<!doctype html>
<html lang="en-US" data-theme="light">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width,initial-scale=1" />
    <meta name="generator" content="VuePress 2.0.0-rc.9" />
    <meta name="theme" content="VuePress Theme Hope 2.0.0-rc.34" />
    <style>
      html {
        background: var(--bg-color, #fff);
      }

      html[data-theme="dark"] {
        background: var(--bg-color, #1d1e1f);
      }

      body {
        background: var(--bg-color);
      }
    </style>
    <script>
      const userMode = localStorage.getItem("vuepress-theme-hope-scheme");
      const systemDarkMode =
        window.matchMedia &&
        window.matchMedia("(prefers-color-scheme: dark)").matches;

      if (userMode === "dark" || (userMode !== "light" && systemDarkMode)) {
        document.documentElement.setAttribute("data-theme", "dark");
      }
    </script>
    <link rel="alternate" hreflang="zh-cn" href="https://iotdb.apache.org/zh/UserGuide/V1.0.x/Operators-Functions/Sample.html"><meta property="og:url" content="https://iotdb.apache.org/UserGuide/V1.0.x/Operators-Functions/Sample.html"><meta property="og:site_name" content="IoTDB Website"><meta property="og:title" content="Sample Functions"><meta property="og:description" content="Sample Functions Equal Size Bucket Sample Function Equal Size Bucket Random Sample Function This function samples the input sequence in equal size buckets, that is, according to..."><meta property="og:type" content="article"><meta property="og:locale" content="en-US"><meta property="og:locale:alternate" content="zh-CN"><meta property="og:updated_time" content="2023-07-10T03:11:17.000Z"><meta property="article:modified_time" content="2023-07-10T03:11:17.000Z"><script type="application/ld+json">{"@context":"https://schema.org","@type":"Article","headline":"Sample Functions","image":[""],"dateModified":"2023-07-10T03:11:17.000Z","author":[]}</script><link rel="icon" href="/favicon.ico"><meta name="Description" content="Apache IoTDB: Time Series Database for IoT"><meta name="Keywords" content="TSDB, time series, time series database, IoTDB, IoT database, IoT data management,时序数据库, 时间序列管理, IoTDB, 物联网数据库, 实时数据库, 物联网数据管理, 物联网数据"><meta name="baidu-site-verification" content="wfKETzB3OT"><meta name="google-site-verification" content="mZWAoRY0yj_HAr-s47zHCGHzx5Ju-RVm5wDbPnwQYFo"><script type="text/javascript">
var _paq = window._paq = window._paq || [];
/* tracker methods like "setCustomDimension" should be called before "trackPageView" */
_paq.push(["setDoNotTrack", true]);
_paq.push(["disableCookies"]);
_paq.push(['trackPageView']);
_paq.push(['enableLinkTracking']);
(function() {
  var u="https://analytics.apache.org/";
  _paq.push(['setTrackerUrl', u+'matomo.php']);
  _paq.push(['setSiteId', '56']);
  var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0];
  g.async=true; g.src=u+'matomo.js'; s.parentNode.insertBefore(g,s);
})();
       </script><title>Sample Functions | IoTDB Website</title><meta name="description" content="Sample Functions Equal Size Bucket Sample Function Equal Size Bucket Random Sample Function This function samples the input sequence in equal size buckets, that is, according to...">
    <link rel="preload" href="/assets/style-DnEHAOmf.css" as="style"><link rel="stylesheet" href="/assets/style-DnEHAOmf.css">
    <link rel="modulepreload" href="/assets/app-B-0YFdX2.js"><link rel="modulepreload" href="/assets/Sample.html-C48p3Vl9.js">
    
  </head>
  <body>
    <div id="app"><!--[--><!--[--><!--[--><span tabindex="-1"></span><a href="#main-content" class="vp-skip-link sr-only">Skip to main content</a><!--]--><!--[--><div class="theme-container has-toc"><!--[--><header id="navbar" class="vp-navbar hide-icon"><div class="vp-navbar-start"><button type="button" class="vp-toggle-sidebar-button" title="Toggle Sidebar"><span class="icon"></span></button><!--[--><!----><!--]--><!--[--><a class="route-link vp-brand" href="/"><img class="vp-nav-logo" src="/logo.png" alt><!----><span class="vp-site-name hide-in-pad">IoTDB Website</span></a><!--]--><!--[--><!----><!--]--></div><div class="vp-navbar-center"><!--[--><!----><!--]--><!--[--><!--]--><!--[--><!----><!--]--></div><div class="vp-navbar-end"><!--[--><!----><!--]--><!--[--><!--[--><div id="docsearch-container" style="display:none;"></div><div><button type="button" class="DocSearch DocSearch-Button" aria-label="Search"><span class="DocSearch-Button-Container"><svg width="20" height="20" class="DocSearch-Search-Icon" viewBox="0 0 20 20"><path d="M14.386 14.386l4.0877 4.0877-4.0877-4.0877c-2.9418 2.9419-7.7115 2.9419-10.6533 0-2.9419-2.9418-2.9419-7.7115 0-10.6533 2.9418-2.9419 7.7115-2.9419 10.6533 0 2.9419 2.9418 2.9419 7.7115 0 10.6533z" stroke="currentColor" fill="none" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round"></path></svg><span class="DocSearch-Button-Placeholder">Search</span></span><span class="DocSearch-Button-Keys"><kbd class="DocSearch-Button-Key"><svg width="15" height="15" class="DocSearch-Control-Key-Icon"><path d="M4.505 4.496h2M5.505 5.496v5M8.216 4.496l.055 5.993M10 7.5c.333.333.5.667.5 1v2M12.326 4.5v5.996M8.384 4.496c1.674 0 2.116 0 2.116 1.5s-.442 1.5-2.116 1.5M3.205 9.303c-.09.448-.277 1.21-1.241 1.203C1 10.5.5 9.513.5 8V7c0-1.57.5-2.5 1.464-2.494.964.006 1.134.598 1.24 1.342M12.553 10.5h1.953" stroke-width="1.2" stroke="currentColor" fill="none" stroke-linecap="square"></path></svg></kbd><kbd class="DocSearch-Button-Key">K</kbd></span></button></div><!--]--><nav class="vp-nav-links"><div class="vp-nav-item hide-in-mobile"><div class="dropdown-wrapper"><button type="button" class="dropdown-title" aria-label="Documentation"><span class="title"><!---->Documentation</span><span class="arrow"></span><ul class="nav-dropdown"><li class="dropdown-item"><a class="route-link nav-link" href="/UserGuide/latest/QuickStart/QuickStart.html" aria-label="v1.3.x"><!---->v1.3.x<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/UserGuide/V1.2.x/QuickStart/QuickStart.html" aria-label="v1.2.x"><!---->v1.2.x<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/UserGuide/V1.1.x/QuickStart/QuickStart.html" aria-label="v1.1.x"><!---->v1.1.x<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/UserGuide/V1.0.x/QuickStart/QuickStart.html" aria-label="v1.0.x"><!---->v1.0.x<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/UserGuide/V0.13.x/QuickStart/QuickStart.html" aria-label="v0.13.x"><!---->v0.13.x<!----></a></li></ul></button></div></div><div class="vp-nav-item hide-in-mobile"><a href="https://cwiki.apache.org/confluence/display/IOTDB/System+Design" rel="noopener noreferrer" target="_blank" aria-label="Design" class="nav-link"><!---->Design<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-nav-item hide-in-mobile"><a class="route-link nav-link" href="/Download/" aria-label="Download"><!---->Download<!----></a></div><div class="vp-nav-item hide-in-mobile"><div class="dropdown-wrapper"><button type="button" class="dropdown-title" aria-label="Community"><span class="title"><!---->Community</span><span class="arrow"></span><ul class="nav-dropdown"><li class="dropdown-item"><a class="route-link nav-link" href="/Community/About.html" aria-label="About"><!---->About<!----></a></li><li class="dropdown-item"><a href="https://cwiki.apache.org/confluence/display/iotdb" rel="noopener noreferrer" target="_blank" aria-label="Wiki" class="nav-link"><!---->Wiki<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></li><li class="dropdown-item"><a class="route-link nav-link" href="/Community/Community-Project-Committers.html" aria-label="People"><!---->People<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/Community/Community-Powered-By.html" aria-label="Powered  By"><!---->Powered  By<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/Community/Materials.html" aria-label="Resources"><!---->Resources<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/Community/Feedback.html" aria-label="Feedback"><!---->Feedback<!----></a></li></ul></button></div></div><div class="vp-nav-item hide-in-mobile"><div class="dropdown-wrapper"><button type="button" class="dropdown-title" aria-label="Development"><span class="title"><!---->Development</span><span class="arrow"></span><ul class="nav-dropdown"><li class="dropdown-item"><a class="route-link nav-link" href="/Development/VoteRelease.html" aria-label="How  to  vote"><!---->How  to  vote<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/Development/HowToCommit.html" aria-label="How  to  Commit"><!---->How  to  Commit<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/Development/HowToJoin.html" aria-label="Become  a  Contributor"><!---->Become  a  Contributor<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/Development/Committer.html" aria-label="Become  a  Committer"><!---->Become  a  Committer<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/Development/ContributeGuide.html" aria-label="ContributeGuide"><!---->ContributeGuide<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/Development/HowtoContributeCode.html" aria-label="How  to  Contribute  Code"><!---->How  to  Contribute  Code<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/Development/format-changelist.html" aria-label="Changelist  of  TsFile"><!---->Changelist  of  TsFile<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/Development/rpc-changelist.html" aria-label="Changelist  of  RPC"><!---->Changelist  of  RPC<!----></a></li></ul></button></div></div><div class="vp-nav-item hide-in-mobile"><div class="dropdown-wrapper"><button type="button" class="dropdown-title" aria-label="ASF"><span class="title"><!---->ASF</span><span class="arrow"></span><ul class="nav-dropdown"><li class="dropdown-item"><a href="https://www.apache.org/" rel="noopener noreferrer" target="_blank" aria-label="Foundation" class="nav-link"><!---->Foundation<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></li><li class="dropdown-item"><a href="https://www.apache.org/licenses/" rel="noopener noreferrer" target="_blank" aria-label="License" class="nav-link"><!---->License<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></li><li class="dropdown-item"><a href="https://www.apache.org/security/" rel="noopener noreferrer" target="_blank" aria-label="Security" class="nav-link"><!---->Security<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></li><li class="dropdown-item"><a href="https://www.apache.org/foundation/sponsorship.html" rel="noopener noreferrer" target="_blank" aria-label="Sponsorship" class="nav-link"><!---->Sponsorship<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></li><li class="dropdown-item"><a href="https://www.apache.org/foundation/thanks.html" rel="noopener noreferrer" target="_blank" aria-label="Thanks" class="nav-link"><!---->Thanks<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></li><li class="dropdown-item"><a href="https://www.apache.org/events/current-event" rel="noopener noreferrer" target="_blank" aria-label="Current  Events" class="nav-link"><!---->Current  Events<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></li><li class="dropdown-item"><a href="https://privacy.apache.org/policies/privacy-policy-public.html" rel="noopener noreferrer" target="_blank" aria-label="Privacy" class="nav-link"><!---->Privacy<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></li></ul></button></div></div></nav><div class="vp-nav-item"><div class="dropdown-wrapper"><button type="button" class="dropdown-title" aria-label="Select language"><!--[--><svg xmlns="http://www.w3.org/2000/svg" class="icon i18n-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="i18n icon" style="width:1rem;height:1rem;vertical-align:middle;"><path d="M379.392 460.8 494.08 575.488l-42.496 102.4L307.2 532.48 138.24 701.44l-71.68-72.704L234.496 460.8l-45.056-45.056c-27.136-27.136-51.2-66.56-66.56-108.544h112.64c7.68 14.336 16.896 27.136 26.112 35.84l45.568 46.08 45.056-45.056C382.976 312.32 409.6 247.808 409.6 204.8H0V102.4h256V0h102.4v102.4h256v102.4H512c0 70.144-37.888 161.28-87.04 210.944L378.88 460.8zM576 870.4 512 1024H409.6l256-614.4H768l256 614.4H921.6l-64-153.6H576zM618.496 768h196.608L716.8 532.48 618.496 768z"></path></svg><!--]--><span class="arrow"></span><ul class="nav-dropdown"><li class="dropdown-item"><a class="route-link nav-link active" href="/UserGuide/V1.0.x/Operators-Functions/Sample.html" aria-label="English"><!---->English<!----></a></li><li class="dropdown-item"><a class="route-link nav-link" href="/zh/UserGuide/V1.0.x/Operators-Functions/Sample.html" aria-label="简体中文"><!---->简体中文<!----></a></li></ul></button></div></div><div class="vp-nav-item hide-in-mobile"><button type="button" id="appearance-switch"><svg xmlns="http://www.w3.org/2000/svg" class="icon auto-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="auto icon" style="display:none;"><path d="M512 992C246.92 992 32 777.08 32 512S246.92 32 512 32s480 214.92 480 480-214.92 480-480 480zm0-840c-198.78 0-360 161.22-360 360 0 198.84 161.22 360 360 360s360-161.16 360-360c0-198.78-161.22-360-360-360zm0 660V212c165.72 0 300 134.34 300 300 0 165.72-134.28 300-300 300z"></path></svg><svg xmlns="http://www.w3.org/2000/svg" class="icon dark-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="dark icon" style="display:none;"><path d="M524.8 938.667h-4.267a439.893 439.893 0 0 1-313.173-134.4 446.293 446.293 0 0 1-11.093-597.334A432.213 432.213 0 0 1 366.933 90.027a42.667 42.667 0 0 1 45.227 9.386 42.667 42.667 0 0 1 10.24 42.667 358.4 358.4 0 0 0 82.773 375.893 361.387 361.387 0 0 0 376.747 82.774 42.667 42.667 0 0 1 54.187 55.04 433.493 433.493 0 0 1-99.84 154.88 438.613 438.613 0 0 1-311.467 128z"></path></svg><svg xmlns="http://www.w3.org/2000/svg" class="icon light-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="light icon" style="display:block;"><path d="M952 552h-80a40 40 0 0 1 0-80h80a40 40 0 0 1 0 80zM801.88 280.08a41 41 0 0 1-57.96-57.96l57.96-58a41.04 41.04 0 0 1 58 58l-58 57.96zM512 752a240 240 0 1 1 0-480 240 240 0 0 1 0 480zm0-560a40 40 0 0 1-40-40V72a40 40 0 0 1 80 0v80a40 40 0 0 1-40 40zm-289.88 88.08-58-57.96a41.04 41.04 0 0 1 58-58l57.96 58a41 41 0 0 1-57.96 57.96zM192 512a40 40 0 0 1-40 40H72a40 40 0 0 1 0-80h80a40 40 0 0 1 40 40zm30.12 231.92a41 41 0 0 1 57.96 57.96l-57.96 58a41.04 41.04 0 0 1-58-58l58-57.96zM512 832a40 40 0 0 1 40 40v80a40 40 0 0 1-80 0v-80a40 40 0 0 1 40-40zm289.88-88.08 58 57.96a41.04 41.04 0 0 1-58 58l-57.96-58a41 41 0 0 1 57.96-57.96z"></path></svg></button></div><div class="vp-nav-item vp-action"><a class="vp-action-link" href="https://github.com/apache/iotdb" target="_blank" rel="noopener noreferrer" aria-label="GitHub"><svg xmlns="http://www.w3.org/2000/svg" class="icon github-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="github icon" style="width:1.25rem;height:1.25rem;vertical-align:middle;"><path d="M511.957 21.333C241.024 21.333 21.333 240.981 21.333 512c0 216.832 140.544 400.725 335.574 465.664 24.49 4.395 32.256-10.07 32.256-23.083 0-11.69.256-44.245 0-85.205-136.448 29.61-164.736-64.64-164.736-64.64-22.315-56.704-54.4-71.765-54.4-71.765-44.587-30.464 3.285-29.824 3.285-29.824 49.195 3.413 75.179 50.517 75.179 50.517 43.776 75.008 114.816 53.333 142.762 40.79 4.523-31.66 17.152-53.377 31.19-65.537-108.971-12.458-223.488-54.485-223.488-242.602 0-53.547 19.114-97.323 50.517-131.67-5.035-12.33-21.93-62.293 4.779-129.834 0 0 41.258-13.184 134.912 50.346a469.803 469.803 0 0 1 122.88-16.554c41.642.213 83.626 5.632 122.88 16.554 93.653-63.488 134.784-50.346 134.784-50.346 26.752 67.541 9.898 117.504 4.864 129.834 31.402 34.347 50.474 78.123 50.474 131.67 0 188.586-114.73 230.016-224.042 242.09 17.578 15.232 33.578 44.672 33.578 90.454v135.85c0 13.142 7.936 27.606 32.854 22.87C862.25 912.597 1002.667 728.747 1002.667 512c0-271.019-219.648-490.667-490.71-490.667z"></path></svg></a></div><!--]--><!--[--><!----><!--]--><button type="button" class="vp-toggle-navbar-button" aria-label="Toggle Navbar" aria-expanded="false" aria-controls="nav-screen"><span><span class="vp-top"></span><span class="vp-middle"></span><span class="vp-bottom"></span></span></button></div></header><!----><!--]--><!----><div class="toggle-sidebar-wrapper"><span class="arrow start"></span></div><aside id="sidebar" class="vp-sidebar"><!--[--><!----><!--]--><ul class="vp-sidebar-links"><li><section class="vp-sidebar-group"><p class="vp-sidebar-header"><!----><span class="vp-sidebar-title">IoTDB User Guide (V1.0.x)</span><!----></p><ul class="vp-sidebar-links"></ul></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">About IoTDB</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Quick Start</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Data Concept</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Syntax Conventions</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">API</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Operate Metadata</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Write Data (Update Data)</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Delete Data</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Query Data</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable active" type="button"><!----><span class="vp-sidebar-title">Operators and Functions</span><span class="vp-arrow down"></span></button><ul class="vp-sidebar-links"><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Overview.html" aria-label="Overview"><!---->Overview<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/User-Defined-Function.html" aria-label="UDF (User Defined Function)"><!---->UDF (User Defined Function)<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Aggregation.html" aria-label="Aggregation"><!---->Aggregation<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Mathematical.html" aria-label="Mathematical"><!---->Mathematical<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Comparison.html" aria-label="Comparison"><!---->Comparison<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Logical.html" aria-label="Logical"><!---->Logical<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Conversion.html" aria-label="Conversion"><!---->Conversion<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Constant.html" aria-label="Constant"><!---->Constant<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Selection.html" aria-label="Selection"><!---->Selection<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Continuous-Interval.html" aria-label="Continuous Interval"><!---->Continuous Interval<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Variation-Trend.html" aria-label="Variation Trend"><!---->Variation Trend<!----></a></li><li><a class="route-link nav-link active vp-sidebar-link vp-sidebar-page active" href="/UserGuide/V1.0.x/Operators-Functions/Sample.html" aria-label="Sample"><!---->Sample<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Time-Series.html" aria-label="Time-Series"><!---->Time-Series<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Lambda.html" aria-label="Lambda"><!---->Lambda<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Data-Profiling.html" aria-label="Data Profiling"><!---->Data Profiling<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Anomaly-Detection.html" aria-label="Anomaly Detection"><!---->Anomaly Detection<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Data-Matching.html" aria-label="Data Matching"><!---->Data Matching<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Frequency-Domain.html" aria-label="Frequency Domain"><!---->Frequency Domain<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Data-Quality.html" aria-label="Data Quality"><!---->Data Quality<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Data-Repairing.html" aria-label="Data Repairing"><!---->Data Repairing<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Operators-Functions/Series-Discovery.html" aria-label="Series Discovery"><!---->Series Discovery<!----></a></li></ul></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Trigger</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Monitor and Alert</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Administration Management</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Maintenance Tools</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Collaboration of Edge and Cloud</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Ecosystem Integration</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Cluster</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">FAQ</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-header clickable" type="button"><!----><span class="vp-sidebar-title">Reference</span><span class="vp-arrow end"></span></button><!----></section></li></ul><!--[--><!----><!--]--></aside><!--[--><main id="main-content" class="vp-page"><!--[--><!--[--><!----><!--]--><!----><nav class="vp-breadcrumb disable"></nav><div class="vp-page-title"><h1><!---->Sample Functions</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 33.473a33.145 33.145 0 01-33.472 33.473z"></path></svg><span><!----></span><meta property="datePublished" content="2023-07-10T03:11:17.000Z"></span><span class="page-pageview-info" aria-label="Page views"><svg xmlns="http://www.w3.org/2000/svg" class="icon eye-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="eye icon"><path d="M992 512.096c0-5.76-.992-10.592-1.28-11.136-.192-2.88-1.152-8.064-2.08-10.816-.256-.672-.544-1.376-.832-2.08-.48-1.568-1.024-3.104-1.6-4.32C897.664 290.112 707.104 160 512 160c-195.072 0-385.632 130.016-473.76 322.592-1.056 2.112-1.792 4.096-2.272 5.856a55.512 55.512 0 00-.64 1.6c-1.76 5.088-1.792 8.64-1.632 7.744-.832 3.744-1.568 11.168-1.568 11.168-.224 2.272-.224 4.032.032 6.304 0 0 .736 6.464 1.088 7.808.128 1.824.576 4.512 1.12 6.976h-.032c.448 2.08 1.12 4.096 1.984 6.08.48 1.536.992 2.976 1.472 4.032C126.432 733.856 316.992 864 512 864c195.136 0 385.696-130.048 473.216-321.696 1.376-2.496 2.24-4.832 2.848-6.912.256-.608.48-1.184.672-1.728 1.536-4.48 1.856-8.32 1.728-8.32l-.032.032c.608-3.104 1.568-7.744 1.568-13.28zM512 672c-88.224 0-160-71.776-160-160s71.776-160 160-160 160 71.776 160 160-71.776 160-160 160z"></path></svg><span id="ArtalkPV" class="vp-pageview waline-pageview-count" data-path="/UserGuide/V1.0.x/Operators-Functions/Sample.html" data-page-key="/UserGuide/V1.0.x/Operators-Functions/Sample.html">...</span></span><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 6.99-15.793 15.794-15.793s15.793 6.99 15.793 15.793c0 95.019-73.789 172.82-165.96 177.093z"></path></svg><span>About 11 min</span><meta property="timeRequired" content="PT11M"></span><!----><!----></div><hr></div><div class="vp-toc-placeholder"><aside id="toc"><!--[--><!----><!--]--><div class="vp-toc-header">On This Page<button type="button" class="print-button" title="Print"><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 44.8v192z"></path></svg></button><div class="arrow end"></div></div><div class="vp-toc-wrapper"><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#equal-size-bucket-sample-function">Equal Size Bucket Sample Function</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#equal-size-bucket-random-sample-function">Equal Size Bucket Random Sample Function</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#equal-size-bucket-aggregation-sample">Equal Size Bucket Aggregation Sample</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#equal-size-bucket-m4-sample">Equal Size Bucket M4 Sample</a></li><!----><!--]--></ul></li><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#m4-function">M4 Function</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#attributes">Attributes</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#examples">Examples</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#suggested-use-cases">Suggested Use Cases</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#comparison-with-other-sql">Comparison with Other SQL</a></li><!----><!--]--></ul></li><!--]--></ul><div class="vp-toc-marker" style="top:-1.7rem;"></div></div><!--[--><!----><!--]--></aside></div><!--[--><!----><!--]--><div class="theme-hope-content"><h1 id="sample-functions" tabindex="-1"><a class="header-anchor" href="#sample-functions"><span>Sample Functions</span></a></h1><h2 id="equal-size-bucket-sample-function" tabindex="-1"><a class="header-anchor" href="#equal-size-bucket-sample-function"><span>Equal Size Bucket Sample Function</span></a></h2><h3 id="equal-size-bucket-random-sample-function" tabindex="-1"><a class="header-anchor" href="#equal-size-bucket-random-sample-function"><span>Equal Size Bucket Random Sample Function</span></a></h3><p>This function samples the input sequence in equal size buckets, that is, according to the downsampling ratio and downsampling method given by the user, the input sequence is equally divided into several buckets according to a fixed number of points. Sampling by the given sampling method within each bucket.</p><ul><li><code>proportion</code>: sample ratio, the value range is <code>(0, 1]</code>.</li></ul><h4 id="equal-size-bucket-random-sample" tabindex="-1"><a class="header-anchor" href="#equal-size-bucket-random-sample"><span>Equal Size Bucket Random Sample</span></a></h4><p>Random sampling is performed on the equally divided buckets.</p><table><thead><tr><th>Function Name</th><th>Allowed Input Series Data Types</th><th>Required Attributes</th><th>Output Series Data Type</th><th>Series Data Type Description</th></tr></thead><tbody><tr><td>EQUAL_SIZE_BUCKET_RANDOM_SAMPLE</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td><code>proportion</code> The value range is <code>(0, 1]</code>, the default is <code>0.1</code></td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>Returns a random sample of equal buckets that matches the sampling ratio</td></tr></tbody></table><p>Example data: <code>root.ln.wf01.wt01.temperature</code> has a total of <code>100</code> ordered data from <code>0.0-99.0</code>.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; select temperature from root.ln.wf01.wt01;
+-----------------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.temperature|
+-----------------------------+-----------------------------+
|1970-01-01T08:00:00.000+08:00|                          0.0|
|1970-01-01T08:00:00.001+08:00|                          1.0|
|1970-01-01T08:00:00.002+08:00|                          2.0|
|1970-01-01T08:00:00.003+08:00|                          3.0|
|1970-01-01T08:00:00.004+08:00|                          4.0|
|1970-01-01T08:00:00.005+08:00|                          5.0|
|1970-01-01T08:00:00.006+08:00|                          6.0|
|1970-01-01T08:00:00.007+08:00|                          7.0|
|1970-01-01T08:00:00.008+08:00|                          8.0|
|1970-01-01T08:00:00.009+08:00|                          9.0|
|1970-01-01T08:00:00.010+08:00|                         10.0|
|1970-01-01T08:00:00.011+08:00|                         11.0|
|1970-01-01T08:00:00.012+08:00|                         12.0|
|.............................|.............................|            
|1970-01-01T08:00:00.089+08:00|                         89.0|
|1970-01-01T08:00:00.090+08:00|                         90.0|
|1970-01-01T08:00:00.091+08:00|                         91.0|
|1970-01-01T08:00:00.092+08:00|                         92.0|
|1970-01-01T08:00:00.093+08:00|                         93.0|
|1970-01-01T08:00:00.094+08:00|                         94.0|
|1970-01-01T08:00:00.095+08:00|                         95.0|
|1970-01-01T08:00:00.096+08:00|                         96.0|
|1970-01-01T08:00:00.097+08:00|                         97.0|
|1970-01-01T08:00:00.098+08:00|                         98.0|
|1970-01-01T08:00:00.099+08:00|                         99.0|
+-----------------------------+-----------------------------+
</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 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>Sql:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> equal_size_bucket_random_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span><span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> random_sample <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Result:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------+
|                         Time|random_sample|
+-----------------------------+-------------+
|1970-01-01T08:00:00.007+08:00|          7.0|
|1970-01-01T08:00:00.014+08:00|         14.0|
|1970-01-01T08:00:00.020+08:00|         20.0|
|1970-01-01T08:00:00.035+08:00|         35.0|
|1970-01-01T08:00:00.047+08:00|         47.0|
|1970-01-01T08:00:00.059+08:00|         59.0|
|1970-01-01T08:00:00.063+08:00|         63.0|
|1970-01-01T08:00:00.079+08:00|         79.0|
|1970-01-01T08:00:00.086+08:00|         86.0|
|1970-01-01T08:00:00.096+08:00|         96.0|
+-----------------------------+-------------+
Total line number = 10
It costs 0.024s
</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></div><h3 id="equal-size-bucket-aggregation-sample" tabindex="-1"><a class="header-anchor" href="#equal-size-bucket-aggregation-sample"><span>Equal Size Bucket Aggregation Sample</span></a></h3><p>The input sequence is sampled by the aggregation sampling method, and the user needs to provide an additional aggregation function parameter, namely</p><ul><li><code>type</code>: Aggregate type, which can be <code>avg</code> or <code>max</code> or <code>min</code> or <code>sum</code> or <code>extreme</code> or <code>variance</code>. By default, <code>avg</code> is used. <code>extreme</code> represents the value with the largest absolute value in the equal bucket. <code>variance</code> represents the variance in the sampling equal buckets.</li></ul><p>The timestamp of the sampling output of each bucket is the timestamp of the first point of the bucket.</p><table><thead><tr><th>Function Name</th><th>Allowed Input Series Data Types</th><th>Required Attributes</th><th>Output Series Data Type</th><th>Series Data Type Description</th></tr></thead><tbody><tr><td>EQUAL_SIZE_BUCKET_AGG_SAMPLE</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td><code>proportion</code> The value range is <code>(0, 1]</code>, the default is <code>0.1</code><br><code>type</code>: The value types are <code>avg</code>, <code>max</code>, <code>min</code>, <code>sum</code>, <code>extreme</code>, <code>variance</code>, the default is <code>avg</code></td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>Returns equal bucket aggregation samples that match the sampling ratio</td></tr></tbody></table><p>Example data: <code>root.ln.wf01.wt01.temperature</code> has a total of <code>100</code> ordered data from <code>0.0-99.0</code>, and the test data is randomly sampled in equal buckets.</p><p>Sql:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> equal_size_bucket_agg_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;type&#39;</span><span class="token operator">=</span><span class="token string">&#39;avg&#39;</span><span class="token punctuation">,</span><span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> agg_avg<span class="token punctuation">,</span> equal_size_bucket_agg_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;type&#39;</span><span class="token operator">=</span><span class="token string">&#39;max&#39;</span><span class="token punctuation">,</span><span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> agg_max<span class="token punctuation">,</span> equal_size_bucket_agg_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span><span class="token string">&#39;type&#39;</span><span class="token operator">=</span><span class="token string">&#39;min&#39;</span><span class="token punctuation">,</span><span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> agg_min<span class="token punctuation">,</span> equal_size_bucket_agg_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;type&#39;</span><span class="token operator">=</span><span class="token string">&#39;sum&#39;</span><span class="token punctuation">,</span><span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> agg_sum<span class="token punctuation">,</span> equal_size_bucket_agg_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;type&#39;</span><span class="token operator">=</span><span class="token string">&#39;extreme&#39;</span><span class="token punctuation">,</span><span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> agg_extreme<span class="token punctuation">,</span> equal_size_bucket_agg_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;type&#39;</span><span class="token operator">=</span><span class="token string">&#39;variance&#39;</span><span class="token punctuation">,</span><span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> agg_variance <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Result:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------+-------+-------+-------+-----------+------------+
|                         Time|          agg_avg|agg_max|agg_min|agg_sum|agg_extreme|agg_variance|
+-----------------------------+-----------------+-------+-------+-------+-----------+------------+
|1970-01-01T08:00:00.000+08:00|              4.5|    9.0|    0.0|   45.0|        9.0|        8.25|
|1970-01-01T08:00:00.010+08:00|             14.5|   19.0|   10.0|  145.0|       19.0|        8.25|
|1970-01-01T08:00:00.020+08:00|             24.5|   29.0|   20.0|  245.0|       29.0|        8.25|
|1970-01-01T08:00:00.030+08:00|             34.5|   39.0|   30.0|  345.0|       39.0|        8.25|
|1970-01-01T08:00:00.040+08:00|             44.5|   49.0|   40.0|  445.0|       49.0|        8.25|
|1970-01-01T08:00:00.050+08:00|             54.5|   59.0|   50.0|  545.0|       59.0|        8.25|
|1970-01-01T08:00:00.060+08:00|             64.5|   69.0|   60.0|  645.0|       69.0|        8.25|
|1970-01-01T08:00:00.070+08:00|74.50000000000001|   79.0|   70.0|  745.0|       79.0|        8.25|
|1970-01-01T08:00:00.080+08:00|             84.5|   89.0|   80.0|  845.0|       89.0|        8.25|
|1970-01-01T08:00:00.090+08:00|             94.5|   99.0|   90.0|  945.0|       99.0|        8.25|
+-----------------------------+-----------------+-------+-------+-------+-----------+------------+
Total line number = 10
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 class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="equal-size-bucket-m4-sample" tabindex="-1"><a class="header-anchor" href="#equal-size-bucket-m4-sample"><span>Equal Size Bucket M4 Sample</span></a></h3><p>The input sequence is sampled using the M4 sampling method. That is to sample the head, tail, min and max values for each bucket.</p><table><thead><tr><th>Function Name</th><th>Allowed Input Series Data Types</th><th>Required Attributes</th><th>Output Series Data Type</th><th>Series Data Type Description</th></tr></thead><tbody><tr><td>EQUAL_SIZE_BUCKET_M4_SAMPLE</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td><code>proportion</code> The value range is <code>(0, 1]</code>, the default is <code>0.1</code></td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>Returns equal bucket M4 samples that match the sampling ratio</td></tr></tbody></table><p>Example data: <code>root.ln.wf01.wt01.temperature</code> has a total of <code>100</code> ordered data from <code>0.0-99.0</code>, and the test data is randomly sampled in equal buckets.</p><p>Sql:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> equal_size_bucket_m4_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> M4_sample <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Result:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+---------+
|                         Time|M4_sample|
+-----------------------------+---------+
|1970-01-01T08:00:00.000+08:00|      0.0|
|1970-01-01T08:00:00.001+08:00|      1.0|
|1970-01-01T08:00:00.038+08:00|     38.0|
|1970-01-01T08:00:00.039+08:00|     39.0|
|1970-01-01T08:00:00.040+08:00|     40.0|
|1970-01-01T08:00:00.041+08:00|     41.0|
|1970-01-01T08:00:00.078+08:00|     78.0|
|1970-01-01T08:00:00.079+08:00|     79.0|
|1970-01-01T08:00:00.080+08:00|     80.0|
|1970-01-01T08:00:00.081+08:00|     81.0|
|1970-01-01T08:00:00.098+08:00|     98.0|
|1970-01-01T08:00:00.099+08:00|     99.0|
+-----------------------------+---------+
Total line number = 12
It costs 0.065s
</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><h4 id="equal-size-bucket-outlier-sample" tabindex="-1"><a class="header-anchor" href="#equal-size-bucket-outlier-sample"><span>Equal Size Bucket Outlier Sample</span></a></h4><p>This function samples the input sequence with equal number of bucket outliers, that is, according to the downsampling ratio given by the user and the number of samples in the bucket, the input sequence is divided into several buckets according to a fixed number of points. Sampling by the given outlier sampling method within each bucket.</p><table><thead><tr><th>Function Name</th><th>Allowed Input Series Data Types</th><th>Required Attributes</th><th>Output Series Data Type</th><th>Series Data Type Description</th></tr></thead><tbody><tr><td>EQUAL_SIZE_BUCKET_OUTLIER_SAMPLE</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>The value range of <code>proportion</code> is <code>(0, 1]</code>, the default is <code>0.1</code><br> The value of <code>type</code> is <code>avg</code> or <code>stendis</code> or <code>cos</code> or <code>prenextdis</code>, the default is <code>avg</code> <br>The value of <code>number</code> should be greater than 0, the default is <code>3</code></td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>Returns outlier samples in equal buckets that match the sampling ratio and the number of samples in the bucket</td></tr></tbody></table><p>Parameter Description</p><ul><li><code>proportion</code>: sampling ratio</li><li><code>number</code>: the number of samples in each bucket, default <code>3</code></li><li><code>type</code>: outlier sampling method, the value is <ul><li><code>avg</code>: Take the average of the data points in the bucket, and find the <code>top number</code> farthest from the average according to the sampling ratio</li><li><code>stendis</code>: Take the vertical distance between each data point in the bucket and the first and last data points of the bucket to form a straight line, and according to the sampling ratio, find the <code>top number</code> with the largest distance</li><li><code>cos</code>: Set a data point in the bucket as b, the data point on the left of b as a, and the data point on the right of b as c, then take the cosine value of the angle between the ab and bc vectors. The larger the angle, the more likely it is an outlier. Find the <code>top number</code> with the smallest cos value</li><li><code>prenextdis</code>: Let a data point in the bucket be b, the data point to the left of b is a, and the data point to the right of b is c, then take the sum of the lengths of ab and bc as the yardstick, the larger the sum, the more likely it is to be an outlier, and find the <code>top number</code> with the largest sum value</li></ul></li></ul><p>Example data: <code>root.ln.wf01.wt01.temperature</code> has a total of <code>100</code> ordered data from <code>0.0-99.0</code>. Among them, in order to add outliers, we make the number modulo 5 equal to 0 increment by 100.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; select temperature from root.ln.wf01.wt01;
+-----------------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.temperature|
+-----------------------------+-----------------------------+
|1970-01-01T08:00:00.000+08:00|                          0.0|
|1970-01-01T08:00:00.001+08:00|                          1.0|
|1970-01-01T08:00:00.002+08:00|                          2.0|
|1970-01-01T08:00:00.003+08:00|                          3.0|
|1970-01-01T08:00:00.004+08:00|                          4.0|
|1970-01-01T08:00:00.005+08:00|                        105.0|
|1970-01-01T08:00:00.006+08:00|                          6.0|
|1970-01-01T08:00:00.007+08:00|                          7.0|
|1970-01-01T08:00:00.008+08:00|                          8.0|
|1970-01-01T08:00:00.009+08:00|                          9.0|
|1970-01-01T08:00:00.010+08:00|                         10.0|
|1970-01-01T08:00:00.011+08:00|                         11.0|
|1970-01-01T08:00:00.012+08:00|                         12.0|
|1970-01-01T08:00:00.013+08:00|                         13.0|
|1970-01-01T08:00:00.014+08:00|                         14.0|
|1970-01-01T08:00:00.015+08:00|                        115.0|
|1970-01-01T08:00:00.016+08:00|                         16.0|
|.............................|.............................|
|1970-01-01T08:00:00.092+08:00|                         92.0|
|1970-01-01T08:00:00.093+08:00|                         93.0|
|1970-01-01T08:00:00.094+08:00|                         94.0|
|1970-01-01T08:00:00.095+08:00|                        195.0|
|1970-01-01T08:00:00.096+08:00|                         96.0|
|1970-01-01T08:00:00.097+08:00|                         97.0|
|1970-01-01T08:00:00.098+08:00|                         98.0|
|1970-01-01T08:00:00.099+08:00|                         99.0|
+-----------------------------+-----------------------------+
</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 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>Sql:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> equal_size_bucket_outlier_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;type&#39;</span><span class="token operator">=</span><span class="token string">&#39;avg&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;number&#39;</span><span class="token operator">=</span><span class="token string">&#39;2&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> outlier_avg_sample<span class="token punctuation">,</span> equal_size_bucket_outlier_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;type&#39;</span><span class="token operator">=</span><span class="token string">&#39;stendis&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;number&#39;</span><span class="token operator">=</span><span class="token string">&#39;2&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> outlier_stendis_sample<span class="token punctuation">,</span> equal_size_bucket_outlier_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;type&#39;</span><span class="token operator">=</span><span class="token string">&#39;cos&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;number&#39;</span><span class="token operator">=</span><span class="token string">&#39;2&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> outlier_cos_sample<span class="token punctuation">,</span> equal_size_bucket_outlier_sample<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;proportion&#39;</span><span class="token operator">=</span><span class="token string">&#39;0.1&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;type&#39;</span><span class="token operator">=</span><span class="token string">&#39;prenextdis&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;number&#39;</span><span class="token operator">=</span><span class="token string">&#39;2&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> outlier_prenextdis_sample <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Result:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+------------------+----------------------+------------------+-------------------------+
|                         Time|outlier_avg_sample|outlier_stendis_sample|outlier_cos_sample|outlier_prenextdis_sample|
+-----------------------------+------------------+----------------------+------------------+-------------------------+
|1970-01-01T08:00:00.005+08:00|             105.0|                 105.0|             105.0|                    105.0|
|1970-01-01T08:00:00.015+08:00|             115.0|                 115.0|             115.0|                    115.0|
|1970-01-01T08:00:00.025+08:00|             125.0|                 125.0|             125.0|                    125.0|
|1970-01-01T08:00:00.035+08:00|             135.0|                 135.0|             135.0|                    135.0|
|1970-01-01T08:00:00.045+08:00|             145.0|                 145.0|             145.0|                    145.0|
|1970-01-01T08:00:00.055+08:00|             155.0|                 155.0|             155.0|                    155.0|
|1970-01-01T08:00:00.065+08:00|             165.0|                 165.0|             165.0|                    165.0|
|1970-01-01T08:00:00.075+08:00|             175.0|                 175.0|             175.0|                    175.0|
|1970-01-01T08:00:00.085+08:00|             185.0|                 185.0|             185.0|                    185.0|
|1970-01-01T08:00:00.095+08:00|             195.0|                 195.0|             195.0|                    195.0|
+-----------------------------+------------------+----------------------+------------------+-------------------------+
Total line number = 10
It costs 0.041s
</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></div><h2 id="m4-function" tabindex="-1"><a class="header-anchor" href="#m4-function"><span>M4 Function</span></a></h2><p>M4 is used to sample the <code>first, last, bottom, top</code> points for each sliding window:</p><ul><li>the first point is the point with the <strong>m</strong>inimal time;</li><li>the last point is the point with the <strong>m</strong>aximal time;</li><li>the bottom point is the point with the <strong>m</strong>inimal value (if there are multiple such points, M4 returns one of them);</li><li>the top point is the point with the <strong>m</strong>aximal value (if there are multiple such points, M4 returns one of them).</li></ul><img src="https://alioss.timecho.com/docs/img/github/198178733-a0919d17-0663-4672-9c4f-1efad6f463c2.png" alt="image" style="zoom:50%;"><table><thead><tr><th>Function Name</th><th>Allowed Input Series Data Types</th><th>Attributes</th><th>Output Series Data Type</th><th>Series Data Type Description</th></tr></thead><tbody><tr><td>M4</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>Different attributes used by the size window and the time window. The size window uses attributes <code>windowSize</code> and <code>slidingStep</code>. The time window uses attributes <code>timeInterval</code>, <code>slidingStep</code>, <code>displayWindowBegin</code>, and <code>displayWindowEnd</code>. More details see below.</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>Returns the <code>first, last, bottom, top</code> points in each sliding window. M4 sorts and deduplicates the aggregated points within the window before outputting them.</td></tr></tbody></table><h3 id="attributes" tabindex="-1"><a class="header-anchor" href="#attributes"><span>Attributes</span></a></h3><p><strong>(1) Attributes for the size window:</strong></p><ul><li><code>windowSize</code>: The number of points in a window. Int data type. <strong>Required</strong>.</li><li><code>slidingStep</code>: Slide a window by the number of points. Int data type. Optional. If not set, default to the same as <code>windowSize</code>.</li></ul><img src="https://alioss.timecho.com/docs/img/github/198181449-00d563c8-7bce-4ecd-a031-ec120ca42c3f.png" alt="image" style="zoom:50%;"><p><em>(image source: <a href="https://iotdb.apache.org/UserGuide/Master/Process-Data/UDF-User-Defined-Function.html#udtf-user-defined-timeseries-generating-function" target="_blank" rel="noopener noreferrer">https://iotdb.apache.org/UserGuide/Master/Process-Data/UDF-User-Defined-Function.html#udtf-user-defined-timeseries-generating-function<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>)</em></p><p><strong>(2) Attributes for the time window:</strong></p><ul><li><code>timeInterval</code>: The time interval length of a window. Long data type. <strong>Required</strong>.</li><li><code>slidingStep</code>: Slide a window by the time length. Long data type. Optional. If not set, default to the same as <code>timeInterval</code>.</li><li><code>displayWindowBegin</code>: The starting position of the window (included). Long data type. Optional. If not set, default to Long.MIN_VALUE, meaning using the time of the first data point of the input time series as the starting position of the window.</li><li><code>displayWindowEnd</code>: End time limit (excluded, essentially playing the same role as <code>WHERE time &lt; displayWindowEnd</code>). Long data type. Optional. If not set, default to Long.MAX_VALUE, meaning there is no additional end time limit other than the end of the input time series itself.</li></ul><img src="https://alioss.timecho.com/docs/img/github/198183015-93b56644-3330-4acf-ae9e-d718a02b5f4c.png" alt="groupBy window" style="zoom:67%;"><p><em>(image source: <a href="https://iotdb.apache.org/UserGuide/Master/Query-Data/Aggregate-Query.html#downsampling-aggregate-query" target="_blank" rel="noopener noreferrer">https://iotdb.apache.org/UserGuide/Master/Query-Data/Aggregate-Query.html#downsampling-aggregate-query<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>)</em></p><h3 id="examples" tabindex="-1"><a class="header-anchor" href="#examples"><span>Examples</span></a></h3><p>Input series:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token operator">+</span><span class="token comment">-----------------------------+------------------+</span>
<span class="token operator">|</span>                         <span class="token keyword">Time</span><span class="token operator">|</span>root<span class="token punctuation">.</span>vehicle<span class="token punctuation">.</span>d1<span class="token punctuation">.</span>s1<span class="token operator">|</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+------------------+</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.001</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>               <span class="token number">5.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.002</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>              <span class="token number">15.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.005</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>              <span class="token number">10.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.008</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>               <span class="token number">8.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.010</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>              <span class="token number">30.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.020</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>              <span class="token number">20.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.025</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>               <span class="token number">8.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.027</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>              <span class="token number">20.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.030</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>              <span class="token number">40.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.033</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>               <span class="token number">9.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.035</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>              <span class="token number">10.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.040</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>              <span class="token number">20.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.045</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>              <span class="token number">30.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.052</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>               <span class="token number">8.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.054</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>              <span class="token number">18.0</span><span class="token operator">|</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+------------------+</span>
</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 class="line-number"></div></div></div><p>SQL for query1:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> M4<span class="token punctuation">(</span>s1<span class="token punctuation">,</span><span class="token string">&#39;timeInterval&#39;</span><span class="token operator">=</span><span class="token string">&#39;25&#39;</span><span class="token punctuation">,</span><span class="token string">&#39;displayWindowBegin&#39;</span><span class="token operator">=</span><span class="token string">&#39;0&#39;</span><span class="token punctuation">,</span><span class="token string">&#39;displayWindowEnd&#39;</span><span class="token operator">=</span><span class="token string">&#39;100&#39;</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>vehicle<span class="token punctuation">.</span>d1
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Output1:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token operator">+</span><span class="token comment">-----------------------------+-----------------------------------------------------------------------------------------------+</span>
<span class="token operator">|</span>                         <span class="token keyword">Time</span><span class="token operator">|</span>M4<span class="token punctuation">(</span>root<span class="token punctuation">.</span>vehicle<span class="token punctuation">.</span>d1<span class="token punctuation">.</span>s1<span class="token punctuation">,</span> <span class="token string">&quot;timeInterval&quot;</span><span class="token operator">=</span><span class="token string">&quot;25&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;displayWindowBegin&quot;</span><span class="token operator">=</span><span class="token string">&quot;0&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;displayWindowEnd&quot;</span><span class="token operator">=</span><span class="token string">&quot;100&quot;</span><span class="token punctuation">)</span><span class="token operator">|</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+-----------------------------------------------------------------------------------------------+</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.001</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                                                                            <span class="token number">5.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.010</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                                                                           <span class="token number">30.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.020</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                                                                           <span class="token number">20.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.025</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                                                                            <span class="token number">8.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.030</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                                                                           <span class="token number">40.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.045</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                                                                           <span class="token number">30.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.052</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                                                                            <span class="token number">8.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.054</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                                                                           <span class="token number">18.0</span><span class="token operator">|</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+-----------------------------------------------------------------------------------------------+</span>
Total line number <span class="token operator">=</span> <span class="token number">8</span>
</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>SQL for query2:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> M4<span class="token punctuation">(</span>s1<span class="token punctuation">,</span><span class="token string">&#39;windowSize&#39;</span><span class="token operator">=</span><span class="token string">&#39;10&#39;</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>vehicle<span class="token punctuation">.</span>d1
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Output2:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token operator">+</span><span class="token comment">-----------------------------+-----------------------------------------+</span>
<span class="token operator">|</span>                         <span class="token keyword">Time</span><span class="token operator">|</span>M4<span class="token punctuation">(</span>root<span class="token punctuation">.</span>vehicle<span class="token punctuation">.</span>d1<span class="token punctuation">.</span>s1<span class="token punctuation">,</span> <span class="token string">&quot;windowSize&quot;</span><span class="token operator">=</span><span class="token string">&quot;10&quot;</span><span class="token punctuation">)</span><span class="token operator">|</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+-----------------------------------------+</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.001</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                      <span class="token number">5.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.030</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                     <span class="token number">40.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.033</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                      <span class="token number">9.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.035</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                     <span class="token number">10.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.045</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                     <span class="token number">30.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.052</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                      <span class="token number">8.0</span><span class="token operator">|</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.054</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span>                                     <span class="token number">18.0</span><span class="token operator">|</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+-----------------------------------------+</span>
Total line number <span class="token operator">=</span> <span class="token number">7</span>
</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></div><h3 id="suggested-use-cases" tabindex="-1"><a class="header-anchor" href="#suggested-use-cases"><span>Suggested Use Cases</span></a></h3><p><strong>(1) Use Case: Extreme-point-preserving downsampling</strong></p><p>As M4 aggregation selects the <code>first, last, bottom, top</code> points for each window, M4 usually preserves extreme points and thus patterns better than other downsampling methods such as Piecewise Aggregate Approximation (PAA). Therefore, if you want to downsample the time series while preserving extreme points, you may give M4 a try.</p><p><strong>(2) Use case: Error-free two-color line chart visualization of large-scale time series using reduced data</strong></p><p>Refer to paper: <a href="http://www.vldb.org/pvldb/vol7/p797-jugel.pdf" target="_blank" rel="noopener noreferrer">&quot;M4: A Visualization-Oriented Time Series Data Aggregation&quot;<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>.</p><p>Given a chart of <code>w*h</code> pixels, suppose the visualization time range of the time series root.vehicle.d1.s1 is <code>[tqs,tqe)</code>(in this use case please extend tqe to make sure (tqe-tqs) is divisible by w), the points that fall within the <code>i</code>-th time span <code>Ii=[tqs+(tqe-tqs)/w*(i-1),tqs+(tqe-tqs)/w*i)</code> will be drawn on the <code>i</code>-th pixel column, i=1,2,...,w.</p><p>Therefore, from a visualization-driven perspective, use the sql: <code>&quot;select M4(s1,&#39;timeInterval&#39;=&#39;(tqe-tqs)/w&#39;,&#39;displayWindowBegin&#39;=&#39;tqs&#39;,&#39;displayWindowEnd&#39;=&#39;tqe&#39;) from root.vehicle.d1&quot;</code> to sample the <code>first, last, bottom, top</code> points for each time span. The resulting series has no more than <code>4*w</code> points, a big reduction compared to the original large-scale time series. The line chart drawn from the reduced data is identical that to that drawn from the original data (pixel-level consistency).</p><h3 id="comparison-with-other-sql" tabindex="-1"><a class="header-anchor" href="#comparison-with-other-sql"><span>Comparison with Other SQL</span></a></h3><table><thead><tr><th>SQL</th><th>Whether support M4 aggregation</th><th>Sliding window type</th><th>Example</th><th>Docs</th></tr></thead><tbody><tr><td>1. native built-in aggregate functions with Group By clause</td><td>No. Lack <code>BOTTOM_TIME</code> and <code>TOP_TIME</code>, which are respectively the time of the points that have the mininum and maximum value.</td><td>Time Window</td><td><code>select count(status), max_value(temperature) from root.ln.wf01.wt01 group by ([2017-11-01 00:00:00, 2017-11-07 23:00:00), 3h, 1d)</code></td><td><a href="https://iotdb.apache.org/UserGuide/Master/Query-Data/Aggregate-Query.html#built-in-aggregate-functions" target="_blank" rel="noopener noreferrer">https://iotdb.apache.org/UserGuide/Master/Query-Data/Aggregate-Query.html#built-in-aggregate-functions<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> <br><a href="https://iotdb.apache.org/UserGuide/Master/Query-Data/Aggregate-Query.html#downsampling-aggregate-query" target="_blank" rel="noopener noreferrer">https://iotdb.apache.org/UserGuide/Master/Query-Data/Aggregate-Query.html#downsampling-aggregate-query<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></td></tr><tr><td>2. EQUAL_SIZE_BUCKET_M4_SAMPLE (built-in UDF)</td><td>Yes*</td><td>Size Window. <code>windowSize = 4*(int)(1/proportion)</code></td><td><code>select equal_size_bucket_m4_sample(temperature, &#39;proportion&#39;=&#39;0.1&#39;) as M4_sample from root.ln.wf01.wt01</code></td><td><a href="https://iotdb.apache.org/UserGuide/Master/Query-Data/Select-Expression.html#time-series-generating-functions" target="_blank" rel="noopener noreferrer">https://iotdb.apache.org/UserGuide/Master/Query-Data/Select-Expression.html#time-series-generating-functions<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></td></tr><tr><td><strong>3. M4 (built-in UDF)</strong></td><td>Yes*</td><td>Size Window, Time Window</td><td>(1) Size Window: <code>select M4(s1,&#39;windowSize&#39;=&#39;10&#39;) from root.vehicle.d1</code> <br>(2) Time Window: <code>select M4(s1,&#39;timeInterval&#39;=&#39;25&#39;,&#39;displayWindowBegin&#39;=&#39;0&#39;,&#39;displayWindowEnd&#39;=&#39;100&#39;) from root.vehicle.d1</code></td><td>refer to this doc</td></tr><tr><td>4. extend native built-in aggregate functions with Group By clause to support M4 aggregation</td><td>not implemented</td><td>not implemented</td><td>not implemented</td><td>not implemented</td></tr></tbody></table><p>Further compare <code>EQUAL_SIZE_BUCKET_M4_SAMPLE</code> and <code>M4</code>:</p><p><strong>(1) Different M4 aggregation definition:</strong></p><p>For each window, <code>EQUAL_SIZE_BUCKET_M4_SAMPLE</code> extracts the top and bottom points from points <strong>EXCLUDING</strong> the first and last points.</p><p>In contrast, <code>M4</code> extracts the top and bottom points from points <strong>INCLUDING</strong> the first and last points, which is more consistent with the semantics of <code>max_value</code> and <code>min_value</code> stored in metadata.</p><p>It is worth noting that both functions sort and deduplicate the aggregated points in a window before outputting them to the collectors.</p><p><strong>(2) Different sliding windows:</strong></p><p><code>EQUAL_SIZE_BUCKET_M4_SAMPLE</code> uses SlidingSizeWindowAccessStrategy and <strong>indirectly</strong> controls sliding window size by sampling proportion. The conversion formula is <code>windowSize = 4*(int)(1/proportion)</code>.</p><p><code>M4</code> supports two types of sliding window: SlidingSizeWindowAccessStrategy and SlidingTimeWindowAccessStrategy. <code>M4</code> <strong>directly</strong> controls the window point size or time length using corresponding parameters.</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/V1.0.x/Operators-Functions/Sample.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/V1.0.x/Operators-Functions/Variation-Trend.html" aria-label="Variation Trend"><div class="hint"><span class="arrow start"></span>Prev</div><div class="link"><!---->Variation Trend</div></a><a class="route-link nav-link next" href="/UserGuide/V1.0.x/Operators-Functions/Time-Series.html" aria-label="Time-Series"><div class="hint">Next<span class="arrow end"></span></div><div class="link">Time-Series<!----></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 © 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>
    <script type="module" src="/assets/app-B-0YFdX2.js" defer></script>
  </body>
</html>