| <!DOCTYPE html> |
| <html lang="en"> |
| <head> |
| <meta charset="UTF-8" /> |
| <meta name="viewport" content="width=device-width, initial-scale=1.0"> |
| <meta name="description" content="Apache Druid"> |
| <meta name="keywords" content="druid,kafka,database,analytics,streaming,real-time,real time,apache,open source"> |
| <meta name="author" content="Apache Software Foundation"> |
| |
| <title>Druid | Scan query</title> |
| |
| <link rel="alternate" type="application/atom+xml" href="/feed"> |
| <link rel="shortcut icon" href="/img/favicon.png"> |
| |
| <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.7.2/css/all.css" integrity="sha384-fnmOCqbTlWIlj8LyTjo7mOUStjsKC4pOpQbqyi7RrhN7udi9RwhKkMHpvLbHG9Sr" crossorigin="anonymous"> |
| |
| <link href='//fonts.googleapis.com/css?family=Open+Sans+Condensed:300,700,300italic|Open+Sans:300italic,400italic,600italic,400,300,600,700' rel='stylesheet' type='text/css'> |
| |
| <link rel="stylesheet" href="/css/bootstrap-pure.css?v=1.1"> |
| <link rel="stylesheet" href="/css/base.css?v=1.1"> |
| <link rel="stylesheet" href="/css/header.css?v=1.1"> |
| <link rel="stylesheet" href="/css/footer.css?v=1.1"> |
| <link rel="stylesheet" href="/css/syntax.css?v=1.1"> |
| <link rel="stylesheet" href="/css/docs.css?v=1.1"> |
| |
| <script> |
| (function() { |
| var cx = '000162378814775985090:molvbm0vggm'; |
| var gcse = document.createElement('script'); |
| gcse.type = 'text/javascript'; |
| gcse.async = true; |
| gcse.src = (document.location.protocol == 'https:' ? 'https:' : 'http:') + |
| '//cse.google.com/cse.js?cx=' + cx; |
| var s = document.getElementsByTagName('script')[0]; |
| s.parentNode.insertBefore(gcse, s); |
| })(); |
| </script> |
| |
| |
| </head> |
| |
| <body> |
| <!-- Start page_header include --> |
| <script src="//ajax.googleapis.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script> |
| |
| <div class="top-navigator"> |
| <div class="container"> |
| <div class="left-cont"> |
| <a class="logo" href="/"><span class="druid-logo"></span></a> |
| </div> |
| <div class="right-cont"> |
| <ul class="links"> |
| <li class=""><a href="/technology">Technology</a></li> |
| <li class=""><a href="/use-cases">Use Cases</a></li> |
| <li class=""><a href="/druid-powered">Powered By</a></li> |
| <li class=""><a href="/docs/latest/design/">Docs</a></li> |
| <li class=""><a href="/community/">Community</a></li> |
| <li class="header-dropdown"> |
| <a>Apache</a> |
| <div class="header-dropdown-menu"> |
| <a href="https://www.apache.org/" target="_blank">Foundation</a> |
| <a href="https://www.apache.org/events/current-event" target="_blank">Events</a> |
| <a href="https://www.apache.org/licenses/" target="_blank">License</a> |
| <a href="https://www.apache.org/foundation/thanks.html" target="_blank">Thanks</a> |
| <a href="https://www.apache.org/security/" target="_blank">Security</a> |
| <a href="https://www.apache.org/foundation/sponsorship.html" target="_blank">Sponsorship</a> |
| </div> |
| </li> |
| <li class=" button-link"><a href="/downloads.html">Download</a></li> |
| </ul> |
| </div> |
| </div> |
| <div class="action-button menu-icon"> |
| <span class="fa fa-bars"></span> MENU |
| </div> |
| <div class="action-button menu-icon-close"> |
| <span class="fa fa-times"></span> MENU |
| </div> |
| </div> |
| |
| <script type="text/javascript"> |
| var $menu = $('.right-cont'); |
| var $menuIcon = $('.menu-icon'); |
| var $menuIconClose = $('.menu-icon-close'); |
| |
| function showMenu() { |
| $menu.fadeIn(100); |
| $menuIcon.fadeOut(100); |
| $menuIconClose.fadeIn(100); |
| } |
| |
| $menuIcon.click(showMenu); |
| |
| function hideMenu() { |
| $menu.fadeOut(100); |
| $menuIconClose.fadeOut(100); |
| $menuIcon.fadeIn(100); |
| } |
| |
| $menuIconClose.click(hideMenu); |
| |
| $(window).resize(function() { |
| if ($(window).width() >= 840) { |
| $menu.fadeIn(100); |
| $menuIcon.fadeOut(100); |
| $menuIconClose.fadeOut(100); |
| } |
| else { |
| $menu.fadeOut(100); |
| $menuIcon.fadeIn(100); |
| $menuIconClose.fadeOut(100); |
| } |
| }); |
| </script> |
| |
| <!-- Stop page_header include --> |
| |
| |
| <div class="container doc-container"> |
| |
| |
| |
| |
| <p> Looking for the <a href="/docs/0.20.0/">latest stable documentation</a>?</p> |
| |
| |
| <div class="row"> |
| <div class="col-md-9 doc-content"> |
| <p> |
| <a class="btn btn-default btn-xs visible-xs-inline-block visible-sm-inline-block" href="#toc">Table of Contents</a> |
| </p> |
| <!-- |
| ~ Licensed to the Apache Software Foundation (ASF) under one |
| ~ or more contributor license agreements. See the NOTICE file |
| ~ distributed with this work for additional information |
| ~ regarding copyright ownership. The ASF licenses this file |
| ~ to you under the Apache License, Version 2.0 (the |
| ~ "License"); you may not use this file except in compliance |
| ~ with the License. You may obtain a copy of the License at |
| ~ |
| ~ http://www.apache.org/licenses/LICENSE-2.0 |
| ~ |
| ~ Unless required by applicable law or agreed to in writing, |
| ~ software distributed under the License is distributed on an |
| ~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| ~ KIND, either express or implied. See the License for the |
| ~ specific language governing permissions and limitations |
| ~ under the License. |
| --> |
| |
| <h1 id="scan-query">Scan query</h1> |
| |
| <p>The Scan query returns raw Apache Druid (incubating) rows in streaming mode. The biggest difference between the Select query and the Scan |
| query is that the Scan query does not retain all the returned rows in memory before they are returned to the client.<br> |
| The Select query <em>will</em> retain the rows in memory, causing memory pressure if too many rows are returned.<br> |
| The Scan query can return all the rows without issuing another pagination query.</p> |
| |
| <p>In addition to straightforward usage where a Scan query is issued to the Broker, the Scan query can also be issued |
| directly to Historical processes or streaming ingestion tasks. This can be useful if you want to retrieve large |
| amounts of data in parallel.</p> |
| |
| <p>An example Scan query object is shown below:</p> |
| <div class="highlight"><pre><code class="language-json" data-lang="json"><span></span> <span class="p">{</span> |
| <span class="nt">"queryType"</span><span class="p">:</span> <span class="s2">"scan"</span><span class="p">,</span> |
| <span class="nt">"dataSource"</span><span class="p">:</span> <span class="s2">"wikipedia"</span><span class="p">,</span> |
| <span class="nt">"resultFormat"</span><span class="p">:</span> <span class="s2">"list"</span><span class="p">,</span> |
| <span class="nt">"columns"</span><span class="p">:[],</span> |
| <span class="nt">"intervals"</span><span class="p">:</span> <span class="p">[</span> |
| <span class="s2">"2013-01-01/2013-01-02"</span> |
| <span class="p">],</span> |
| <span class="nt">"batchSize"</span><span class="p">:</span><span class="mi">20480</span><span class="p">,</span> |
| <span class="nt">"limit"</span><span class="p">:</span><span class="mi">3</span> |
| <span class="p">}</span> |
| </code></pre></div> |
| <p>The following are the main parameters for Scan queries:</p> |
| |
| <table><thead> |
| <tr> |
| <th>property</th> |
| <th>description</th> |
| <th>required?</th> |
| </tr> |
| </thead><tbody> |
| <tr> |
| <td>queryType</td> |
| <td>This String should always be "scan"; this is the first thing Druid looks at to figure out how to interpret the query</td> |
| <td>yes</td> |
| </tr> |
| <tr> |
| <td>dataSource</td> |
| <td>A String or Object defining the data source to query, very similar to a table in a relational database. See <a href="../querying/datasource.html">DataSource</a> for more information.</td> |
| <td>yes</td> |
| </tr> |
| <tr> |
| <td>intervals</td> |
| <td>A JSON Object representing ISO-8601 Intervals. This defines the time ranges to run the query over.</td> |
| <td>yes</td> |
| </tr> |
| <tr> |
| <td>resultFormat</td> |
| <td>How the results are represented: list, compactedList or valueVector. Currently only <code>list</code> and <code>compactedList</code> are supported. Default is <code>list</code></td> |
| <td>no</td> |
| </tr> |
| <tr> |
| <td>filter</td> |
| <td>See <a href="../querying/filters.html">Filters</a></td> |
| <td>no</td> |
| </tr> |
| <tr> |
| <td>columns</td> |
| <td>A String array of dimensions and metrics to scan. If left empty, all dimensions and metrics are returned.</td> |
| <td>no</td> |
| </tr> |
| <tr> |
| <td>batchSize</td> |
| <td>How many rows buffered before return to client. Default is <code>20480</code></td> |
| <td>no</td> |
| </tr> |
| <tr> |
| <td>limit</td> |
| <td>How many rows to return. If not specified, all rows will be returned.</td> |
| <td>no</td> |
| </tr> |
| <tr> |
| <td>order</td> |
| <td>The ordering of returned rows based on timestamp. "ascending", "descending", and "none" (default) are supported. Currently, "ascending" and "descending" are only supported for queries where the <code>__time</code> column is included in the <code>columns</code> field and the requirements outlined in the <a href="#time-ordering">time ordering</a> section are met.</td> |
| <td>none</td> |
| </tr> |
| <tr> |
| <td>legacy</td> |
| <td>Return results consistent with the legacy "scan-query" contrib extension. Defaults to the value set by <code>druid.query.scan.legacy</code>, which in turn defaults to false. See <a href="#legacy-mode">Legacy mode</a> for details.</td> |
| <td>no</td> |
| </tr> |
| <tr> |
| <td>context</td> |
| <td>An additional JSON Object which can be used to specify certain flags (see the Query Context Properties section below).</td> |
| <td>no</td> |
| </tr> |
| </tbody></table> |
| |
| <h2 id="example-results">Example results</h2> |
| |
| <p>The format of the result when resultFormat equals <code>list</code>:</p> |
| <div class="highlight"><pre><code class="language-json" data-lang="json"><span></span> <span class="p">[{</span> |
| <span class="nt">"segmentId"</span> <span class="p">:</span> <span class="s2">"wikipedia_editstream_2012-12-29T00:00:00.000Z_2013-01-10T08:00:00.000Z_2013-01-10T08:13:47.830Z_v9"</span><span class="p">,</span> |
| <span class="nt">"columns"</span> <span class="p">:</span> <span class="p">[</span> |
| <span class="s2">"timestamp"</span><span class="p">,</span> |
| <span class="s2">"robot"</span><span class="p">,</span> |
| <span class="s2">"namespace"</span><span class="p">,</span> |
| <span class="s2">"anonymous"</span><span class="p">,</span> |
| <span class="s2">"unpatrolled"</span><span class="p">,</span> |
| <span class="s2">"page"</span><span class="p">,</span> |
| <span class="s2">"language"</span><span class="p">,</span> |
| <span class="s2">"newpage"</span><span class="p">,</span> |
| <span class="s2">"user"</span><span class="p">,</span> |
| <span class="s2">"count"</span><span class="p">,</span> |
| <span class="s2">"added"</span><span class="p">,</span> |
| <span class="s2">"delta"</span><span class="p">,</span> |
| <span class="s2">"variation"</span><span class="p">,</span> |
| <span class="s2">"deleted"</span> |
| <span class="p">],</span> |
| <span class="nt">"events"</span> <span class="p">:</span> <span class="p">[</span> <span class="p">{</span> |
| <span class="nt">"timestamp"</span> <span class="p">:</span> <span class="s2">"2013-01-01T00:00:00.000Z"</span><span class="p">,</span> |
| <span class="nt">"robot"</span> <span class="p">:</span> <span class="s2">"1"</span><span class="p">,</span> |
| <span class="nt">"namespace"</span> <span class="p">:</span> <span class="s2">"article"</span><span class="p">,</span> |
| <span class="nt">"anonymous"</span> <span class="p">:</span> <span class="s2">"0"</span><span class="p">,</span> |
| <span class="nt">"unpatrolled"</span> <span class="p">:</span> <span class="s2">"0"</span><span class="p">,</span> |
| <span class="nt">"page"</span> <span class="p">:</span> <span class="s2">"11._korpus_(NOVJ)"</span><span class="p">,</span> |
| <span class="nt">"language"</span> <span class="p">:</span> <span class="s2">"sl"</span><span class="p">,</span> |
| <span class="nt">"newpage"</span> <span class="p">:</span> <span class="s2">"0"</span><span class="p">,</span> |
| <span class="nt">"user"</span> <span class="p">:</span> <span class="s2">"EmausBot"</span><span class="p">,</span> |
| <span class="nt">"count"</span> <span class="p">:</span> <span class="mf">1.0</span><span class="p">,</span> |
| <span class="nt">"added"</span> <span class="p">:</span> <span class="mf">39.0</span><span class="p">,</span> |
| <span class="nt">"delta"</span> <span class="p">:</span> <span class="mf">39.0</span><span class="p">,</span> |
| <span class="nt">"variation"</span> <span class="p">:</span> <span class="mf">39.0</span><span class="p">,</span> |
| <span class="nt">"deleted"</span> <span class="p">:</span> <span class="mf">0.0</span> |
| <span class="p">},</span> <span class="p">{</span> |
| <span class="nt">"timestamp"</span> <span class="p">:</span> <span class="s2">"2013-01-01T00:00:00.000Z"</span><span class="p">,</span> |
| <span class="nt">"robot"</span> <span class="p">:</span> <span class="s2">"0"</span><span class="p">,</span> |
| <span class="nt">"namespace"</span> <span class="p">:</span> <span class="s2">"article"</span><span class="p">,</span> |
| <span class="nt">"anonymous"</span> <span class="p">:</span> <span class="s2">"0"</span><span class="p">,</span> |
| <span class="nt">"unpatrolled"</span> <span class="p">:</span> <span class="s2">"0"</span><span class="p">,</span> |
| <span class="nt">"page"</span> <span class="p">:</span> <span class="s2">"112_U.S._580"</span><span class="p">,</span> |
| <span class="nt">"language"</span> <span class="p">:</span> <span class="s2">"en"</span><span class="p">,</span> |
| <span class="nt">"newpage"</span> <span class="p">:</span> <span class="s2">"1"</span><span class="p">,</span> |
| <span class="nt">"user"</span> <span class="p">:</span> <span class="s2">"MZMcBride"</span><span class="p">,</span> |
| <span class="nt">"count"</span> <span class="p">:</span> <span class="mf">1.0</span><span class="p">,</span> |
| <span class="nt">"added"</span> <span class="p">:</span> <span class="mf">70.0</span><span class="p">,</span> |
| <span class="nt">"delta"</span> <span class="p">:</span> <span class="mf">70.0</span><span class="p">,</span> |
| <span class="nt">"variation"</span> <span class="p">:</span> <span class="mf">70.0</span><span class="p">,</span> |
| <span class="nt">"deleted"</span> <span class="p">:</span> <span class="mf">0.0</span> |
| <span class="p">},</span> <span class="p">{</span> |
| <span class="nt">"timestamp"</span> <span class="p">:</span> <span class="s2">"2013-01-01T00:00:00.000Z"</span><span class="p">,</span> |
| <span class="nt">"robot"</span> <span class="p">:</span> <span class="s2">"0"</span><span class="p">,</span> |
| <span class="nt">"namespace"</span> <span class="p">:</span> <span class="s2">"article"</span><span class="p">,</span> |
| <span class="nt">"anonymous"</span> <span class="p">:</span> <span class="s2">"0"</span><span class="p">,</span> |
| <span class="nt">"unpatrolled"</span> <span class="p">:</span> <span class="s2">"0"</span><span class="p">,</span> |
| <span class="nt">"page"</span> <span class="p">:</span> <span class="s2">"113_U.S._243"</span><span class="p">,</span> |
| <span class="nt">"language"</span> <span class="p">:</span> <span class="s2">"en"</span><span class="p">,</span> |
| <span class="nt">"newpage"</span> <span class="p">:</span> <span class="s2">"1"</span><span class="p">,</span> |
| <span class="nt">"user"</span> <span class="p">:</span> <span class="s2">"MZMcBride"</span><span class="p">,</span> |
| <span class="nt">"count"</span> <span class="p">:</span> <span class="mf">1.0</span><span class="p">,</span> |
| <span class="nt">"added"</span> <span class="p">:</span> <span class="mf">77.0</span><span class="p">,</span> |
| <span class="nt">"delta"</span> <span class="p">:</span> <span class="mf">77.0</span><span class="p">,</span> |
| <span class="nt">"variation"</span> <span class="p">:</span> <span class="mf">77.0</span><span class="p">,</span> |
| <span class="nt">"deleted"</span> <span class="p">:</span> <span class="mf">0.0</span> |
| <span class="p">}</span> <span class="p">]</span> |
| <span class="p">}</span> <span class="p">]</span> |
| </code></pre></div> |
| <p>The format of the result when resultFormat equals <code>compactedList</code>:</p> |
| <div class="highlight"><pre><code class="language-json" data-lang="json"><span></span> <span class="p">[{</span> |
| <span class="nt">"segmentId"</span> <span class="p">:</span> <span class="s2">"wikipedia_editstream_2012-12-29T00:00:00.000Z_2013-01-10T08:00:00.000Z_2013-01-10T08:13:47.830Z_v9"</span><span class="p">,</span> |
| <span class="nt">"columns"</span> <span class="p">:</span> <span class="p">[</span> |
| <span class="s2">"timestamp"</span><span class="p">,</span> <span class="s2">"robot"</span><span class="p">,</span> <span class="s2">"namespace"</span><span class="p">,</span> <span class="s2">"anonymous"</span><span class="p">,</span> <span class="s2">"unpatrolled"</span><span class="p">,</span> <span class="s2">"page"</span><span class="p">,</span> <span class="s2">"language"</span><span class="p">,</span> <span class="s2">"newpage"</span><span class="p">,</span> <span class="s2">"user"</span><span class="p">,</span> <span class="s2">"count"</span><span class="p">,</span> <span class="s2">"added"</span><span class="p">,</span> <span class="s2">"delta"</span><span class="p">,</span> <span class="s2">"variation"</span><span class="p">,</span> <span class="s2">"deleted"</span> |
| <span class="p">],</span> |
| <span class="nt">"events"</span> <span class="p">:</span> <span class="p">[</span> |
| <span class="p">[</span><span class="s2">"2013-01-01T00:00:00.000Z"</span><span class="p">,</span> <span class="s2">"1"</span><span class="p">,</span> <span class="s2">"article"</span><span class="p">,</span> <span class="s2">"0"</span><span class="p">,</span> <span class="s2">"0"</span><span class="p">,</span> <span class="s2">"11._korpus_(NOVJ)"</span><span class="p">,</span> <span class="s2">"sl"</span><span class="p">,</span> <span class="s2">"0"</span><span class="p">,</span> <span class="s2">"EmausBot"</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">,</span> <span class="mf">39.0</span><span class="p">,</span> <span class="mf">39.0</span><span class="p">,</span> <span class="mf">39.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">],</span> |
| <span class="p">[</span><span class="s2">"2013-01-01T00:00:00.000Z"</span><span class="p">,</span> <span class="s2">"0"</span><span class="p">,</span> <span class="s2">"article"</span><span class="p">,</span> <span class="s2">"0"</span><span class="p">,</span> <span class="s2">"0"</span><span class="p">,</span> <span class="s2">"112_U.S._580"</span><span class="p">,</span> <span class="s2">"en"</span><span class="p">,</span> <span class="s2">"1"</span><span class="p">,</span> <span class="s2">"MZMcBride"</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">,</span> <span class="mf">70.0</span><span class="p">,</span> <span class="mf">70.0</span><span class="p">,</span> <span class="mf">70.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">],</span> |
| <span class="p">[</span><span class="s2">"2013-01-01T00:00:00.000Z"</span><span class="p">,</span> <span class="s2">"0"</span><span class="p">,</span> <span class="s2">"article"</span><span class="p">,</span> <span class="s2">"0"</span><span class="p">,</span> <span class="s2">"0"</span><span class="p">,</span> <span class="s2">"113_U.S._243"</span><span class="p">,</span> <span class="s2">"en"</span><span class="p">,</span> <span class="s2">"1"</span><span class="p">,</span> <span class="s2">"MZMcBride"</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">,</span> <span class="mf">77.0</span><span class="p">,</span> <span class="mf">77.0</span><span class="p">,</span> <span class="mf">77.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">]</span> |
| <span class="p">]</span> |
| <span class="p">}</span> <span class="p">]</span> |
| </code></pre></div> |
| <h2 id="time-ordering">Time Ordering</h2> |
| |
| <p>The Scan query currently supports ordering based on timestamp for non-legacy queries. Note that using time ordering |
| will yield results that do not indicate which segment rows are from (<code>segmentId</code> will show up as <code>null</code>). Furthermore, |
| time ordering is only supported where the result set limit is less than <code>druid.query.scan.maxRowsQueuedForOrdering</code> |
| rows <strong>or</strong> all segments scanned have fewer than <code>druid.query.scan.maxSegmentPartitionsOrderedInMemory</code> partitions. Also, |
| time ordering is not supported for queries issued directly to historicals unless a list of segments is specified. The |
| reasoning behind these limitations is that the implementation of time ordering uses two strategies that can consume too |
| much heap memory if left unbounded. These strategies (listed below) are chosen on a per-Historical basis depending on |
| query result set limit and the number of segments being scanned.</p> |
| |
| <ol> |
| <li><p>Priority Queue: Each segment on a Historical is opened sequentially. Every row is added to a bounded priority |
| queue which is ordered by timestamp. For every row above the result set limit, the row with the earliest (if descending) |
| or latest (if ascending) timestamp will be dequeued. After every row has been processed, the sorted contents of the |
| priority queue are streamed back to the Broker(s) in batches. Attempting to load too many rows into memory runs the |
| risk of Historical nodes running out of memory. The <code>druid.query.scan.maxRowsQueuedForOrdering</code> property protects |
| from this by limiting the number of rows in the query result set when time ordering is used.</p></li> |
| <li><p>N-Way Merge: For each segment, each partition is opened in parallel. Since each partition's rows are already |
| time-ordered, an n-way merge can be performed on the results from each partition. This approach doesn't persist the entire |
| result set in memory (like the Priority Queue) as it streams back batches as they are returned from the merge function. |
| However, attempting to query too many partition could also result in high memory usage due to the need to open |
| decompression and decoding buffers for each. The <code>druid.query.scan.maxSegmentPartitionsOrderedInMemory</code> limit protects |
| from this by capping the number of partitions opened at any times when time ordering is used.</p></li> |
| </ol> |
| |
| <p>Both <code>druid.query.scan.maxRowsQueuedForOrdering</code> and <code>druid.query.scan.maxSegmentPartitionsOrderedInMemory</code> are |
| configurable and can be tuned based on hardware specs and number of dimensions being queried. These config properties |
| can also be overridden using the <code>maxRowsQueuedForOrdering</code> and <code>maxSegmentPartitionsOrderedInMemory</code> properties in |
| the query context (see the Query Context Properties section).</p> |
| |
| <h2 id="legacy-mode">Legacy mode</h2> |
| |
| <p>The Scan query supports a legacy mode designed for protocol compatibility with the former scan-query contrib extension. |
| In legacy mode you can expect the following behavior changes:</p> |
| |
| <ul> |
| <li>The <strong>time column is returned as "timestamp" rather than "</strong>time". This will take precedence over any other column |
| you may have that is named "timestamp".</li> |
| <li>The __time column is included in the list of columns even if you do not specifically ask for it.</li> |
| <li>Timestamps are returned as ISO8601 time strings rather than integers (milliseconds since 1970-01-01 00:00:00 UTC).</li> |
| </ul> |
| |
| <p>Legacy mode can be triggered either by passing <code>"legacy" : true</code> in your query JSON, or by setting |
| <code>druid.query.scan.legacy = true</code> on your Druid processes. If you were previously using the scan-query contrib extension, |
| the best way to migrate is to activate legacy mode during a rolling upgrade, then switch it off after the upgrade |
| is complete.</p> |
| |
| <h2 id="configuration-properties">Configuration Properties</h2> |
| |
| <p>Configuration properties:</p> |
| |
| <table><thead> |
| <tr> |
| <th>property</th> |
| <th>description</th> |
| <th>values</th> |
| <th>default</th> |
| </tr> |
| </thead><tbody> |
| <tr> |
| <td>druid.query.scan.maxRowsQueuedForOrdering</td> |
| <td>The maximum number of rows returned when time ordering is used</td> |
| <td>An integer in [1, 2147483647]</td> |
| <td>100000</td> |
| </tr> |
| <tr> |
| <td>druid.query.scan.maxSegmentPartitionsOrderedInMemory</td> |
| <td>The maximum number of segments scanned per historical when time ordering is used</td> |
| <td>An integer in [1, 2147483647]</td> |
| <td>50</td> |
| </tr> |
| <tr> |
| <td>druid.query.scan.legacy</td> |
| <td>Whether legacy mode should be turned on for Scan queries</td> |
| <td>true or false</td> |
| <td>false</td> |
| </tr> |
| </tbody></table> |
| |
| <h2 id="query-context-properties">Query Context Properties</h2> |
| |
| <table><thead> |
| <tr> |
| <th>property</th> |
| <th>description</th> |
| <th>values</th> |
| <th>default</th> |
| </tr> |
| </thead><tbody> |
| <tr> |
| <td>maxRowsQueuedForOrdering</td> |
| <td>The maximum number of rows returned when time ordering is used. Overrides the identically named config.</td> |
| <td>An integer in [1, 2147483647]</td> |
| <td><code>druid.query.scan.maxRowsQueuedForOrdering</code></td> |
| </tr> |
| <tr> |
| <td>maxSegmentPartitionsOrderedInMemory</td> |
| <td>The maximum number of segments scanned per historical when time ordering is used. Overrides the identically named config.</td> |
| <td>An integer in [1, 2147483647]</td> |
| <td><code>druid.query.scan.maxSegmentPartitionsOrderedInMemory</code></td> |
| </tr> |
| </tbody></table> |
| |
| <p>Sample query context JSON object:</p> |
| <div class="highlight"><pre><code class="language-json" data-lang="json"><span></span><span class="p">{</span> |
| <span class="nt">"maxRowsQueuedForOrdering"</span><span class="p">:</span> <span class="mi">100001</span><span class="p">,</span> |
| <span class="nt">"maxSegmentPartitionsOrderedInMemory"</span><span class="p">:</span> <span class="mi">100</span> |
| <span class="p">}</span> |
| </code></pre></div> |
| </div> |
| <div class="col-md-3"> |
| <div class="searchbox"> |
| <gcse:searchbox-only></gcse:searchbox-only> |
| </div> |
| <div id="toc" class="nav toc hidden-print"> |
| </div> |
| </div> |
| </div> |
| </div> |
| |
| <!-- Start page_footer include --> |
| <footer class="druid-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/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="GitHub" href="https://github.com/apache/druid" target="_blank"><span class="fab fa-github"></span></a> |
| </div> |
| <div class="text-center license"> |
| Copyright © 2020 <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> |
| |
| <script async src="https://www.googletagmanager.com/gtag/js?id=UA-131010415-1"></script> |
| <script> |
| window.dataLayer = window.dataLayer || []; |
| function gtag(){dataLayer.push(arguments);} |
| gtag('js', new Date()); |
| gtag('config', 'UA-131010415-1'); |
| </script> |
| <script> |
| function trackDownload(type, url) { |
| ga('send', 'event', 'download', type, url); |
| } |
| </script> |
| <script src="//code.jquery.com/jquery.min.js"></script> |
| <script src="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script> |
| <script src="/assets/js/druid.js"></script> |
| <!-- stop page_footer include --> |
| |
| |
| <script> |
| $(function() { |
| $(".toc").load("/docs/0.15.1-incubating/toc.html"); |
| |
| // There is no way to tell when .gsc-input will be async loaded into the page so just try to set a placeholder until it works |
| var tries = 0; |
| var timer = setInterval(function() { |
| tries++; |
| if (tries > 300) clearInterval(timer); |
| var searchInput = $('input.gsc-input'); |
| if (searchInput.length) { |
| searchInput.attr('placeholder', 'Search'); |
| clearInterval(timer); |
| } |
| }, 100); |
| }); |
| </script> |
| </body> |
| </html> |
