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end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Reference</span><span class="arrow end"></span></button><!----></section></li></ul><!--[--><!----><!--]--></aside><!--[--><main class="page" id="main-content"><!--[--><!----><nav class="breadcrumb disable"></nav><div class="page-title"><h1><!---->Lambda Expression</h1><div class="page-info"><!----><!----><!----><!----><span class="page-reading-time-info" aria-label="Reading Time"><svg xmlns="http://www.w3.org/2000/svg" class="icon timer-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="timer icon"><path d="M799.387 122.15c4.402-2.978 7.38-7.897 7.38-13.463v-1.165c0-8.933-7.38-16.312-16.312-16.312H256.33c-8.933 0-16.311 7.38-16.311 16.312v1.165c0 5.825 2.977 10.874 7.637 13.592 4.143 194.44 97.22 354.963 220.201 392.763-122.204 37.542-214.893 196.511-220.2 389.397-4.661 5.049-7.638 11.651-7.638 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--><h1 id="lambda-expression" tabindex="-1"><a class="header-anchor" href="#lambda-expression" aria-hidden="true">#</a> Lambda Expression</h1><h2 id="jexl-function" tabindex="-1"><a class="header-anchor" href="#jexl-function" aria-hidden="true">#</a> JEXL Function</h2><p>Java Expression Language (JEXL) is an expression language engine. We use JEXL to extend UDFs, which are implemented on the command line with simple lambda expressions. See the link for <a href="https://commons.apache.org/proper/commons-jexl/apidocs/org/apache/commons/jexl3/package-summary.html#customization" target="_blank" rel="noopener noreferrer">operators supported in jexl lambda expressions<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><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>JEXL</td><td>INT32 / INT64 / FLOAT / DOUBLE / TEXT / BOOLEAN</td><td><code>expr</code> is a lambda expression that supports standard one or multi arguments in the form <code>x -&gt; {...}</code> or <code>(x, y, z) -&gt; {...}</code>, e.g. <code> x -&gt; {x * 2}</code>, <code>(x, y, z) -&gt; {x + y * z}</code></td><td>INT32 / INT64 / FLOAT / DOUBLE / TEXT / BOOLEAN</td><td>Returns the input time series transformed by a lambda expression</td></tr></tbody></table><h4 id="demonstrate" tabindex="-1"><a class="header-anchor" href="#demonstrate" aria-hidden="true">#</a> Demonstrate</h4><p>Example data: <code>root.ln.wf01.wt01.temperature</code>, <code>root.ln.wf01.wt01.st</code>, <code>root.ln.wf01.wt01.str</code> a total of <code>11</code> data.</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>IoTDB&gt; select * from root.ln.wf01.wt01;
+-----------------------------+---------------------+--------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.str|root.ln.wf01.wt01.st|root.ln.wf01.wt01.temperature|
+-----------------------------+---------------------+--------------------+-----------------------------+
|1970-01-01T08:00:00.000+08:00|                  str|                10.0|                          0.0|
|1970-01-01T08:00:00.001+08:00|                  str|                20.0|                          1.0|
|1970-01-01T08:00:00.002+08:00|                  str|                30.0|                          2.0|
|1970-01-01T08:00:00.003+08:00|                  str|                40.0|                          3.0|
|1970-01-01T08:00:00.004+08:00|                  str|                50.0|                          4.0|
|1970-01-01T08:00:00.005+08:00|                  str|                60.0|                          5.0|
|1970-01-01T08:00:00.006+08:00|                  str|                70.0|                          6.0|
|1970-01-01T08:00:00.007+08:00|                  str|                80.0|                          7.0|
|1970-01-01T08:00:00.008+08:00|                  str|                90.0|                          8.0|
|1970-01-01T08:00:00.009+08:00|                  str|               100.0|                          9.0|
|1970-01-01T08:00:00.010+08:00|                  str|               110.0|                         10.0|
+-----------------------------+---------------------+--------------------+-----------------------------+
</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></div><p>Sql:</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">select</span> jexl<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;expr&#39;</span><span class="token operator">=</span><span class="token string">&#39;x -&gt; {x + x}&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> jexl1<span class="token punctuation">,</span> jexl<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;expr&#39;</span><span class="token operator">=</span><span class="token string">&#39;x -&gt; {x * 3}&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> jexl2<span class="token punctuation">,</span> jexl<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;expr&#39;</span><span class="token operator">=</span><span class="token string">&#39;x -&gt; {x * x}&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> jexl3<span class="token punctuation">,</span> jexl<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> <span class="token string">&#39;expr&#39;</span><span class="token operator">=</span><span class="token string">&#39;x -&gt; {multiply(x, 100)}&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> jexl4<span class="token punctuation">,</span> jexl<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> st<span class="token punctuation">,</span> <span class="token string">&#39;expr&#39;</span><span class="token operator">=</span><span class="token string">&#39;(x, y) -&gt; {x + y}&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> jexl5<span class="token punctuation">,</span> jexl<span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> st<span class="token punctuation">,</span> str<span class="token punctuation">,</span> <span class="token string">&#39;expr&#39;</span><span class="token operator">=</span><span class="token string">&#39;(x, y, z) -&gt; {x + y + z}&#39;</span><span class="token punctuation">)</span> <span class="token keyword">as</span> jexl6 <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><span class="token identifier"><span class="token punctuation">`</span><span class="token punctuation">`</span></span><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"><pre class="language-text"><code>+-----------------------------+-----+-----+-----+------+-----+--------+
|                         Time|jexl1|jexl2|jexl3| jexl4|jexl5|   jexl6|
+-----------------------------+-----+-----+-----+------+-----+--------+
|1970-01-01T08:00:00.000+08:00|  0.0|  0.0|  0.0|   0.0| 10.0| 10.0str|
|1970-01-01T08:00:00.001+08:00|  2.0|  3.0|  1.0| 100.0| 21.0| 21.0str|
|1970-01-01T08:00:00.002+08:00|  4.0|  6.0|  4.0| 200.0| 32.0| 32.0str|
|1970-01-01T08:00:00.003+08:00|  6.0|  9.0|  9.0| 300.0| 43.0| 43.0str|
|1970-01-01T08:00:00.004+08:00|  8.0| 12.0| 16.0| 400.0| 54.0| 54.0str|
|1970-01-01T08:00:00.005+08:00| 10.0| 15.0| 25.0| 500.0| 65.0| 65.0str|
|1970-01-01T08:00:00.006+08:00| 12.0| 18.0| 36.0| 600.0| 76.0| 76.0str|
|1970-01-01T08:00:00.007+08:00| 14.0| 21.0| 49.0| 700.0| 87.0| 87.0str|
|1970-01-01T08:00:00.008+08:00| 16.0| 24.0| 64.0| 800.0| 98.0| 98.0str|
|1970-01-01T08:00:00.009+08:00| 18.0| 27.0| 81.0| 900.0|109.0|109.0str|
|1970-01-01T08:00:00.010+08:00| 20.0| 30.0|100.0|1000.0|120.0|120.0str|
+-----------------------------+-----+-----+-----+------+-----+--------+
Total line number = 11
It costs 0.118s
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