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| </script></nav></div><div class="container mainContainer"><div class="wrapper"><div class="post"><header class="postHeader"><a class="edit-page-link button" href="https://github.com/apache/druid/edit/master/docs/querying/query-context.md" target="_blank" rel="noreferrer noopener">Edit</a><h1 class="postHeaderTitle">Query context</h1></header><article><div><span><!-- |
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| <p>The query context is used for various query configuration parameters. The following parameters apply to all queries.</p> |
| <table> |
| <thead> |
| <tr><th>property</th><th>default</th><th>description</th></tr> |
| </thead> |
| <tbody> |
| <tr><td>timeout</td><td><code>druid.server.http.defaultQueryTimeout</code></td><td>Query timeout in millis, beyond which unfinished queries will be cancelled. 0 timeout means <code>no timeout</code>. To set the default timeout, see <a href="../configuration/index.html#broker">Broker configuration</a></td></tr> |
| <tr><td>priority</td><td><code>0</code></td><td>Query Priority. Queries with higher priority get precedence for computational resources.</td></tr> |
| <tr><td>queryId</td><td>auto-generated</td><td>Unique identifier given to this query. If a query ID is set or known, this can be used to cancel the query</td></tr> |
| <tr><td>useCache</td><td><code>true</code></td><td>Flag indicating whether to leverage the query cache for this query. When set to false, it disables reading from the query cache for this query. When set to true, Apache Druid uses <code>druid.broker.cache.useCache</code> or <code>druid.historical.cache.useCache</code> to determine whether or not to read from the query cache</td></tr> |
| <tr><td>populateCache</td><td><code>true</code></td><td>Flag indicating whether to save the results of the query to the query cache. Primarily used for debugging. When set to false, it disables saving the results of this query to the query cache. When set to true, Druid uses <code>druid.broker.cache.populateCache</code> or <code>druid.historical.cache.populateCache</code> to determine whether or not to save the results of this query to the query cache</td></tr> |
| <tr><td>useResultLevelCache</td><td><code>true</code></td><td>Flag indicating whether to leverage the result level cache for this query. When set to false, it disables reading from the query cache for this query. When set to true, Druid uses <code>druid.broker.cache.useResultLevelCache</code> to determine whether or not to read from the result-level query cache</td></tr> |
| <tr><td>populateResultLevelCache</td><td><code>true</code></td><td>Flag indicating whether to save the results of the query to the result level cache. Primarily used for debugging. When set to false, it disables saving the results of this query to the query cache. When set to true, Druid uses <code>druid.broker.cache.populateResultLevelCache</code> to determine whether or not to save the results of this query to the result-level query cache</td></tr> |
| <tr><td>bySegment</td><td><code>false</code></td><td>Return "by segment" results. Primarily used for debugging, setting it to <code>true</code> returns results associated with the data segment they came from</td></tr> |
| <tr><td>finalize</td><td><code>true</code></td><td>Flag indicating whether to "finalize" aggregation results. Primarily used for debugging. For instance, the <code>hyperUnique</code> aggregator will return the full HyperLogLog sketch instead of the estimated cardinality when this flag is set to <code>false</code></td></tr> |
| <tr><td>chunkPeriod</td><td><code>P0D</code> (off)</td><td>At the Broker process level, long interval queries (of any type) may be broken into shorter interval queries to parallelize merging more than normal. Broken up queries will use a larger share of cluster resources, but, if you use groupBy "v1, it may be able to complete faster as a result. Use ISO 8601 periods. For example, if this property is set to <code>P1M</code> (one month), then a query covering a year would be broken into 12 smaller queries. The broker uses its query processing executor service to initiate processing for query chunks, so make sure <code>druid.processing.numThreads</code> is configured appropriately on the broker. <a href="groupbyquery.html">groupBy queries</a> do not support chunkPeriod by default, although they do if using the legacy "v1" engine. This context is deprecated since it's only useful for groupBy "v1", and will be removed in the future releases.</td></tr> |
| <tr><td>maxScatterGatherBytes</td><td><code>druid.server.http.maxScatterGatherBytes</code></td><td>Maximum number of bytes gathered from data processes such as Historicals and realtime processes to execute a query. This parameter can be used to further reduce <code>maxScatterGatherBytes</code> limit at query time. See <a href="../configuration/index.html#broker">Broker configuration</a> for more details.</td></tr> |
| <tr><td>maxQueuedBytes</td><td><code>druid.broker.http.maxQueuedBytes</code></td><td>Maximum number of bytes queued per query before exerting backpressure on the channel to the data server. Similar to <code>maxScatterGatherBytes</code>, except unlike that configuration, this one will trigger backpressure rather than query failure. Zero means disabled.</td></tr> |
| <tr><td>serializeDateTimeAsLong</td><td><code>false</code></td><td>If true, DateTime is serialized as long in the result returned by Broker and the data transportation between Broker and compute process</td></tr> |
| <tr><td>serializeDateTimeAsLongInner</td><td><code>false</code></td><td>If true, DateTime is serialized as long in the data transportation between Broker and compute process</td></tr> |
| <tr><td>enableParallelMerge</td><td><code>true</code></td><td>Enable parallel result merging on the Broker. Note that <code>druid.processing.merge.useParallelMergePool</code> must be enabled for this setting to be set to <code>true</code>. See <a href="../configuration/index.html#broker">Broker configuration</a> for more details.</td></tr> |
| <tr><td>parallelMergeParallelism</td><td><code>druid.processing.merge.pool.parallelism</code></td><td>Maximum number of parallel threads to use for parallel result merging on the Broker. See <a href="../configuration/index.html#broker">Broker configuration</a> for more details.</td></tr> |
| <tr><td>parallelMergeInitialYieldRows</td><td><code>druid.processing.merge.task.initialYieldNumRows</code></td><td>Number of rows to yield per ForkJoinPool merge task for parallel result merging on the Broker, before forking off a new task to continue merging sequences. See <a href="../configuration/index.html#broker">Broker configuration</a> for more details.</td></tr> |
| <tr><td>parallelMergeSmallBatchRows</td><td><code>druid.processing.merge.task.smallBatchNumRows</code></td><td>Size of result batches to operate on in ForkJoinPool merge tasks for parallel result merging on the Broker. See <a href="../configuration/index.html#broker">Broker configuration</a> for more details.</td></tr> |
| </tbody> |
| </table> |
| <p>In addition, some query types offer context parameters specific to that query type.</p> |
| <h3><a class="anchor" aria-hidden="true" id="topn-queries"></a><a href="#topn-queries" 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>TopN queries</h3> |
| <table> |
| <thead> |
| <tr><th>property</th><th>default</th><th>description</th></tr> |
| </thead> |
| <tbody> |
| <tr><td>minTopNThreshold</td><td><code>1000</code></td><td>The top minTopNThreshold local results from each segment are returned for merging to determine the global topN.</td></tr> |
| </tbody> |
| </table> |
| <h3><a class="anchor" aria-hidden="true" id="timeseries-queries"></a><a href="#timeseries-queries" 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>Timeseries queries</h3> |
| <table> |
| <thead> |
| <tr><th>property</th><th>default</th><th>description</th></tr> |
| </thead> |
| <tbody> |
| <tr><td>skipEmptyBuckets</td><td><code>false</code></td><td>Disable timeseries zero-filling behavior, so only buckets with results will be returned.</td></tr> |
| </tbody> |
| </table> |
| <h3><a class="anchor" aria-hidden="true" id="groupby-queries"></a><a href="#groupby-queries" 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>GroupBy queries</h3> |
| <p>See <a href="/docs/0.17.1/querying/groupbyquery.html#advanced-configurations">GroupBy query context</a>.</p> |
| <h3><a class="anchor" aria-hidden="true" id="vectorizable-queries"></a><a href="#vectorizable-queries" 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>Vectorizable queries</h3> |
| <p>The GroupBy and Timeseries query types can run in <em>vectorized</em> mode, which speeds up query execution by processing |
| batches of rows at a time. Not all queries can be vectorized. In particular, vectorization currently has the following |
| requirements:</p> |
| <ul> |
| <li>All query-level filters must either be able to run on bitmap indexes or must offer vectorized row-matchers. These |
| include "selector", "bound", "in", "like", "regex", "search", "and", "or", and "not".</li> |
| <li>All filters in filtered aggregators must offer vectorized row-matchers.</li> |
| <li>All aggregators must offer vectorized implementations. These include "count", "doubleSum", "floatSum", "longSum", |
| "hyperUnique", and "filtered".</li> |
| <li>No virtual columns.</li> |
| <li>For GroupBy: All dimension specs must be "default" (no extraction functions or filtered dimension specs).</li> |
| <li>For GroupBy: No multi-value dimensions.</li> |
| <li>For Timeseries: No "descending" order.</li> |
| <li>Only immutable segments (not real-time).</li> |
| </ul> |
| <p>Other query types (like TopN, Scan, Select, and Search) ignore the "vectorize" parameter, and will execute without |
| vectorization. These query types will ignore the "vectorize" parameter even if it is set to <code>"force"</code>.</p> |
| <p>Vectorization is an alpha-quality feature as of Druid 0.17.1. We heartily welcome any feedback and testing |
| from the community as we work to battle-test it.</p> |
| <table> |
| <thead> |
| <tr><th>property</th><th>default</th><th>description</th></tr> |
| </thead> |
| <tbody> |
| <tr><td>vectorize</td><td><code>false</code></td><td>Enables or disables vectorized query execution. Possible values are <code>false</code> (disabled), <code>true</code> (enabled if possible, disabled otherwise, on a per-segment basis), and <code>force</code> (enabled, and groupBy or timeseries queries that cannot be vectorized will fail). The <code>"force"</code> setting is meant to aid in testing, and is not generally useful in production (since real-time segments can never be processed with vectorized execution, any queries on real-time data will fail). This will override <code>druid.query.vectorize</code> if it's set.</td></tr> |
| <tr><td>vectorSize</td><td><code>512</code></td><td>Sets the row batching size for a particular query. This will override <code>druid.query.vectorSize</code> if it's set.</td></tr> |
| </tbody> |
| </table> |
| </span></div></article></div><div class="docs-prevnext"><a class="docs-prev button" href="/docs/0.17.1/querying/post-aggregations.html"><span class="arrow-prev">← </span><span>Post-Aggregations</span></a><a class="docs-next button" href="/docs/0.17.1/querying/searchqueryspec.html"><span>Refining search queries</span><span class="arrow-next"> →</span></a></div></div></div><nav class="onPageNav"></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/0.17.1/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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