import{_ as e,o as a,c as s,a as n,f as t}from"./app-d4806199.js";const o={},i=t(`<h1 id="运维工具" tabindex="-1"><a class="header-anchor" href="#运维工具" aria-hidden="true">#</a> 运维工具</h1><h2 id="运维命令" tabindex="-1"><a class="header-anchor" href="#运维命令" aria-hidden="true">#</a> 运维命令</h2><h3 id="flush" tabindex="-1"><a class="header-anchor" href="#flush" aria-hidden="true">#</a> FLUSH</h3><p>将指定存储组的内存缓存区 Memory Table 的数据持久化到磁盘上，并将数据文件封口。</p><p>注意：此命令客户端不需要手动调用，IoTDB 有 wal 保证数据安全，IoTDB 会选择合适的时机进行 flush。<br> 如果频繁调用 flush 会导致数据文件很小，降低查询性能。</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code>IoTDB<span class="token operator">&gt;</span> FLUSH 
IoTDB<span class="token operator">&gt;</span> FLUSH root<span class="token punctuation">.</span>ln
IoTDB<span class="token operator">&gt;</span> FLUSH root<span class="token punctuation">.</span>sg1<span class="token punctuation">,</span>root<span class="token punctuation">.</span>sg2
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="merge" tabindex="-1"><a class="header-anchor" href="#merge" aria-hidden="true">#</a> MERGE</h3><p>触发层级合并和乱序合并。当前 IoTDB 支持使用如下两种 SQL 手动触发数据文件的合并：</p><ul><li><code>MERGE</code> 先触发层级合并，等层级合并执行完后，再触发乱序合并。在乱序合并中，仅重写重复的 Chunk，整理速度快，但是最终磁盘会存在多余数据。</li><li><code>FULL MERGE</code> 先触发层级合并，等层级合并执行完后，再触发乱序合并。在乱序合并中，将需要合并的顺序和乱序文件的所有数据都重新写一份，整理速度慢，最终磁盘将不存在无用的数据。</li></ul><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code>IoTDB<span class="token operator">&gt;</span> <span class="token keyword">MERGE</span>
IoTDB<span class="token operator">&gt;</span> <span class="token keyword">FULL</span> <span class="token keyword">MERGE</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="clear-cache" tabindex="-1"><a class="header-anchor" href="#clear-cache" aria-hidden="true">#</a> CLEAR CACHE</h3><p>手动清除chunk, chunk metadata和timeseries metadata的缓存，在内存资源紧张时，可以通过此命令，释放查询时缓存所占的内存空间。</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code>IoTDB<span class="token operator">&gt;</span> CLEAR CACHE
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><h3 id="set-ststem-to-readonly-writable" tabindex="-1"><a class="header-anchor" href="#set-ststem-to-readonly-writable" aria-hidden="true">#</a> SET STSTEM TO READONLY / WRITABLE</h3><p>手动设置系统为只读或者可写入模式。</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code>IoTDB<span class="token operator">&gt;</span> <span class="token keyword">SET</span> SYSTEM <span class="token keyword">TO</span> READONLY
IoTDB<span class="token operator">&gt;</span> <span class="token keyword">SET</span> SYSTEM <span class="token keyword">TO</span> WRITABLE
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="schema-snapshot" tabindex="-1"><a class="header-anchor" href="#schema-snapshot" aria-hidden="true">#</a> SCHEMA SNAPSHOT</h3><p>为了加快 IoTDB 重启速度，用户可以手动触发创建 schema 的快照，从而避免服务器从 mlog 文件中恢复。此功能不支持使用模板、标签或对齐序列的场景。</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code>IoTDB<span class="token operator">&gt;</span> <span class="token keyword">CREATE</span> <span class="token keyword">SNAPSHOT</span> <span class="token keyword">FOR</span> <span class="token keyword">SCHEMA</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><h3 id="超时" tabindex="-1"><a class="header-anchor" href="#超时" aria-hidden="true">#</a> 超时</h3><p>IoTDB 支持 Session 超时和查询超时。</p><h4 id="session-超时" tabindex="-1"><a class="header-anchor" href="#session-超时" aria-hidden="true">#</a> Session 超时</h4><p>Session 超时控制何时关闭空闲 Session。空闲 Session 指在一段时间内没有发起任何操作的 Session。</p><p>Session 超时默认未开启。可以在配置文件中通过 <code>session_timeout_threshold</code> 参数进行配置。</p><h4 id="查询超时" tabindex="-1"><a class="header-anchor" href="#查询超时" aria-hidden="true">#</a> 查询超时</h4><p>对于执行时间过长的查询，IoTDB 将强行中断该查询，并抛出超时异常，如下所示：</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code>IoTDB<span class="token operator">&gt;</span> <span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">;</span>
Msg: <span class="token number">701</span> <span class="token keyword">Current</span> query <span class="token operator">is</span> <span class="token keyword">time</span> <span class="token keyword">out</span><span class="token punctuation">,</span> please <span class="token keyword">check</span> your statement <span class="token operator">or</span> <span class="token keyword">modify</span> timeout parameter<span class="token punctuation">.</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>系统默认的超时时间为 60000 ms，可以在配置文件中通过 <code>query_timeout_threshold</code> 参数进行自定义配置。</p><p>如果您使用 JDBC 或 Session，还支持对单个查询设置超时时间（单位为 ms）：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token class-name">IoTDBStatement</span><span class="token punctuation">)</span> statement<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">executeQuery</span><span class="token punctuation">(</span><span class="token class-name">String</span> sql<span class="token punctuation">,</span> <span class="token keyword">long</span> timeoutInMS<span class="token punctuation">)</span>
session<span class="token punctuation">.</span><span class="token function">executeQueryStatement</span><span class="token punctuation">(</span><span class="token class-name">String</span> sql<span class="token punctuation">,</span> <span class="token keyword">long</span> timeout<span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><blockquote><p>如果不配置超时时间参数或将超时时间设置为负数，将使用服务器端默认的超时时间。<br> 如果超时时间设置为0，则会禁用超时功能。</p></blockquote><h4 id="查询中止" tabindex="-1"><a class="header-anchor" href="#查询中止" aria-hidden="true">#</a> 查询中止</h4><p>除了被动地等待查询超时外，IoTDB 还支持主动地中止查询，命令为：</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">KILL</span> QUERY <span class="token operator">&lt;</span>queryId<span class="token operator">&gt;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>通过指定 <code>queryId</code> 可以中止指定的查询，而如果不指定 <code>queryId</code>，将中止所有正在执行的查询。</p><p>为了获取正在执行的查询 id，用户可以使用 <code>show query processlist</code> 命令，该命令将显示所有正在执行的查询列表，结果形式如下：</p><table><thead><tr><th>Time</th><th>queryId</th><th>statement</th></tr></thead><tbody><tr><td></td><td></td><td></td></tr></tbody></table><p>其中 statement 最大显示长度为 64 字符。对于超过 64 字符的查询语句，将截取部分进行显示。</p>`,38);function r(d,l){return a(),s("div",null,[n(`

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