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       </script><title>死区处理 | IoTDB Website</title><meta name="description" content="旋转门压缩 旋转门压缩（SDT）算法是一种死区处理算法。SDT 的计算复杂度较低，并使用线性趋势来表示大量数据。 在 IoTDB 中，SDT 在刷新到磁盘时会压缩并丢弃数据。 IoTDB 允许您在创建时间序列时指定 SDT 的属性，并支持以下三个属性： CompDev （Compression Deviation，压缩偏差）; CompDev 是 SD...">
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3 分钟</span><meta property="timeRequired" content="PT3M"></span><!----><!----></div><hr></div><div class="toc-place-holder"><aside id="toc"><!--[--><!----><!--]--><div class="toc-header">此页内容<button type="button" class="print-button" title="打印"><svg xmlns="http://www.w3.org/2000/svg" class="icon print-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="print icon"><path d="M819.2 364.8h-44.8V128c0-17.067-14.933-32-32-32H281.6c-17.067 0-32 14.933-32 32v236.8h-44.8C145.067 364.8 96 413.867 96 473.6v192c0 59.733 49.067 108.8 108.8 108.8h44.8V896c0 17.067 14.933 32 32 32h460.8c17.067 0 32-14.933 32-32V774.4h44.8c59.733 0 108.8-49.067 108.8-108.8v-192c0-59.733-49.067-108.8-108.8-108.8zM313.6 160h396.8v204.8H313.6V160zm396.8 704H313.6V620.8h396.8V864zM864 665.6c0 25.6-19.2 44.8-44.8 44.8h-44.8V588.8c0-17.067-14.933-32-32-32H281.6c-17.067 0-32 14.933-32 32v121.6h-44.8c-25.6 0-44.8-19.2-44.8-44.8v-192c0-25.6 19.2-44.8 44.8-44.8h614.4c25.6 0 44.8 19.2 44.8 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--><h1 id="死区处理" tabindex="-1"><a class="header-anchor" href="#死区处理" aria-hidden="true">#</a> 死区处理</h1><h2 id="旋转门压缩" tabindex="-1"><a class="header-anchor" href="#旋转门压缩" aria-hidden="true">#</a> 旋转门压缩</h2><p>旋转门压缩（SDT）算法是一种死区处理算法。SDT 的计算复杂度较低，并使用线性趋势来表示大量数据。</p><p>在 IoTDB 中，SDT 在刷新到磁盘时会压缩并丢弃数据。</p><p>IoTDB 允许您在创建时间序列时指定 SDT 的属性，并支持以下三个属性：</p><ul><li>CompDev （Compression Deviation，压缩偏差）</li></ul><p>CompDev 是 SDT 中最重要的参数，它表示当前样本与当前线性趋势之间的最大差值。CompDev 设置的值需要大于 0。</p><ul><li>CompMinTime （Compression Minimum Time Interval，最小压缩时间间隔）</li></ul><p>CompMinTime 是测量两个存储的数据点之间的时间距离的参数，用于减少噪声。<br> 如果当前点和最后存储的点之间的时间间隔小于或等于其值，则无论压缩偏差如何，都不会存储当前点。<br> 默认值为 0，单位为毫秒。</p><ul><li>CompMaxTime （Compression Maximum Time Interval，最大压缩时间间隔）</li></ul><p>CompMaxTime 是测量两个存储的数据点之间的时间距离的参数。<br> 如果当前点和最后一个存储点之间的时间间隔大于或等于其值，<br> 无论压缩偏差如何，都将存储当前点。<br> 默认值为 9,223,372,036,854,775,807，单位为毫秒。</p><p>支持的数据类型：</p><ul><li>INT32（整型）</li><li>INT64（长整型）</li><li>FLOAT（单精度浮点数）</li><li>DOUBLE（双精度浮点数）</li></ul><p>SDT 的指定语法详见本文 <a href="/zh/UserGuide/Master/Reference/SQL-Reference.html" class="">SQL 参考文档</a>。</p><p>以下是使用 SDT 压缩的示例。</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>IoTDB&gt; CREATE TIMESERIES root.sg1.d0.s0 WITH DATATYPE=INT32,ENCODING=PLAIN,DEADBAND=SDT,COMPDEV=2
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>刷入磁盘和 SDT 压缩之前，结果如下所示：</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>IoTDB&gt; SELECT s0 FROM root.sg1.d0
+-----------------------------+--------------+
|                         Time|root.sg1.d0.s0|
+-----------------------------+--------------+
|2017-11-01T00:06:00.001+08:00|             1|
|2017-11-01T00:06:00.002+08:00|             1|
|2017-11-01T00:06:00.003+08:00|             1|
|2017-11-01T00:06:00.004+08:00|             1|
|2017-11-01T00:06:00.005+08:00|             1|
|2017-11-01T00:06:00.006+08:00|             1|
|2017-11-01T00:06:00.007+08:00|             1|
|2017-11-01T00:06:00.015+08:00|            10|
|2017-11-01T00:06:00.016+08:00|            20|
|2017-11-01T00:06:00.017+08:00|             1|
|2017-11-01T00:06:00.018+08:00|            30|
+-----------------------------+--------------+
Total line number = 11
It costs 0.008s
</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 class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>刷入磁盘和 SDT 压缩之后，结果如下所示：</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>IoTDB&gt; FLUSH
IoTDB&gt; SELECT s0 FROM root.sg1.d0
+-----------------------------+--------------+
|                         Time|root.sg1.d0.s0|
+-----------------------------+--------------+
|2017-11-01T00:06:00.001+08:00|             1|
|2017-11-01T00:06:00.007+08:00|             1|
|2017-11-01T00:06:00.015+08:00|            10|
|2017-11-01T00:06:00.016+08:00|            20|
|2017-11-01T00:06:00.017+08:00|             1|
+-----------------------------+--------------+
Total line number = 5
It costs 0.044s
</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 class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>SDT 在刷新到磁盘时进行压缩。 SDT 算法始终存储第一个点，并且不存储最后一个点。</p><p>时间范围在 [2017-11-01T00:06:00.001, 2017-11-01T00:06:00.007] 的数据在压缩偏差内，因此被压缩和丢弃。<br> 之所以存储时间为 2017-11-01T00:06:00.007 的数据点，是因为下一个数据点 2017-11-01T00:06:00.015 的值超过压缩偏差。<br> 当一个数据点超过压缩偏差时，SDT 将存储上一个读取的数据点，并重新计算上下压缩边界。作为最后一个数据点，不存储时间 2017-11-01T00:06:00.018。</p></div><!--[--><!----><!--]--><footer class="page-meta"><div class="meta-item edit-link"><a href="https://github.com/apache/iotdb-docs/edit/main/src/zh/UserGuide/Master/stage/Deadband-Process.md" rel="noopener noreferrer" target="_blank" aria-label="发现错误？在 GitHub 上编辑此页" class="nav-link label"><!--[--><svg xmlns="http://www.w3.org/2000/svg" class="icon edit-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="edit icon"><path d="M430.818 653.65a60.46 60.46 0 0 1-50.96-93.281l71.69-114.012 7.773-10.365L816.038 80.138A60.46 60.46 0 0 1 859.225 62a60.46 60.46 0 0 1 43.186 18.138l43.186 43.186a60.46 60.46 0 0 1 0 86.373L588.879 565.55l-8.637 8.637-117.466 68.234a60.46 60.46 0 0 1-31.958 11.229z"></path><path d="M728.802 962H252.891A190.883 190.883 0 0 1 62.008 771.98V296.934a190.883 190.883 0 0 1 190.883-192.61h267.754a60.46 60.46 0 0 1 0 120.92H252.891a69.962 69.962 0 0 0-69.098 69.099V771.98a69.962 69.962 0 0 0 69.098 69.098h475.911A69.962 69.962 0 0 0 797.9 771.98V503.363a60.46 60.46 0 1 1 120.922 0V771.98A190.883 190.883 0 0 1 728.802 962z"></path></svg><!--]-->发现错误？在 GitHub 上编辑此页<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span><!----></a></div><div class="meta-item git-info"><div class="update-time"><span class="label">上次编辑于: </span><!----></div><div class="contributors"><span class="label">贡献者: </span><!--[--><!--[--><span class="contributor" title="email: hhaonan@outlook.com">Haonan</span><!--]--><!--]--></div></div></footer><!----><!----><!--[--><!----><!--]--><!--]--></main><!--]--><footer style="padding-bottom:2rem;"><span id="doc-version" style="display:none;">latest</span><p style="text-align:center;color:#909399;font-size:12px;margin:0 30px;">Copyright © 2024 The Apache Software Foundation.<br> Apache and the Apache feather logo are trademarks of The Apache Software Foundation</p><p style="text-align:center;margin-top:10px;color:#909399;font-size:12px;margin:0 30px;"><strong>Have a question?</strong> Connect with us on QQ, WeChat, or Slack. <a href="https://github.com/apache/iotdb/issues/1995">Join the community</a> now.</p></footer></div><!--]--><!--]--><!----><!--]--></div>
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