class="keyword">while</span> (<span class="literal">true</span>) {</span><br><span class="line"> print_prompt();</span><br><span class="line"> read_input(input_buffer);</span><br><span class="line"> </span><br><span class="line">- <span class="keyword">if</span> (<span class="built_in">strcmp</span>(input_buffer->buffer, <span class="string">".exit"</span>) == <span class="number">0</span>) {</span><br><span class="line">- close_input_buffer(input_buffer);</span><br><span class="line">- <span class="built_in">exit</span>(EXIT_SUCCESS);</span><br><span class="line">- } <span class="keyword">else</span> {</span><br><span class="line">- <span class="built_in">printf</span>(<span class="string">"Unrecognized command '%s'.\n"</span>, input_buffer->buffer);</span><br><span class="line">+ <span class="keyword">if</span> (input_buffer->buffer[<span class="number">0</span>] == <span class="string">'.'</span>) {</span><br><span class="line">+ <span class="keyword">switch</span> (do_meta_command(input_buffer)) {</span><br><span class="line">+ <span class="keyword">case</span> (META_COMMAND_SUCCESS):</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line">+ <span class="keyword">case</span> (META_COMMAND_UNRECOGNIZED_COMMAND):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Unrecognized command '%s'\n"</span>, input_buffer->buffer);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line">+ }</span><br><span class="line"> }</span><br><span class="line">+</span><br><span class="line">+ Statement statement;</span><br><span class="line">+ <span class="keyword">switch</span> (prepare_statement(input_buffer, &statement)) {</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_SUCCESS):</span><br><span class="line">+ <span class="keyword">break</span>;</span><br><span class="line">+ <span class="keyword">case</span> (PREPARE_UNRECOGNIZED_STATEMENT):</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Unrecognized keyword at start of '%s'.\n"</span>,</span><br><span class="line">+ input_buffer->buffer);</span><br><span class="line">+ <span class="keyword">continue</span>;</span><br><span class="line">+ }</span><br><span class="line">+</span><br><span class="line">+ execute_statement(&statement);</span><br><span class="line">+ <span class="built_in">printf</span>(<span class="string">"Executed.\n"</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
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