<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Tutorial: Compacting segments · Apache Druid</title><meta name="viewport" content="width=device-width"/><link rel="canonical" href="https://druid.apache.org/docs/0.18.0/tutorials/tutorial-compaction.html"/><meta name="generator" content="Docusaurus"/><meta name="description" content="&lt;!--"/><meta name="docsearch:language" content="en"/><meta name="docsearch:version" content="0.18.0" /><meta property="og:title" content="Tutorial: Compacting segments · 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/docsearch.js/1/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 demonstrates how to compact existing segments into fewer but larger segments.</p>
<p>Because there is some per-segment memory and processing overhead, it can sometimes be beneficial to reduce the total number of segments.
Please check <a href="/docs/0.18.0/operations/segment-optimization.html">Segment size optimization</a> for details.</p>
<p>For this tutorial, we'll assume you've already downloaded Apache Druid as described in
the <a href="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/0.18.0/tutorials/tutorial-batch.html">Tutorial: Loading a file</a> and <a href="/docs/0.18.0/tutorials/tutorial-query.html">Tutorial: Querying data</a>.</p>
<h2><a class="anchor" aria-hidden="true" id="load-the-initial-data"></a><a href="#load-the-initial-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>Load the initial data</h2>
<p>For this tutorial, we'll be using the Wikipedia edits sample data, with an ingestion task spec that will create 1-3 segments per hour in the input data.</p>
<p>The ingestion spec can be found at <code>quickstart/tutorial/compaction-init-index.json</code>. Let's submit that spec, which will create a datasource called <code>compaction-tutorial</code>:</p>
<pre><code class="hljs css language-bash">bin/post-index-task --file quickstart/tutorial/compaction-init-index.json --url http://localhost:8081
</code></pre>
<blockquote>
<p>Please note that <code>maxRowsPerSegment</code> in the ingestion spec is set to 1000. This is to generate multiple segments per hour and <em>NOT</em> recommended in production.
It's 5000000 by default and may need to be adjusted to make your segments optimized.</p>
</blockquote>
<p>After the ingestion completes, go to <a href="http://localhost:8888/unified-console.html#datasources">http://localhost:8888/unified-console.html#datasources</a> in a browser to see the new datasource in the Druid Console.</p>
<p><img src="../assets/tutorial-compaction-01.png" alt="compaction-tutorial datasource" title="compaction-tutorial datasource"></p>
<p>Click the <code>51 segments</code> link next to &quot;Fully Available&quot; for the <code>compaction-tutorial</code> datasource to view information about the datasource's segments:</p>
<p>There will be 51 segments for this datasource, 1-3 segments per hour in the input data:</p>
<p><img src="../assets/tutorial-compaction-02.png" alt="Original segments" title="Original segments"></p>
<p>Running a COUNT(*) query on this datasource shows that there are 39,244 rows:</p>
<pre><code class="hljs css language-bash">dsql&gt; select count(*) from <span class="hljs-string">"compaction-tutorial"</span>;
┌────────┐
│ EXPR<span class="hljs-variable">$0</span> │
├────────┤
│  39244 │
└────────┘
Retrieved 1 row <span class="hljs-keyword">in</span> 1.38s.
</code></pre>
<h2><a class="anchor" aria-hidden="true" id="compact-the-data"></a><a href="#compact-the-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>Compact the data</h2>
<p>Let's now compact these 51 small segments.</p>
<p>We have included a compaction task spec for this tutorial datasource at <code>quickstart/tutorial/compaction-keep-granularity.json</code>:</p>
<pre><code class="hljs css language-json">{
  <span class="hljs-attr">"type"</span>: <span class="hljs-string">"compact"</span>,
  <span class="hljs-attr">"dataSource"</span>: <span class="hljs-string">"compaction-tutorial"</span>,
  <span class="hljs-attr">"interval"</span>: <span class="hljs-string">"2015-09-12/2015-09-13"</span>,
  <span class="hljs-attr">"tuningConfig"</span> : {
    <span class="hljs-attr">"type"</span> : <span class="hljs-string">"index_parallel"</span>,
    <span class="hljs-attr">"maxRowsPerSegment"</span> : <span class="hljs-number">5000000</span>,
    <span class="hljs-attr">"maxRowsInMemory"</span> : <span class="hljs-number">25000</span>
  }
}
</code></pre>
<p>This will compact all segments for the interval <code>2015-09-12/2015-09-13</code> in the <code>compaction-tutorial</code> datasource.</p>
<p>The parameters in the <code>tuningConfig</code> control how many segments will be present in the compacted set of segments.</p>
<p>In this tutorial example, only one compacted segment will be created per hour, as each hour has less rows than the 5000000 <code>maxRowsPerSegment</code> (note that the total number of rows is 39244).</p>
<p>Let's submit this task now:</p>
<pre><code class="hljs css language-bash">bin/post-index-task --file quickstart/tutorial/compaction-keep-granularity.json --url http://localhost:8081
</code></pre>
<p>After the task finishes, refresh the <a href="http://localhost:8888/unified-console.html#segments">segments view</a>.</p>
<p>The original 51 segments will eventually be marked as &quot;unused&quot; by the Coordinator and removed, with the new compacted segments remaining.</p>
<p>By default, the Druid Coordinator will not mark segments as unused until the Coordinator process has been up for at least 15 minutes, so you may see the old segment set and the new compacted set at the same time in the Druid Console, with 75 total segments:</p>
<p><img src="../assets/tutorial-compaction-03.png" alt="Compacted segments intermediate state 1" title="Compacted segments intermediate state 1"></p>
<p><img src="../assets/tutorial-compaction-04.png" alt="Compacted segments intermediate state 2" title="Compacted segments intermediate state 2"></p>
<p>The new compacted segments have a more recent version than the original segments, so even when both sets of segments are shown in the Druid Console, queries will only read from the new compacted segments.</p>
<p>Let's try running a COUNT(*) on <code>compaction-tutorial</code> again, where the row count should still be 39,244:</p>
<pre><code class="hljs css language-bash">dsql&gt; select count(*) from <span class="hljs-string">"compaction-tutorial"</span>;
┌────────┐
│ EXPR<span class="hljs-variable">$0</span> │
├────────┤
│  39244 │
└────────┘
Retrieved 1 row <span class="hljs-keyword">in</span> 1.30s.
</code></pre>
<p>After the Coordinator has been running for at least 15 minutes, the <a href="http://localhost:8888/unified-console.html#segments">segments view</a> should show there are 24 segments, one per hour:</p>
<p><img src="../assets/tutorial-compaction-05.png" alt="Compacted segments hourly granularity 1" title="Compacted segments hourly granularity 1"></p>
<p><img src="../assets/tutorial-compaction-06.png" alt="Compacted segments hourly granularity 2" title="Compacted segments hourly granularity 2"></p>
<h2><a class="anchor" aria-hidden="true" id="compact-the-data-with-new-segment-granularity"></a><a href="#compact-the-data-with-new-segment-granularity" 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>Compact the data with new segment granularity</h2>
<p>The compaction task can also produce compacted segments with a granularity different from the granularity of the input segments.</p>
<p>We have included a compaction task spec that will create DAY granularity segments at <code>quickstart/tutorial/compaction-day-granularity.json</code>:</p>
<pre><code class="hljs css language-json">{
  <span class="hljs-attr">"type"</span>: <span class="hljs-string">"compact"</span>,
  <span class="hljs-attr">"dataSource"</span>: <span class="hljs-string">"compaction-tutorial"</span>,
  <span class="hljs-attr">"interval"</span>: <span class="hljs-string">"2015-09-12/2015-09-13"</span>,
  <span class="hljs-attr">"segmentGranularity"</span>: <span class="hljs-string">"DAY"</span>,
  <span class="hljs-attr">"tuningConfig"</span> : {
    <span class="hljs-attr">"type"</span> : <span class="hljs-string">"index_parallel"</span>,
    <span class="hljs-attr">"maxRowsPerSegment"</span> : <span class="hljs-number">5000000</span>,
    <span class="hljs-attr">"maxRowsInMemory"</span> : <span class="hljs-number">25000</span>,
    <span class="hljs-attr">"forceExtendableShardSpecs"</span> : <span class="hljs-literal">true</span>
  }
}
</code></pre>
<p>Note that <code>segmentGranularity</code> is set to <code>DAY</code> in this compaction task spec.</p>
<p>Let's submit this task now:</p>
<pre><code class="hljs css language-bash">bin/post-index-task --file quickstart/tutorial/compaction-day-granularity.json --url http://localhost:8081
</code></pre>
<p>It will take a bit of time before the Coordinator marks the old input segments as unused, so you may see an intermediate state with 25 total segments. Eventually, there will only be one DAY granularity segment:</p>
<p><img src="../assets/tutorial-compaction-07.png" alt="Compacted segments day granularity 1" title="Compacted segments day granularity 1"></p>
<p><img src="../assets/tutorial-compaction-08.png" alt="Compacted segments day granularity 2" title="Compacted segments day granularity 2"></p>
<h2><a class="anchor" aria-hidden="true" id="further-reading"></a><a href="#further-reading" 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>Further reading</h2>
<p><a href="/docs/0.18.0/ingestion/tasks.html">Task documentation</a></p>
<p><a href="/docs/0.18.0/operations/segment-optimization.html">Segment optimization</a></p>
</span></div></article></div><div class="docs-prevnext"><a class="docs-prev button" href="/docs/0.18.0/tutorials/tutorial-update-data.html"><span class="arrow-prev">← </span><span>Updating existing data</span></a><a class="docs-next button" href="/docs/0.18.0/tutorials/tutorial-delete-data.html"><span>Deleting data</span><span class="arrow-next"> →</span></a></div></div></div><nav class="onPageNav"><ul class="toc-headings"><li><a href="#load-the-initial-data">Load the initial data</a></li><li><a href="#compact-the-data">Compact the data</a></li><li><a href="#compact-the-data-with-new-segment-granularity">Compact the data with new segment granularity</a></li><li><a href="#further-reading">Further reading</a></li></ul></nav></div><footer class="nav-footer druid-footer" id="footer"><div class="container"><div class="text-center"><p><a href="/technology">Technology</a> · <a href="/use-cases">Use Cases</a> · <a href="/druid-powered">Powered by Druid</a> · <a href="/docs/0.18.0/latest">Docs</a> · <a href="/community/">Community</a> · <a href="/downloads.html">Download</a> · <a href="/faq">FAQ</a></p></div><div class="text-center"><a title="Join the user group" href="https://groups.google.com/forum/#!forum/druid-user" target="_blank"><span class="fa fa-comments"></span></a> · <a title="Follow Druid" href="https://twitter.com/druidio" target="_blank"><span class="fab fa-twitter"></span></a> · <a title="Download via Apache" href="https://www.apache.org/dyn/closer.cgi?path=/incubator/druid/{{ site.druid_versions[0].versions[0].version }}/apache-druid-{{ site.druid_versions[0].versions[0].version }}-bin.tar.gz" target="_blank"><span class="fas fa-feather"></span></a> · <a title="GitHub" href="https://github.com/apache/druid" target="_blank"><span class="fab fa-github"></span></a></div><div class="text-center license">Copyright © 2019 <a href="https://www.apache.org/" target="_blank">Apache Software Foundation</a>.<br/>Except where otherwise noted, licensed under <a rel="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA 4.0</a>.<br/>Apache Druid, Druid, and the Druid logo are either registered trademarks or trademarks of The Apache Software Foundation in the United States and other countries.</div></div></footer></div><script type="text/javascript" src="https://cdn.jsdelivr.net/docsearch.js/1/docsearch.min.js"></script><script>
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