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class="page-info"><!----><!----><!----><!----><span class="page-reading-time-info" aria-label="Reading Time"><svg xmlns="http://www.w3.org/2000/svg" class="icon timer-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="timer icon"><path d="M799.387 122.15c4.402-2.978 7.38-7.897 7.38-13.463v-1.165c0-8.933-7.38-16.312-16.312-16.312H256.33c-8.933 0-16.311 7.38-16.311 16.312v1.165c0 5.825 2.977 10.874 7.637 13.592 4.143 194.44 97.22 354.963 220.201 392.763-122.204 37.542-214.893 196.511-220.2 389.397-4.661 5.049-7.638 11.651-7.638 19.03v5.825h566.49v-5.825c0-7.379-2.849-13.981-7.509-18.9-5.049-193.016-97.867-351.985-220.2-389.527 123.24-37.67 216.446-198.453 220.588-392.892zM531.16 450.445v352.632c117.674 1.553 211.787 40.778 211.787 88.676H304.097c0-48.286 95.149-87.382 213.728-88.676V450.445c-93.077-3.107-167.901-81.297-167.901-177.093 0-8.803 6.99-15.793 15.793-15.793 8.803 0 15.794 6.99 15.794 15.793 0 80.261 63.69 145.635 142.01 145.635s142.011-65.374 142.011-145.635c0-8.803 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--><h1 id="deadband-process" tabindex="-1"><a class="header-anchor" href="#deadband-process" aria-hidden="true">#</a> Deadband Process</h1><h2 id="sdt" tabindex="-1"><a class="header-anchor" href="#sdt" aria-hidden="true">#</a> SDT</h2><p>The Swinging Door Trending (SDT) algorithm is a deadband process algorithm. 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 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. If the time interval between the current point and the last stored point is less than or equal to its value, current point will NOT be stored regardless of compression deviation. 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. If the time interval between the current point and the last stored point is greater than or equal to its value, current point will be stored regardless of compression deviation. 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 href="/UserGuide/V1.0.x/Reference/SQL-Reference.html" class="">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"><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>Prior to flushing and SDT compression, the results are shown below:</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>After flushing and SDT compression, the results are shown below:</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 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. 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 exceeds compression deviation. When a data point exceeds the compression deviation, SDT stores the last read 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="page-meta"><div class="meta-item edit-link"><a href="https://github.com/apache/iotdb/edit/rel/1.0/docs/UserGuide/Data-Concept/Deadband-Process.md" rel="noopener noreferrer" target="_blank" aria-label="Found Error? Edit this page on GitHub" 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><!--]-->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="meta-item git-info"><!----><!----></div></footer><nav class="page-nav"><a href="/UserGuide/V1.0.x/Data-Concept/Data-Type.html" class="nav-link prev" aria-label="Data Type"><div class="hint"><span class="arrow start"></span>Prev</div><div class="link"><!---->Data Type</div></a><a href="/UserGuide/V1.0.x/Data-Concept/Encoding.html" class="nav-link next" 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/1.0</span><p style="text-align:center;color:#909399;font-size:12px;margin:0 30px;">Copyright © 2023 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><p style="text-align:center;margin-top:10px;color:#909399;font-size:12px;margin:0 30px;"> We use <a href="https://analytics.google.com">Google Analytics</a> to collect anonymous, aggregated usage information. </p></footer></div><!--]--><!--]--><!----><!--]--></div>
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