<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Tutorial: Transforming input data · Apache Druid</title><meta name="viewport" content="width=device-width, initial-scale=1.0"/><link rel="canonical" href="https://druid.apache.org/docs/latest/tutorials/tutorial-transform-spec.html"/><meta name="generator" content="Docusaurus"/><meta name="description" content="&lt;!--"/><meta name="docsearch:language" content="en"/><meta name="docsearch:version" content="26.0.0" /><meta property="og:title" content="Tutorial: Transforming input data · Apache Druid"/><meta property="og:type" content="website"/><meta property="og:url" content="https://druid.apache.org/index.html"/><meta property="og:description" content="&lt;!--"/><meta property="og:image" content="https://druid.apache.org/img/druid_nav.png"/><meta name="twitter:card" content="summary"/><meta name="twitter:image" content="https://druid.apache.org/img/druid_nav.png"/><link rel="shortcut icon" href="/img/favicon.png"/><link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/docsearch.js@2/dist/cdn/docsearch.min.css"/><link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.12.0/styles/default.min.css"/><script async="" src="https://www.googletagmanager.com/gtag/js?id=UA-131010415-1"></script><script>
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<p>This tutorial will demonstrate how to use transform specs to filter and transform input data during ingestion.</p>
<p>For this tutorial, we'll assume you've already downloaded Apache Druid as described in
the <a href="/docs/latest/tutorials/index.html">single-machine quickstart</a> and have it running on your local machine.</p>
<p>It will also be helpful to have finished <a href="/docs/latest/tutorials/tutorial-batch.html">Tutorial: Loading a file</a> and <a href="/docs/latest/tutorials/tutorial-query.html">Tutorial: Querying data</a>.</p>
<h2><a class="anchor" aria-hidden="true" id="sample-data"></a><a href="#sample-data" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Sample data</h2>
<p>We've included sample data for this tutorial at <code>quickstart/tutorial/transform-data.json</code>, reproduced here for convenience:</p>
<pre><code class="hljs css language-json">{<span class="hljs-attr">"timestamp"</span>:<span class="hljs-string">"2018-01-01T07:01:35Z"</span>,<span class="hljs-attr">"animal"</span>:<span class="hljs-string">"octopus"</span>,  <span class="hljs-attr">"location"</span>:<span class="hljs-number">1</span>, <span class="hljs-attr">"number"</span>:<span class="hljs-number">100</span>}
{<span class="hljs-attr">"timestamp"</span>:<span class="hljs-string">"2018-01-01T05:01:35Z"</span>,<span class="hljs-attr">"animal"</span>:<span class="hljs-string">"mongoose"</span>, <span class="hljs-attr">"location"</span>:<span class="hljs-number">2</span>,<span class="hljs-attr">"number"</span>:<span class="hljs-number">200</span>}
{<span class="hljs-attr">"timestamp"</span>:<span class="hljs-string">"2018-01-01T06:01:35Z"</span>,<span class="hljs-attr">"animal"</span>:<span class="hljs-string">"snake"</span>, <span class="hljs-attr">"location"</span>:<span class="hljs-number">3</span>, <span class="hljs-attr">"number"</span>:<span class="hljs-number">300</span>}
{<span class="hljs-attr">"timestamp"</span>:<span class="hljs-string">"2018-01-01T01:01:35Z"</span>,<span class="hljs-attr">"animal"</span>:<span class="hljs-string">"lion"</span>, <span class="hljs-attr">"location"</span>:<span class="hljs-number">4</span>, <span class="hljs-attr">"number"</span>:<span class="hljs-number">300</span>}
</code></pre>
<h2><a class="anchor" aria-hidden="true" id="load-data-with-transform-specs"></a><a href="#load-data-with-transform-specs" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Load data with transform specs</h2>
<p>We will ingest the sample data using the following spec, which demonstrates the use of transform specs:</p>
<pre><code class="hljs css language-json">{
  <span class="hljs-attr">"type"</span> : <span class="hljs-string">"index_parallel"</span>,
  <span class="hljs-attr">"spec"</span> : {
    <span class="hljs-attr">"dataSchema"</span> : {
      <span class="hljs-attr">"dataSource"</span> : <span class="hljs-string">"transform-tutorial"</span>,
      <span class="hljs-attr">"timestampSpec"</span>: {
        <span class="hljs-attr">"column"</span>: <span class="hljs-string">"timestamp"</span>,
        <span class="hljs-attr">"format"</span>: <span class="hljs-string">"iso"</span>
      },
      <span class="hljs-attr">"dimensionsSpec"</span> : {
        <span class="hljs-attr">"dimensions"</span> : [
          <span class="hljs-string">"animal"</span>,
          { <span class="hljs-attr">"name"</span>: <span class="hljs-string">"location"</span>, <span class="hljs-attr">"type"</span>: <span class="hljs-string">"long"</span> }
        ]
      },
      <span class="hljs-attr">"metricsSpec"</span> : [
        { <span class="hljs-attr">"type"</span> : <span class="hljs-string">"count"</span>, <span class="hljs-attr">"name"</span> : <span class="hljs-string">"count"</span> },
        { <span class="hljs-attr">"type"</span> : <span class="hljs-string">"longSum"</span>, <span class="hljs-attr">"name"</span> : <span class="hljs-string">"number"</span>, <span class="hljs-attr">"fieldName"</span> : <span class="hljs-string">"number"</span> },
        { <span class="hljs-attr">"type"</span> : <span class="hljs-string">"longSum"</span>, <span class="hljs-attr">"name"</span> : <span class="hljs-string">"triple-number"</span>, <span class="hljs-attr">"fieldName"</span> : <span class="hljs-string">"triple-number"</span> }
      ],
      <span class="hljs-attr">"granularitySpec"</span> : {
        <span class="hljs-attr">"type"</span> : <span class="hljs-string">"uniform"</span>,
        <span class="hljs-attr">"segmentGranularity"</span> : <span class="hljs-string">"week"</span>,
        <span class="hljs-attr">"queryGranularity"</span> : <span class="hljs-string">"minute"</span>,
        <span class="hljs-attr">"intervals"</span> : [<span class="hljs-string">"2018-01-01/2018-01-03"</span>],
        <span class="hljs-attr">"rollup"</span> : <span class="hljs-literal">true</span>
      },
      <span class="hljs-attr">"transformSpec"</span>: {
        <span class="hljs-attr">"transforms"</span>: [
          {
            <span class="hljs-attr">"type"</span>: <span class="hljs-string">"expression"</span>,
            <span class="hljs-attr">"name"</span>: <span class="hljs-string">"animal"</span>,
            <span class="hljs-attr">"expression"</span>: <span class="hljs-string">"concat('super-', animal)"</span>
          },
          {
            <span class="hljs-attr">"type"</span>: <span class="hljs-string">"expression"</span>,
            <span class="hljs-attr">"name"</span>: <span class="hljs-string">"triple-number"</span>,
            <span class="hljs-attr">"expression"</span>: <span class="hljs-string">"number * 3"</span>
          }
        ],
        <span class="hljs-attr">"filter"</span>: {
          <span class="hljs-attr">"type"</span>:<span class="hljs-string">"or"</span>,
          <span class="hljs-attr">"fields"</span>: [
            { <span class="hljs-attr">"type"</span>: <span class="hljs-string">"selector"</span>, <span class="hljs-attr">"dimension"</span>: <span class="hljs-string">"animal"</span>, <span class="hljs-attr">"value"</span>: <span class="hljs-string">"super-mongoose"</span> },
            { <span class="hljs-attr">"type"</span>: <span class="hljs-string">"selector"</span>, <span class="hljs-attr">"dimension"</span>: <span class="hljs-string">"triple-number"</span>, <span class="hljs-attr">"value"</span>: <span class="hljs-string">"300"</span> },
            { <span class="hljs-attr">"type"</span>: <span class="hljs-string">"selector"</span>, <span class="hljs-attr">"dimension"</span>: <span class="hljs-string">"location"</span>, <span class="hljs-attr">"value"</span>: <span class="hljs-string">"3"</span> }
          ]
        }
      }
    },
    <span class="hljs-attr">"ioConfig"</span> : {
      <span class="hljs-attr">"type"</span> : <span class="hljs-string">"index_parallel"</span>,
      <span class="hljs-attr">"inputSource"</span> : {
        <span class="hljs-attr">"type"</span> : <span class="hljs-string">"local"</span>,
        <span class="hljs-attr">"baseDir"</span> : <span class="hljs-string">"quickstart/tutorial"</span>,
        <span class="hljs-attr">"filter"</span> : <span class="hljs-string">"transform-data.json"</span>
      },
      <span class="hljs-attr">"inputFormat"</span> : {
        <span class="hljs-attr">"type"</span> :<span class="hljs-string">"json"</span>
      },
      <span class="hljs-attr">"appendToExisting"</span> : <span class="hljs-literal">false</span>
    },
    <span class="hljs-attr">"tuningConfig"</span> : {
      <span class="hljs-attr">"type"</span> : <span class="hljs-string">"index_parallel"</span>,
      <span class="hljs-attr">"partitionsSpec"</span>: {
        <span class="hljs-attr">"type"</span>: <span class="hljs-string">"dynamic"</span>
      },
      <span class="hljs-attr">"maxRowsInMemory"</span> : <span class="hljs-number">25000</span>
    }
  }
}
</code></pre>
<p>In the transform spec, we have two expression transforms:</p>
<ul>
<li><code>super-animal</code>: prepends &quot;super-&quot; to the values in the <code>animal</code> column. This will override the <code>animal</code> column with the transformed version, since the transform's name is <code>animal</code>.</li>
<li><code>triple-number</code>: multiplies the <code>number</code> column by 3. This will create a new <code>triple-number</code> column. Note that we are ingesting both the original and the transformed column.</li>
</ul>
<p>Additionally, we have an OR filter with three clauses:</p>
<ul>
<li><code>super-animal</code> values that match &quot;super-mongoose&quot;</li>
<li><code>triple-number</code> values that match 300</li>
<li><code>location</code> values that match 3</li>
</ul>
<p>This filter selects the first 3 rows, and it will exclude the final &quot;lion&quot; row in the input data. Note that the filter is applied after the transformation.</p>
<p>Let's submit this task now, which has been included at <code>quickstart/tutorial/transform-index.json</code>:</p>
<pre><code class="hljs css language-bash">bin/post-index-task --file quickstart/tutorial/transform-index.json --url http://localhost:8081
</code></pre>
<h2><a class="anchor" aria-hidden="true" id="query-the-transformed-data"></a><a href="#query-the-transformed-data" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Query the transformed data</h2>
<p>Let's run <code>bin/dsql</code> and issue a <code>select * from &quot;transform-tutorial&quot;;</code> query to see what was ingested:</p>
<pre><code class="hljs css language-bash">dsql&gt; select * from <span class="hljs-string">"transform-tutorial"</span>;
┌──────────────────────────┬────────────────┬───────┬──────────┬────────┬───────────────┐
│ __time                   │ animal         │ count │ location │ number │ triple-number │
├──────────────────────────┼────────────────┼───────┼──────────┼────────┼───────────────┤
│ 2018-01-01T05:01:00.000Z │ super-mongoose │     1 │        2 │    200 │           600 │
│ 2018-01-01T06:01:00.000Z │ super-snake    │     1 │        3 │    300 │           900 │
│ 2018-01-01T07:01:00.000Z │ super-octopus  │     1 │        1 │    100 │           300 │
└──────────────────────────┴────────────────┴───────┴──────────┴────────┴───────────────┘
Retrieved 3 rows <span class="hljs-keyword">in</span> 0.03s.
</code></pre>
<p>The &quot;lion&quot; row has been discarded, the <code>animal</code> column has been transformed, and we have both the original and transformed <code>number</code> column.</p>
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