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--><h1 id="compression" tabindex="-1"><a class="header-anchor" href="#compression" aria-hidden="true">#</a> Compression</h1><p>When the time series is written and encoded as binary data according to the specified type, IoTDB compresses the data using compression technology to further improve space storage efficiency. Although both encoding and compression are designed to improve storage efficiency, encoding techniques are usually available only for specific data types (e.g., second-order differential encoding is only suitable for INT32 or INT64 data type, and storing floating-point numbers requires multiplying them by 10m to convert to integers), after which the data is converted to a binary stream. The compression method (SNAPPY) compresses the binary stream, so the use of the compression method is no longer limited by the data type.</p><h2 id="basic-compression-methods" tabindex="-1"><a class="header-anchor" href="#basic-compression-methods" aria-hidden="true">#</a> Basic Compression Methods</h2><p>IoTDB allows you to specify the compression method of the column when creating a time series, and supports the following compression methods:</p><ul><li><p>UNCOMPRESSED</p></li><li><p>SNAPPY</p></li><li><p>LZ4</p></li><li><p>GZIP</p></li></ul><p>The specified syntax for compression is detailed in <a href="/UserGuide/V1.0.x/Reference/SQL-Reference.html" class="">Create Timeseries Statement</a>.</p><h2 id="compression-ratio-statistics" tabindex="-1"><a class="header-anchor" href="#compression-ratio-statistics" aria-hidden="true">#</a> Compression Ratio Statistics</h2><p memtable_flush_time="">Compression ratio statistics file: data/system/compression_ratio/Ratio-{ratio_sum}-</p><ul><li>ratio_sum: sum of memtable compression ratios</li><li>memtable_flush_time: memtable flush times</li></ul><p>The average compression ratio can be calculated by <code>ratio_sum / memtable_flush_time</code></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/Compression.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/Encoding.html" class="nav-link prev" aria-label="Encoding"><div class="hint"><span class="arrow start"></span>Prev</div><div class="link"><!---->Encoding</div></a><a href="/UserGuide/V1.0.x/Data-Concept/Time-Partition.html" class="nav-link next" aria-label="Time Partition of Data"><div class="hint">Next<span class="arrow end"></span></div><div class="link">Time Partition of Data<!----></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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