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       </script><title>采样函数 | IoTDB Website</title><meta name="description" content="采样函数 等数量分桶降采样函数 本函数对输入序列进行等数量分桶采样，即根据用户给定的降采样比例和降采样方法将输入序列按固定点数等分为若干桶。在每个桶内通过给定的采样方法进行采样。 等数量分桶随机采样 函数简介 对等数量分桶后，桶内进行随机采样。 使用示例 输入序列:root.ln.wf01.wt01.temperature从0.0-99.0共100条数...">
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href="#等数量分桶随机采样">等数量分桶随机采样</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#等数量分桶聚合采样">等数量分桶聚合采样</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#等数量分桶-m4-采样">等数量分桶 M4 采样</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#等数量分桶离群值采样">等数量分桶离群值采样</a></li><!----><!--]--></ul></li><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#m4函数">M4函数</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#函数简介-4">函数简介</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#属性参数">属性参数</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#使用示例-4">使用示例</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#推荐的使用场景">推荐的使用场景</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#和其它sql的功能比较">和其它SQL的功能比较</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="采样函数" tabindex="-1"><a class="header-anchor" href="#采样函数"><span>采样函数</span></a></h1><h2 id="等数量分桶降采样函数" tabindex="-1"><a class="header-anchor" href="#等数量分桶降采样函数"><span>等数量分桶降采样函数</span></a></h2><p>本函数对输入序列进行等数量分桶采样，即根据用户给定的降采样比例和降采样方法将输入序列按固定点数等分为若干桶。在每个桶内通过给定的采样方法进行采样。</p><h3 id="等数量分桶随机采样" tabindex="-1"><a class="header-anchor" href="#等数量分桶随机采样"><span>等数量分桶随机采样</span></a></h3><h4 id="函数简介" tabindex="-1"><a class="header-anchor" href="#函数简介"><span>函数简介</span></a></h4><p>对等数量分桶后，桶内进行随机采样。</p><table><thead><tr><th>函数名</th><th>可接收的输入序列类型</th><th>必要的属性参数</th><th>输出序列类型</th><th>功能类型</th></tr></thead><tbody><tr><td>EQUAL_SIZE_BUCKET_RANDOM_SAMPLE</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>降采样比例 <code>proportion</code>，取值范围为<code>(0, 1]</code>，默认为<code>0.1</code></td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>返回符合采样比例的等分桶随机采样</td></tr></tbody></table><h4 id="使用示例" tabindex="-1"><a class="header-anchor" href="#使用示例"><span>使用示例</span></a></h4><p>输入序列:<code>root.ln.wf01.wt01.temperature</code>从<code>0.0-99.0</code>共<code>100</code>条数据。</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>结果:</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="等数量分桶聚合采样" tabindex="-1"><a class="header-anchor" href="#等数量分桶聚合采样"><span>等数量分桶聚合采样</span></a></h3><h4 id="函数简介-1" tabindex="-1"><a class="header-anchor" href="#函数简介-1"><span>函数简介</span></a></h4><p>采用聚合采样法对输入序列进行采样，用户需要另外提供一个聚合函数参数即</p><ul><li><code>type</code>：聚合类型，取值为<code>avg</code>或<code>max</code>或<code>min</code>或<code>sum</code>或<code>extreme</code>或<code>variance</code>。在缺省情况下，采用<code>avg</code>。其中<code>extreme</code>表示等分桶中，绝对值最大的值。<code>variance</code>表示采样等分桶中的方差。</li></ul><p>每个桶采样输出的时间戳为这个桶第一个点的时间戳</p><table><thead><tr><th>函数名</th><th>可接收的输入序列类型</th><th>必要的属性参数</th><th>输出序列类型</th><th>功能类型</th></tr></thead><tbody><tr><td>EQUAL_SIZE_BUCKET_AGG_SAMPLE</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td><code>proportion</code>取值范围为<code>(0, 1]</code>，默认为<code>0.1</code><br><code>type</code>:取值类型有<code>avg</code>, <code>max</code>, <code>min</code>, <code>sum</code>, <code>extreme</code>, <code>variance</code>, 默认为<code>avg</code></td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>返回符合采样比例的等分桶聚合采样</td></tr></tbody></table><h4 id="使用示例-1" tabindex="-1"><a class="header-anchor" href="#使用示例-1"><span>使用示例</span></a></h4><p>输入序列:<code>root.ln.wf01.wt01.temperature</code>从<code>0.0-99.0</code>共<code>100</code>条有序数据，同等分桶随机采样的测试数据。</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>结果:</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="等数量分桶-m4-采样" tabindex="-1"><a class="header-anchor" href="#等数量分桶-m4-采样"><span>等数量分桶 M4 采样</span></a></h3><h4 id="函数简介-2" tabindex="-1"><a class="header-anchor" href="#函数简介-2"><span>函数简介</span></a></h4><p>采用M4采样法对输入序列进行采样。即对于每个桶采样首、尾、最小和最大值。</p><table><thead><tr><th>函数名</th><th>可接收的输入序列类型</th><th>必要的属性参数</th><th>输出序列类型</th><th>功能类型</th></tr></thead><tbody><tr><td>EQUAL_SIZE_BUCKET_M4_SAMPLE</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td><code>proportion</code>取值范围为<code>(0, 1]</code>，默认为<code>0.1</code></td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>返回符合采样比例的等分桶M4采样</td></tr></tbody></table><h4 id="使用示例-2" tabindex="-1"><a class="header-anchor" href="#使用示例-2"><span>使用示例</span></a></h4><p>输入序列:<code>root.ln.wf01.wt01.temperature</code>从<code>0.0-99.0</code>共<code>100</code>条有序数据，同等分桶随机采样的测试数据。</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>结果:</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><h3 id="等数量分桶离群值采样" tabindex="-1"><a class="header-anchor" href="#等数量分桶离群值采样"><span>等数量分桶离群值采样</span></a></h3><h4 id="函数简介-3" tabindex="-1"><a class="header-anchor" href="#函数简介-3"><span>函数简介</span></a></h4><p>本函数对输入序列进行等数量分桶离群值采样，即根据用户给定的降采样比例和桶内采样个数将输入序列按固定点数等分为若干桶，在每个桶内通过给定的离群值采样方法进行采样。</p><table><thead><tr><th>函数名</th><th>可接收的输入序列类型</th><th>必要的属性参数</th><th>输出序列类型</th><th>功能类型</th></tr></thead><tbody><tr><td>EQUAL_SIZE_BUCKET_OUTLIER_SAMPLE</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td><code>proportion</code>取值范围为<code>(0, 1]</code>，默认为<code>0.1</code><br><code>type</code>取值为<code>avg</code>或<code>stendis</code>或<code>cos</code>或<code>prenextdis</code>，默认为<code>avg</code><br><code>number</code>取值应大于0，默认<code>3</code></td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>返回符合采样比例和桶内采样个数的等分桶离群值采样</td></tr></tbody></table><p>参数说明</p><ul><li><code>proportion</code>: 采样比例 <ul><li><code>number</code>: 每个桶内的采样个数，默认<code>3</code></li></ul></li><li><code>type</code>: 离群值采样方法，取值为 <ul><li><code>avg</code>: 取桶内数据点的平均值，并根据采样比例，找到距离均值最远的<code>top number</code>个</li><li><code>stendis</code>: 取桶内每一个数据点距离桶的首末数据点连成直线的垂直距离，并根据采样比例，找到距离最大的<code>top number</code>个</li><li><code>cos</code>: 设桶内一个数据点为b，b左边的数据点为a，b右边的数据点为c，则取ab与bc向量的夹角的余弦值，值越小，说明形成的角度越大，越可能是异常值。找到cos值最小的<code>top number</code>个</li><li><code>prenextdis</code>: 设桶内一个数据点为b，b左边的数据点为a，b右边的数据点为c，则取ab与bc的长度之和作为衡量标准，和越大越可能是异常值，找到最大的<code>top number</code>个</li></ul></li></ul><h4 id="使用示例-3" tabindex="-1"><a class="header-anchor" href="#使用示例-3"><span>使用示例</span></a></h4><p>测试数据:<code>root.ln.wf01.wt01.temperature</code>从<code>0.0-99.0</code>共<code>100</code>条数据，其中为了加入离群值，我们使得个位数为5的值自增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>结果:</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函数" tabindex="-1"><a class="header-anchor" href="#m4函数"><span>M4函数</span></a></h2><h3 id="函数简介-4" tabindex="-1"><a class="header-anchor" href="#函数简介-4"><span>函数简介</span></a></h3><p>M4用于在窗口内采样第一个点（<code>first</code>）、最后一个点（<code>last</code>）、最小值点（<code>bottom</code>）、最大值点（<code>top</code>）：</p><ul><li>第一个点是拥有这个窗口内最小时间戳的点；</li><li>最后一个点是拥有这个窗口内最大时间戳的点；</li><li>最小值点是拥有这个窗口内最小值的点（如果有多个这样的点，M4只返回其中一个）；</li><li>最大值点是拥有这个窗口内最大值的点（如果有多个这样的点，M4只返回其中一个）。</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>函数名</th><th>可接收的输入序列类型</th><th>属性参数</th><th>输出序列类型</th><th>功能类型</th></tr></thead><tbody><tr><td>M4</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>包含固定点数的窗口和滑动时间窗口使用不同的属性参数。包含固定点数的窗口使用属性<code>windowSize</code>和<code>slidingStep</code>。滑动时间窗口使用属性<code>timeInterval</code>、<code>slidingStep</code>、<code>displayWindowBegin</code>和<code>displayWindowEnd</code>。更多细节见下文。</td><td>INT32 / INT64 / FLOAT / DOUBLE</td><td>返回每个窗口内的第一个点（<code>first</code>）、最后一个点（<code>last</code>）、最小值点（<code>bottom</code>）、最大值点（<code>top</code>）。在一个窗口内的聚合点输出之前，M4会将它们按照时间戳递增排序并且去重。</td></tr></tbody></table><h3 id="属性参数" tabindex="-1"><a class="header-anchor" href="#属性参数"><span>属性参数</span></a></h3><p><strong>(1) 包含固定点数的窗口（SlidingSizeWindowAccessStrategy）使用的属性参数:</strong></p><ul><li><code>windowSize</code>: 一个窗口内的点数。Int数据类型。必需的属性参数。</li><li><code>slidingStep</code>: 按照设定的点数来滑动窗口。Int数据类型。可选的属性参数；如果没有设置，默认取值和<code>windowSize</code>一样。</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>(图片来源: <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) 滑动时间窗口（SlidingTimeWindowAccessStrategy）使用的属性参数:</strong></p><ul><li><code>timeInterval</code>: 一个窗口的时间长度。Long数据类型。必需的属性参数。</li><li><code>slidingStep</code>: 按照设定的时长来滑动窗口。Long数据类型。可选的属性参数；如果没有设置，默认取值和<code>timeInterval</code>一样。</li><li><code>displayWindowBegin</code>: 窗口滑动的起始时间戳位置（包含在内）。Long数据类型。可选的属性参数；如果没有设置，默认取值为Long.MIN_VALUE，意为使用输入的时间序列的第一个点的时间戳作为窗口滑动的起始时间戳位置。</li><li><code>displayWindowEnd</code>: 结束时间限制（不包含在内；本质上和<code>WHERE time &lt; displayWindowEnd</code>起的效果是一样的)。Long数据类型。可选的属性参数；如果没有设置，默认取值为Long.MAX_VALUE，意为除了输入的时间序列自身数据读取完毕之外没有增加额外的结束时间过滤条件限制。</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>(图片来源: <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="使用示例-4" tabindex="-1"><a class="header-anchor" href="#使用示例-4"><span>使用示例</span></a></h3><p>输入的时间序列：</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>查询语句1：</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>输出结果1：</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>查询语句2：</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>输出结果2：</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="推荐的使用场景" tabindex="-1"><a class="header-anchor" href="#推荐的使用场景"><span>推荐的使用场景</span></a></h3><p><strong>(1) 使用场景：保留极端点的降采样</strong></p><p>由于M4为每个窗口聚合其第一个点（<code>first</code>）、最后一个点（<code>last</code>）、最小值点（<code>bottom</code>）、最大值点（<code>top</code>），因此M4通常保留了极值点，因此比其他下采样方法（如分段聚合近似 (PAA)）能更好地保留模式。如果你想对时间序列进行下采样并且希望保留极值点，你可以试试 M4。</p><p><strong>(2) 使用场景：基于数据缩约的大规模时间序列的零误差双色折线图可视化</strong></p><p>参考论文: <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>假设屏幕画布的像素宽乘高是<code>w*h</code>，假设时间序列root.vehicle.d1.s1要可视化的时间范围是<code>[tqs,tqe)</code>（在这个使用场景里面，需要请你自行将tqe自适应调整使得(tqe-tqs)是w的整数倍），那么落在第i个时间跨度<code>Ii=[tqs+(tqe-tqs)/w*(i-1),tqs+(tqe-tqs)/w*i)</code> 内的点将会被画在第i个像素列中，i=1,2,...,w。</p><p>于是从可视化驱动的角度出发，使用查询语句：<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>，来采集每个时间跨度内的第一个点（<code>first</code>）、最后一个点（<code>last</code>）、最小值点（<code>bottom</code>）、最大值点（<code>top</code>）。最终结果点数不会超过<code>4*w</code>个，使用这些聚合点画出来的折线图与使用原始数据画出来的图在像素级别上是完全一致的。</p><h3 id="和其它sql的功能比较" tabindex="-1"><a class="header-anchor" href="#和其它sql的功能比较"><span>和其它SQL的功能比较</span></a></h3><table><thead><tr><th>SQL</th><th>是否支持M4聚合</th><th>滑动窗口类型</th><th>示例</th><th>相关文档</th></tr></thead><tbody><tr><td>1. 带有Group By子句的内置聚合函数</td><td>不支持，缺少<code>BOTTOM_TIME</code>和<code>TOP_TIME</code>，即缺少最小值点和最大值点的时间戳。</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 (内置UDF)</td><td>支持*</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 (内置UDF)</strong></td><td>支持*</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>本文档</td></tr><tr><td>4. 扩展带有Group By子句的内置聚合函数来支持M4聚合</td><td>未实施</td><td>未实施</td><td>未实施</td><td>未实施</td></tr></tbody></table><p>进一步比较<code>EQUAL_SIZE_BUCKET_M4_SAMPLE</code>和<code>M4</code>：</p><p><strong>(1) 不同的M4聚合函数定义：</strong></p><p>在每个窗口内，<code>EQUAL_SIZE_BUCKET_M4_SAMPLE</code>从排除了第一个点和最后一个点之后剩余的点中提取最小值点和最大值点。</p><p>而<code>M4</code>则是从窗口内所有点中（包括第一个点和最后一个点）提取最小值点和最大值点，这个定义与元数据中保存的<code>max_value</code>和<code>min_value</code>的语义更加一致。</p><p>值得注意的是，在一个窗口内的聚合点输出之前，<code>EQUAL_SIZE_BUCKET_M4_SAMPLE</code>和<code>M4</code>都会将它们按照时间戳递增排序并且去重。</p><p><strong>(2) 不同的滑动窗口：</strong></p><p><code>EQUAL_SIZE_BUCKET_M4_SAMPLE</code>使用SlidingSizeWindowAccessStrategy，并且通过采样比例（<code>proportion</code>）来间接控制窗口点数（<code>windowSize</code>)，转换公式是<code>windowSize = 4*(int)(1/proportion)</code>。</p><p><code>M4</code>支持两种滑动窗口：SlidingSizeWindowAccessStrategy和SlidingTimeWindowAccessStrategy，并且<code>M4</code>通过相应的参数直接控制窗口的点数或者时长。</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/zh/UserGuide/V1.0.x/Operators-Functions/Sample.md" rel="noopener noreferrer" target="_blank" aria-label="发现错误？在 GitHub 上编辑此页" 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><!--]-->发现错误？在 GitHub 上编辑此页<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span><!----></a></div><div class="vp-meta-item git-info"><div class="update-time"><span class="vp-meta-label">上次编辑于: </span><!----></div><!----></div></footer><nav class="vp-page-nav"><a class="route-link nav-link prev" href="/zh/UserGuide/V1.0.x/Operators-Functions/Variation-Trend.html" aria-label="趋势计算"><div class="hint"><span class="arrow start"></span>上一页</div><div class="link"><!---->趋势计算</div></a><a class="route-link nav-link next" href="/zh/UserGuide/V1.0.x/Operators-Functions/Time-Series.html" aria-label="时间序列处理"><div class="hint">下一页<span class="arrow end"></span></div><div class="link">时间序列处理<!----></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>
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