<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Data rollup · Apache Druid</title><meta name="viewport" content="width=device-width, initial-scale=1.0"/><link rel="canonical" href="https://druid.apache.org/docs/26.0.0/ingestion/rollup.html"/><meta name="generator" content="Docusaurus"/><meta name="description" content="Introduces rollup as a concept. Provides suggestions to maximize the benefits of rollup. Differentiates between perfect and best-effort rollup."/><meta name="docsearch:language" content="en"/><meta name="docsearch:version" content="26.0.0" /><meta property="og:title" content="Data rollup · Apache Druid"/><meta property="og:type" content="website"/><meta property="og:url" content="https://druid.apache.org/index.html"/><meta property="og:description" content="Introduces rollup as a concept. Provides suggestions to maximize the benefits of rollup. Differentiates between perfect and best-effort rollup."/><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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href="/docs/26.0.0/ingestion/migrate-from-firehose.html">Migrate from firehose</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/ingestion/hadoop.html">Hadoop-based</a></li></ul></div><div class="navGroup subNavGroup"><h4 class="navGroupSubcategoryTitle">SQL-based ingestion 🆕</h4><ul><li class="navListItem"><a class="navItem" href="/docs/26.0.0/multi-stage-query/index.html">Overview</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/multi-stage-query/concepts.html">Key concepts</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/multi-stage-query/api.html">API</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/multi-stage-query/security.html">Security</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/multi-stage-query/examples.html">Examples</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/multi-stage-query/reference.html">Reference</a></li><li class="navListItem"><a 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class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/topnquery.html">TopN</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/groupbyquery.html">GroupBy</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/scan-query.html">Scan</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/searchquery.html">Search</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/timeboundaryquery.html">TimeBoundary</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/segmentmetadataquery.html">SegmentMetadata</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/datasourcemetadataquery.html">DatasourceMetadata</a></li></ul></div><div class="navGroup subNavGroup"><h4 class="navGroupSubcategoryTitle">Native query components</h4><ul><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/filters.html">Filters</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/granularities.html">Granularities</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/dimensionspecs.html">Dimensions</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/aggregations.html">Aggregations</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/post-aggregations.html">Post-aggregations</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/misc/math-expr.html">Expressions</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/having.html">Having filters (groupBy)</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/limitspec.html">Sorting and limiting (groupBy)</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/topnmetricspec.html">Sorting (topN)</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/sorting-orders.html">String comparators</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/querying/virtual-columns.html">Virtual columns</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/development/geo.html">Spatial filters</a></li></ul></div></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Configuration<span class="arrow"><svg width="24" height="24" viewBox="0 0 24 24"><path fill="#565656" d="M7.41 15.41L12 10.83l4.59 4.58L18 14l-6-6-6 6z"></path><path d="M0 0h24v24H0z" fill="none"></path></svg></span></h3><ul class="hide"><li class="navListItem"><a class="navItem" href="/docs/26.0.0/configuration/index.html">Configuration reference</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/development/extensions.html">Extensions</a></li><li class="navListItem"><a class="navItem" href="/docs/26.0.0/configuration/logging.html">Logging</a></li></ul></div><div 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<p>Druid can roll up data at ingestion time to reduce the amount of raw data to  store on disk. Rollup is a form of summarization or pre-aggregation. Rolling up data can dramatically reduce the size of data to be stored and reduce row counts by potentially orders of magnitude. As a trade-off for the efficiency of rollup, you lose the ability to query individual events.</p>
<p>At ingestion time, you control rollup with the <code>rollup</code> setting in the <a href="/docs/26.0.0/ingestion/ingestion-spec.html#granularityspec"><code>granularitySpec</code></a>. Rollup is enabled by default. This means Druid combines into a single row any rows that have identical <a href="/docs/26.0.0/ingestion/data-model.html#dimensions">dimension</a> values and <a href="/docs/26.0.0/ingestion/data-model.html#primary-timestamp">timestamp</a> values after <a href="/docs/26.0.0/ingestion/ingestion-spec.html#granularityspec"><code>queryGranularity</code>-based truncation</a>.</p>
<p>When you disable rollup, Druid loads each row as-is without doing any form of pre-aggregation. This mode is similar to databases that do not support a rollup feature. Set <code>rollup</code> to <code>false</code> if you want Druid to store each record as-is, without any rollup summarization.</p>
<p>Use roll-up when creating a table datasource if both:</p>
<ul>
<li>You want optimal performance or you have strict space constraints.</li>
<li>You don't need raw values from <a href="/docs/26.0.0/ingestion/schema-design.html#sketches">high-cardinality dimensions</a>.</li>
</ul>
<p>Conversely, disable roll-up if either:</p>
<ul>
<li>You need results for individual rows.</li>
<li>You need to execute <code>GROUP BY</code> or <code>WHERE</code> queries on <em>any</em> column.</li>
</ul>
<p>If you have conflicting needs for different use cases, you can create multiple tables with different roll-up configurations on each table.</p>
<h2><a class="anchor" aria-hidden="true" id="maximizing-rollup-ratio"></a><a href="#maximizing-rollup-ratio" 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>Maximizing rollup ratio</h2>
<p>To measure the rollup ratio of a datasource, compare the number of rows in Druid (<code>COUNT</code>) with the number of ingested events. For example, run a <a href="/docs/26.0.0/querying/sql.html">Druid SQL</a> query where &quot;num_rows&quot; refers to a <code>count</code>-type metric generated at ingestion time as follows:</p>
<pre><code class="hljs css language-sql"><span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">SUM</span>(<span class="hljs-string">"num_rows"</span>) / (<span class="hljs-keyword">COUNT</span>(*) * <span class="hljs-number">1.0</span>) <span class="hljs-keyword">FROM</span> datasource
</code></pre>
<p>The higher the result, the greater the benefit you gain from rollup. See <a href="/docs/26.0.0/ingestion/schema-design.html#counting">Counting the number of ingested events</a> for more details about how counting works with rollup is enabled.</p>
<p>Tips for maximizing rollup:</p>
<ul>
<li>Design your schema with fewer dimensions and lower cardinality dimensions to yield better rollup ratios.</li>
<li>Use <a href="/docs/26.0.0/ingestion/schema-design.html#sketches">sketches</a> to avoid storing high cardinality dimensions, which decrease rollup ratios.</li>
<li>Adjust your <code>queryGranularity</code> at ingestion time to increase the chances that multiple rows in Druid having matching timestamps. For example, use five minute query granularity (<code>PT5M</code>) instead of one minute (<code>PT1M</code>).</li>
<li>You can optionally load the same data into more than one Druid datasource. For example:
<ul>
<li>Create a &quot;full&quot; datasource that has rollup disabled, or enabled, but with a minimal rollup ratio.</li>
<li>Create a second &quot;abbreviated&quot; datasource with fewer dimensions and a higher rollup ratio.
When queries only involve dimensions in the &quot;abbreviated&quot; set, use the second datasource to reduce query times. Often, this method only requires a small increase in storage footprint because abbreviated datasources tend to be substantially smaller.</li>
</ul></li>
<li>If you use a <a href="#perfect-rollup-vs-best-effort-rollup">best-effort rollup</a> ingestion configuration that does not guarantee perfect rollup, try one of the following:
<ul>
<li>Switch to a guaranteed perfect rollup option.</li>
<li><a href="/docs/26.0.0/data-management/update.html#reindex">Reindex</a> or <a href="/docs/26.0.0/data-management/compaction.html">compact</a> your data in the background after initial ingestion.</li>
</ul></li>
</ul>
<h2><a class="anchor" aria-hidden="true" id="perfect-rollup-vs-best-effort-rollup"></a><a href="#perfect-rollup-vs-best-effort-rollup" 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>Perfect rollup vs best-effort rollup</h2>
<p>Depending on the ingestion method, Druid has the following rollup options:</p>
<ul>
<li>Guaranteed <em>perfect rollup</em>: Druid perfectly aggregates input data at ingestion time.</li>
<li><em>Best-effort rollup</em>: Druid may not perfectly aggregate input data. Therefore, multiple segments might contain rows with the same timestamp and dimension values.</li>
</ul>
<p>In general, ingestion methods that offer best-effort rollup do this for one of the following reasons:</p>
<ul>
<li>The ingestion method parallelizes ingestion without a shuffling step required for perfect rollup.</li>
<li>The ingestion method uses <em>incremental publishing</em> which means it finalizes and publishes segments before all data for a time chunk has been received.
In both of these cases, records that could theoretically be rolled up may end up in different segments. All types of streaming ingestion run in this mode.</li>
</ul>
<p>Ingestion methods that guarantee perfect rollup use an additional preprocessing step to determine intervals and partitioning before data ingestion. This preprocessing step scans the entire input dataset. While this step increases the time required for ingestion, it provides information necessary for perfect rollup.</p>
<p>The following table shows how each method handles rollup:</p>
<table>
<thead>
<tr><th>Method</th><th>How it works</th></tr>
</thead>
<tbody>
<tr><td><a href="/docs/26.0.0/ingestion/native-batch.html">Native batch</a></td><td><code>index_parallel</code> and <code>index</code> type may be either perfect or best-effort, based on configuration.</td></tr>
<tr><td><a href="/docs/26.0.0/multi-stage-query/index.html">SQL-based batch</a></td><td>Always perfect.</td></tr>
<tr><td><a href="/docs/26.0.0/ingestion/hadoop.html">Hadoop</a></td><td>Always perfect.</td></tr>
<tr><td><a href="/docs/26.0.0/development/extensions-core/kafka-ingestion.html">Kafka indexing service</a></td><td>Always best-effort.</td></tr>
<tr><td><a href="/docs/26.0.0/development/extensions-core/kinesis-ingestion.html">Kinesis indexing service</a></td><td>Always best-effort.</td></tr>
</tbody>
</table>
<h2><a class="anchor" aria-hidden="true" id="learn-more"></a><a href="#learn-more" 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>Learn more</h2>
<p>See the following topic for more information:</p>
<ul>
<li><a href="/docs/26.0.0/tutorials/tutorial-rollup.html">Rollup tutorial</a> for an example of how to configure rollup, and of how the feature modifies your data.</li>
</ul>
</span></div></article></div><div class="docs-prevnext"><a class="docs-prev button" href="/docs/26.0.0/ingestion/data-model.html"><span class="arrow-prev">← </span><span>Data model</span></a><a class="docs-next button" href="/docs/26.0.0/ingestion/partitioning.html"><span>Partitioning</span><span class="arrow-next"> →</span></a></div></div></div><nav class="onPageNav"><ul class="toc-headings"><li><a href="#maximizing-rollup-ratio">Maximizing rollup ratio</a></li><li><a href="#perfect-rollup-vs-best-effort-rollup">Perfect rollup vs best-effort rollup</a></li><li><a href="#learn-more">Learn more</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/26.0.0/">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 © 2022 <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/npm/docsearch.js@2/dist/cdn/docsearch.min.js"></script><script>
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