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class="vp-page-title"><h1><!---->Deadband Process</h1><div class="page-info"><!----><!----><span class="page-date-info" aria-label="Writing Date"><svg xmlns="http://www.w3.org/2000/svg" class="icon calendar-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="calendar icon"><path d="M716.4 110.137c0-18.753-14.72-33.473-33.472-33.473-18.753 0-33.473 14.72-33.473 33.473v33.473h66.993v-33.473zm-334.87 0c0-18.753-14.72-33.473-33.473-33.473s-33.52 14.72-33.52 33.473v33.473h66.993v-33.473zm468.81 33.52H716.4v100.465c0 18.753-14.72 33.473-33.472 33.473a33.145 33.145 0 01-33.473-33.473V143.657H381.53v100.465c0 18.753-14.72 33.473-33.473 33.473a33.145 33.145 0 01-33.473-33.473V143.657H180.6A134.314 134.314 0 0046.66 277.595v535.756A134.314 134.314 0 00180.6 947.289h669.74a134.36 134.36 0 00133.94-133.938V277.595a134.314 134.314 0 00-133.94-133.938zm33.473 267.877H147.126a33.145 33.145 0 01-33.473-33.473c0-18.752 14.72-33.473 33.473-33.473h736.687c18.752 0 33.472 14.72 33.472 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tabindex="-1"><a class="header-anchor" href="#sdt"><span>SDT</span></a></h2><p>The Swinging Door Trending (SDT) algorithm is a deadband process algorithm.<br> SDT has low computational complexity and uses a linear trend to represent a quantity of data.</p><p>In IoTDB SDT compresses and discards data when flushing into the disk.</p><p>IoTDB allows you to specify the properties of SDT when creating a time series, and supports three properties:</p><ul><li>CompDev (Compression Deviation)</li></ul><p>CompDev is the most important parameter in SDT that represents the maximum difference between the<br> current sample and the current linear trend. CompDev needs to be greater than 0 to perform compression.</p><ul><li>CompMinTime (Compression Minimum Time Interval)</li></ul><p>CompMinTime is a parameter measures the time distance between two stored data points, which is used for noisy reduction.<br> If the time interval between the current point and the last stored point is less than or equal to its value,<br> current point will NOT be stored regardless of compression deviation.<br> The default value is 0 with time unit ms.</p><ul><li>CompMaxTime (Compression Maximum Time Interval)</li></ul><p>CompMaxTime is a parameter measure the time distance between two stored data points.<br> If the time interval between the current point and the last stored point is greater than or equal to its value,<br> current point will be stored regardless of compression deviation.<br> The default value is 9,223,372,036,854,775,807 with time unit ms.</p><p>The specified syntax for SDT is detailed in <a class="route-link" href="/UserGuide/V0.13.x/Reference/SQL-Reference.html">Create Timeseries Statement</a>.</p><p>Supported datatypes:</p><ul><li>INT32 (Integer)</li><li>INT64 (Long Integer)</li><li>FLOAT (Single Precision Floating Point)</li><li>DOUBLE (Double Precision Floating Point)</li></ul><p>The following is an example of using SDT compression.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; CREATE TIMESERIES root.sg1.d0.s0 WITH DATATYPE=INT32,ENCODING=PLAIN,LOSS=SDT,COMPDEV=2
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Prior to flushing and SDT compression, the results are shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="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>After flushing and SDT compression, the results are shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="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 takes effect when flushing to the disk. The SDT algorithm always stores the first point and does not store the last point.</p><p>The data in [2017-11-01T00:06:00.001, 2017-11-01T00:06:00.007] is within the compression deviation thus discarded.<br> The data point at time 2017-11-01T00:06:00.007 is stored because the next data point at time 2017-11-01T00:06:00.015<br> exceeds compression deviation. When a data point exceeds the compression deviation, SDT stores the last read<br> point and updates the upper and lower boundaries. The last point at time 2017-11-01T00:06:00.018 is not stored.</p></div><!--[--><!----><!--]--><footer class="vp-page-meta"><div class="vp-meta-item edit-link"><a href="https://github.com/apache/iotdb-docs/edit/main/src/UserGuide/V0.13.x/Data-Concept/Deadband-Process.md" rel="noopener noreferrer" target="_blank" aria-label="Found Error? Edit this page on GitHub" class="nav-link vp-meta-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><!--]-->Found Error? Edit this page on GitHub<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="vp-meta-item git-info"><div class="update-time"><span class="vp-meta-label">Last update: </span><!----></div><!----></div></footer><nav class="vp-page-nav"><a class="route-link nav-link prev" href="/UserGuide/V0.13.x/Data-Concept/Data-Type.html" aria-label="Data Type"><div class="hint"><span class="arrow start"></span>Prev</div><div class="link"><!---->Data Type</div></a><a class="route-link nav-link next" href="/UserGuide/V0.13.x/Data-Concept/Encoding.html" aria-label="Encoding"><div class="hint">Next<span class="arrow end"></span></div><div class="link">Encoding<!----></div></a></nav><!----><!--[--><!----><!--]--><!--]--></main><!--]--><footer style="padding-bottom:2rem;"><span id="doc-version" style="display:none;">rel/0.13</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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