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id="main-content" class="vp-page"><!--[--><!----><!----><nav class="vp-breadcrumb disable"></nav><div class="vp-page-title"><h1><!---->查询性能分析</h1><div class="page-info"><!----><!----><span class="page-date-info" aria-label="写作日期📅" data-balloon-pos="up"><svg xmlns="http://www.w3.org/2000/svg" class="icon calendar-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="calendar icon" name="calendar"><path d="M716.4 110.137c0-18.753-14.72-33.473-33.472-33.473-18.753 0-33.473 14.72-33.473 33.473v33.473h66.993v-33.473zm-334.87 0c0-18.753-14.72-33.473-33.473-33.473s-33.52 14.72-33.52 33.473v33.473h66.993v-33.473zm468.81 33.52H716.4v100.465c0 18.753-14.72 33.473-33.472 33.473a33.145 33.145 0 01-33.473-33.473V143.657H381.53v100.465c0 18.753-14.72 33.473-33.473 33.473a33.145 33.145 0 01-33.473-33.473V143.657H180.6A134.314 134.314 0 0046.66 277.595v535.756A134.314 134.314 0 00180.6 947.289h669.74a134.36 134.36 0 00133.94-133.938V277.595a134.314 134.314 0 00-133.94-133.938zm33.473 267.877H147.126a33.145 33.145 0 01-33.473-33.473c0-18.752 14.72-33.473 33.473-33.473h736.687c18.752 0 33.472 14.72 33.472 33.473a33.145 33.145 0 01-33.472 33.473z"></path></svg><span data-allow-mismatch="text">2025/2/18</span><meta property="datePublished" content="2025-02-18T02:34:07.000Z"></span><!----><span class="page-reading-time-info" aria-label="阅读时间⌛" data-balloon-pos="up"><svg xmlns="http://www.w3.org/2000/svg" class="icon timer-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="timer icon" name="timer"><path d="M799.387 122.15c4.402-2.978 7.38-7.897 7.38-13.463v-1.165c0-8.933-7.38-16.312-16.312-16.312H256.33c-8.933 0-16.311 7.38-16.311 16.312v1.165c0 5.825 2.977 10.874 7.637 13.592 4.143 194.44 97.22 354.963 220.201 392.763-122.204 37.542-214.893 196.511-220.2 389.397-4.661 5.049-7.638 11.651-7.638 19.03v5.825h566.49v-5.825c0-7.379-2.849-13.981-7.509-18.9-5.049-193.016-97.867-351.985-220.2-389.527 123.24-37.67 216.446-198.453 220.588-392.892zM531.16 450.445v352.632c117.674 1.553 211.787 40.778 211.787 88.676H304.097c0-48.286 95.149-87.382 213.728-88.676V450.445c-93.077-3.107-167.901-81.297-167.901-177.093 0-8.803 6.99-15.793 15.793-15.793 8.803 0 15.794 6.99 15.794 15.793 0 80.261 63.69 145.635 142.01 145.635s142.011-65.374 142.011-145.635c0-8.803 6.99-15.793 15.794-15.793s15.793 6.99 15.793 15.793c0 95.019-73.789 172.82-165.96 177.093z"></path></svg><span>大约 12 分钟</span><meta property="timeRequired" content="PT12M"></span><!----><!----></div><hr></div><!----><div class="" vp-content><!----><div id="markdown-content"><h1 id="查询性能分析" tabindex="-1"><a class="header-anchor" href="#查询性能分析"><span>查询性能分析</span></a></h1><p>查询分析的意义在于帮助用户理解查询的执行机制和性能瓶颈，从而实现查询优化和性能提升。这不仅关乎到查询的执行效率，也直接影响到应用的用户体验和资源的有效利用。为了进行有效的查询分析，IoTDB 提供了查询分析语句：Explain 和 Explain Analyze。</p><ul><li>Explain 语句：允许用户预览查询 SQL 的执行计划，包括 IoTDB 如何组织数据检索和处理。</li><li>Explain Analyze 语句：在 Explain 语句基础上增加了性能分析，完整执行 SQL 并展示查询执行过程中的时间和资源消耗。为 IoTDB 用户深入理解查询详情以及进行查询优化提供了详细的相关信息。与其他常用的 IoTDB 排查手段相比，Explain Analyze 没有部署负担，同时能够针对单条 sql 进行分析，能够更好定位问题。各类方法对比如下：：</li></ul><table><thead><tr><th>方法</th><th>安装难度</th><th>业务影响</th><th>功能范围</th></tr></thead><tbody><tr><td>Explain Analyze语句</td><td>低。无需安装额外组件，为IoTDB内置SQL语句</td><td>低。只会影响当前分析的单条查询，对线上其他负载无影响</td><td>支持分布式，可支持对单条SQL进行追踪</td></tr><tr><td>监控面板</td><td>中。需要安装IoTDB监控面板工具（企业版工具），并开启IoTDB监控服务</td><td>中。IoTDB监控服务记录指标会带来额外耗时</td><td>支持分布式，仅支持对数据库整体查询负载和耗时进行分析</td></tr><tr><td>Arthas抽样</td><td>中。需要安装Java Arthas工具（部分内网无法直接安装Arthas，且安装后，有时需要重启应用）</td><td>高。CPU 抽样可能会影响线上业务的响应速度</td><td>不支持分布式，仅支持对数据库整体查询负载和耗时进行分析</td></tr></tbody></table><h2 id="_1-explain-语句" tabindex="-1"><a class="header-anchor" href="#_1-explain-语句"><span>1. Explain 语句</span></a></h2><h4 id="语法" tabindex="-1"><a class="header-anchor" href="#语法"><span>语法</span></a></h4><p>Explain命令允许用户查看SQL查询的执行计划。执行计划以算子的形式展示，描述了IoTDB会如何执行查询。其语法如下，其中SELECT_STATEMENT是查询相关的SQL语句：</p><div class="language-sql line-numbers-mode" data-highlighter="shiki" data-ext="sql" style="background-color:#282c34;color:#abb2bf;"><pre class="shiki one-dark-pro vp-code"><code class="language-sql"><span class="line"><span style="color:#ABB2BF;">EXPLAIN </span><span style="color:#56B6C2;">&lt;</span><span style="color:#ABB2BF;">SELECT_STATEMENT</span><span style="color:#56B6C2;">&gt;</span></span></code></pre><div class="line-numbers" aria-hidden="true" style="counter-reset:line-number 0;"><div class="line-number"></div></div></div><h4 id="含义" tabindex="-1"><a class="header-anchor" href="#含义"><span>含义</span></a></h4><div class="language-sql line-numbers-mode" data-highlighter="shiki" data-ext="sql" style="background-color:#282c34;color:#abb2bf;"><pre class="shiki one-dark-pro vp-code"><code class="language-sql"><span class="line"><span style="color:#7F848E;font-style:italic;">-- 创建数据库</span></span>
<span class="line"><span style="color:#C678DD;">create</span><span style="color:#C678DD;"> database</span><span style="color:#61AFEF;"> test</span><span style="color:#ABB2BF;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">-- 创建表</span></span>
<span class="line"><span style="color:#C678DD;">use</span><span style="color:#ABB2BF;"> test;</span></span>
<span class="line"><span style="color:#C678DD;">create</span><span style="color:#C678DD;"> table</span><span style="color:#61AFEF;"> t1</span><span style="color:#ABB2BF;"> (device_id STRING ID, </span><span style="color:#C678DD;">type</span><span style="color:#ABB2BF;"> STRING ATTRIBUTE, speed </span><span style="color:#C678DD;">float</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">-- 插入数据</span></span>
<span class="line"><span style="color:#C678DD;">insert into</span><span style="color:#ABB2BF;"> t1(device_id, </span><span style="color:#C678DD;">type</span><span style="color:#ABB2BF;">, speed) </span><span style="color:#C678DD;">values</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&#39;car_1&#39;</span><span style="color:#ABB2BF;">, </span><span style="color:#98C379;">&#39;Model Y&#39;</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">120</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"><span style="color:#C678DD;">insert into</span><span style="color:#ABB2BF;"> t1(device_id, </span><span style="color:#C678DD;">type</span><span style="color:#ABB2BF;">, speed) </span><span style="color:#C678DD;">values</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&#39;car_2&#39;</span><span style="color:#ABB2BF;">, </span><span style="color:#98C379;">&#39;Model 3&#39;</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">100</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">-- 执行 explain 语句</span></span>
<span class="line"><span style="color:#ABB2BF;">explain </span><span style="color:#C678DD;">select</span><span style="color:#ABB2BF;"> * </span><span style="color:#C678DD;">from</span><span style="color:#ABB2BF;"> t1;</span></span></code></pre><div class="line-numbers" aria-hidden="true" style="counter-reset:line-number 0;"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>执行上方SQL，会得到如下结果。不难看出，IoTDB 分别通过两个 TableScan 节点去不同的数据分区中获取表中的数据，最后通过Collect 算子汇总数据后返回。</p><div class="language-sql line-numbers-mode" data-highlighter="shiki" data-ext="sql" style="background-color:#282c34;color:#abb2bf;"><pre class="shiki one-dark-pro vp-code"><code class="language-sql"><span class="line"><span style="color:#ABB2BF;">+</span><span style="color:#7F848E;font-style:italic;">-----------------------------------------------------------------------------------------------+</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">distribution</span><span style="color:#ABB2BF;"> plan|</span></span>
<span class="line"><span style="color:#ABB2BF;">+</span><span style="color:#7F848E;font-style:italic;">-----------------------------------------------------------------------------------------------+</span></span>
<span class="line"><span style="color:#ABB2BF;">| ┌─────────────────────────────────────────────┐ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| │OutputNode-</span><span style="color:#D19A66;">4</span><span style="color:#ABB2BF;"> │ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| │OutputColumns-</span><span style="color:#E06C75;">[time, device_id, type, speed]</span><span style="color:#ABB2BF;"> │ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| │OutputSymbols: </span><span style="color:#E06C75;">[time, device_id, type, speed]</span><span style="color:#ABB2BF;">│ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| └─────────────────────────────────────────────┘ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| │ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| │ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| ┌─────────────────────────────────────────────┐ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| │Collect-</span><span style="color:#D19A66;">21</span><span style="color:#ABB2BF;"> │ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| │OutputSymbols: </span><span style="color:#E06C75;">[time, device_id, type, speed]</span><span style="color:#ABB2BF;">│ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| └─────────────────────────────────────────────┘ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| ┌───────────────────────┴───────────────────────┐ |</span></span>
<span class="line"><span style="color:#ABB2BF;">| │ │ |</span></span>
<span class="line"><span style="color:#ABB2BF;">|┌─────────────────────────────────────────────┐ ┌───────────┐ |</span></span>
<span class="line"><span style="color:#ABB2BF;">|│TableScan-</span><span style="color:#D19A66;">19</span><span style="color:#ABB2BF;"> │ │Exchange-</span><span style="color:#D19A66;">28</span><span style="color:#ABB2BF;">│ |</span></span>
<span class="line"><span style="color:#ABB2BF;">|│QualifiedTableName: </span><span style="color:#D19A66;">test</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">t1</span><span style="color:#ABB2BF;"> │ └───────────┘ |</span></span>
<span class="line"><span style="color:#ABB2BF;">|│OutputSymbols: </span><span style="color:#E06C75;">[time, device_id, type, speed]</span><span style="color:#ABB2BF;">│ │ |</span></span>
<span class="line"><span style="color:#ABB2BF;">|│DeviceNumber: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> │ │ |</span></span>
<span class="line"><span style="color:#ABB2BF;">|│ScanOrder: </span><span style="color:#C678DD;">ASC</span><span style="color:#ABB2BF;"> │ ┌─────────────────────────────────────────────┐|</span></span>
<span class="line"><span style="color:#ABB2BF;">|│PushDownOffset: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> │ │TableScan-</span><span style="color:#D19A66;">20</span><span style="color:#ABB2BF;"> │|</span></span>
<span class="line"><span style="color:#ABB2BF;">|│PushDownLimit: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> │ │QualifiedTableName: </span><span style="color:#D19A66;">test</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">t1</span><span style="color:#ABB2BF;"> │|</span></span>
<span class="line"><span style="color:#ABB2BF;">|│PushDownLimitToEachDevice: false │ │OutputSymbols: </span><span style="color:#E06C75;">[time, device_id, type, speed]</span><span style="color:#ABB2BF;">│|</span></span>
<span class="line"><span style="color:#ABB2BF;">|│RegionId: </span><span style="color:#D19A66;">2</span><span style="color:#ABB2BF;"> │ │DeviceNumber: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> │|</span></span>
<span class="line"><span style="color:#ABB2BF;">|└─────────────────────────────────────────────┘ │ScanOrder: </span><span style="color:#C678DD;">ASC</span><span style="color:#ABB2BF;"> │|</span></span>
<span class="line"><span style="color:#ABB2BF;">| │PushDownOffset: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> │|</span></span>
<span class="line"><span style="color:#ABB2BF;">| │PushDownLimit: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> │|</span></span>
<span class="line"><span style="color:#ABB2BF;">| │PushDownLimitToEachDevice: false │|</span></span>
<span class="line"><span style="color:#ABB2BF;">| │RegionId: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> │|</span></span>
<span class="line"><span style="color:#ABB2BF;">| └─────────────────────────────────────────────┘|</span></span>
<span class="line"><span style="color:#ABB2BF;">+</span><span style="color:#7F848E;font-style:italic;">-----------------------------------------------------------------------------------------------+</span></span></code></pre><div class="line-numbers" aria-hidden="true" style="counter-reset:line-number 0;"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="_2-explain-analyze-语句" tabindex="-1"><a class="header-anchor" href="#_2-explain-analyze-语句"><span>2. Explain Analyze 语句</span></a></h2><h4 id="语法-1" tabindex="-1"><a class="header-anchor" href="#语法-1"><span>语法</span></a></h4><div class="language-sql line-numbers-mode" data-highlighter="shiki" data-ext="sql" style="background-color:#282c34;color:#abb2bf;"><pre class="shiki one-dark-pro vp-code"><code class="language-sql"><span class="line"><span style="color:#ABB2BF;">EXPLAIN ANALYZE </span><span style="color:#E06C75;">[VERBOSE]</span><span style="color:#56B6C2;"> &lt;</span><span style="color:#ABB2BF;">SELECT_STATEMENT</span><span style="color:#56B6C2;">&gt;</span></span></code></pre><div class="line-numbers" aria-hidden="true" style="counter-reset:line-number 0;"><div class="line-number"></div></div></div><p>其中 SELECT_STATEMENT 对应需要分析的查询语句；VERBOSE为打印详细分析结果，不填写VERBOSE时EXPLAIN ANALYZE将会省略部分信息。</p><h4 id="含义-1" tabindex="-1"><a class="header-anchor" href="#含义-1"><span>含义</span></a></h4><p>Explain Analyze 是 IOTDB 查询引擎自带的性能分析 SQL，与 Explain 不同，它会执行对应的查询计划并统计执行信息，可以用于追踪一条查询的具体性能分布，用于对资源进行观察，进行性能调优与异常分析。</p><p>在 EXPLAIN ANALYZE 的结果集中，会包含如下信息：</p><figure><img src="/img/explain-analyze-1.png" alt="explain-analyze-1.png" tabindex="0" loading="lazy"><figcaption>explain-analyze-1.png</figcaption></figure><p>其中：</p><ul><li>QueryStatistics 包含查询层面进的统计信息，主要包含各规划阶段耗时，查询分片数量等信息。 <ul><li>Analyze Cost: SQL 分析阶段的耗时（包含 FetchPartitionCost 和 FetchSchemaCost）</li><li>Fetch Partition Cost：拉取分区表的耗时</li><li>Fetch Schema Cost：拉取元数据以及权限校验的耗时</li><li>Logical Plan Cost：构建逻辑计划的耗时</li><li>Logical Optimization Cost: 逻辑计划优化的耗时</li><li>Distribution Plan Cost：构建分布式计划的耗时</li><li>Fragment Instance Count：总的查询分片的数量，每个查询分片的信息会挨个输出</li></ul></li><li>FragmentInstance 是 IoTDB 一个查询分片的封装，每一个查询分片都会在结果集中输出一份分片的执行信息，主要包含 FragmentStatistics 和算子信息。FragmentStastistics 包含 Fragment 的统计信息，包括总实际耗时（墙上时间），所涉及到的 TsFile，调度信息等情况。在一个 Fragment 的信息输出同时会以节点树层级的方式展示该Fragment 下计划节点的统计信息，主要包括：CPU运行时间、输出的数据行数、指定接口被调用的次数、所占用的内存、节点专属的定制信息。 <ul><li>Total Wall Time: 该分片从开始执行到执行结束的物理时间</li><li>Cost of initDataQuerySource：构建查询文件列表</li><li>Seq File(unclosed): 未封口(memtable)的顺序文件数量, Seq File(closed): 封口的顺序文件数量</li><li>UnSeq File(unclosed): 未封口(memtable)的乱序文件数量, UnSeq File(closed): 未封口的乱序文件数量</li><li>ready queued time: 查询分片的所有task在 ready queue 中的总时长（task 未阻塞，但没有查询执行线程资源时，会被放入ready queue），blocked queued time: 查询分片的所有task在 bloced queue 中的总时长（task 因为某些资源，如内存，或者上游数据未发送过来，则会被放入blocked queue）</li><li>BloomFilter 相关（用于判断某个序列在tsfile中是否存在，存储于tsfile尾部） <ul><li>loadBloomFilterFromCacheCount: 命中BloomFilterCache的次数</li><li>loadBloomFilterFromDiskCount: 从磁盘中读取的次数</li><li>loadBloomFilterActualIOSize: 从磁盘中读取BloomFilter时耗费的磁盘IO（单位为bytes）</li><li>loadBloomFilterTime: 读取BloomFilter + 计算序列是否存在的总耗时（单位为ms）</li></ul></li><li>TimeSeriesMetadata 相关（序列在tsfile中的索引信息，一个序列在一个tsfile中只会存储一个） <ul><li>loadTimeSeriesMetadataDiskSeqCount: 从封口的顺序文件里加载出的TimeSeriesMetadata数量 <ul><li>大部分情况下等于Seq File(closed)，但如果有limit等算子，可能实际加载的数量会小于Seq File(closed)</li></ul></li><li>loadTimeSeriesMetadataDiskUnSeqCount: 从封口的乱序文件里加载出的TimeSeriesMetadata数量 <ul><li>大部分情况下等于UnSeq File(closed)，但如果有limit等算子，可能实际加载的数量会小于UnSeq File(closed)</li></ul></li><li>loadTimeSeriesMetadataDiskSeqTime: 从封口的顺序文件里加载TimeSeriesMetadata的耗时 <ul><li>并不是所有的 TimeSeriesMetadata 加载都涉及磁盘 IO，有可能会命中TimeSeriesMetadataCache，直接从缓存中读取，但输出信息里并没有分开统计这两者的耗时</li></ul></li><li>loadTimeSeriesMetadataDiskUnSeqTime: 从未封口的顺序文件里加载TimeSeriesMetadata的耗时</li><li>loadTimeSeriesMetadataFromCacheCount: 命中TimeSeriesMetadataCache的次数，注意这里对于对齐设备来讲，每个分量（包括time列，都会去单独请求Cache，所以对于对齐设备来讲，（loadTimeSeriesMetadataFromCacheCount + loadTimeSeriesMetadataFromDiskCount）= tsfile number * subSensor number(包括time列）</li><li>loadTimeSeriesMetadataFromDiskCount: 从磁盘中读取TimeSeriesMetadata的次数，一次读取会把该设备下查询所有涉及到的分量都读出来缓存在TimeSeriesMetadataCache中</li><li>loadTimeSeriesMetadataActualIOSize: 从磁盘中读取TimeSeriesMetadata时耗费的磁盘IO（单位为bytes）</li></ul></li><li>Mods 文件相关 <ul><li>TimeSeriesMetadataModificationTime: 读取mods文件花费的时间</li></ul></li><li>Chunk 相关 <ul><li>constructAlignedChunkReadersDiskCount: 读取已封口 tsfile 中总的 Chunk 数量</li><li>constructAlignedChunkReadersDiskTime: 读取已封口 tsfile 中 Chunk 的总耗时（包含磁盘IO和解压缩)</li><li>pageReadersDecodeAlignedDiskCount: 解编码已封口 tsfile 中总的 page 数量</li><li>pageReadersDecodeAlignedDiskTime: 解编码已封口 tsfile 中 page 的总耗时</li><li>loadChunkFromCacheCount: 命中ChunkCache的次数，注意这里对于对齐设备来讲，每个分量（包括time列，都会去单独请求Cache，所以对于对齐设备来讲，（loadChunkFromCacheCount + loadChunkFromDiskCount）= tsfile number * subSensor number(包括time列）* avg chunk number in each tsfile</li><li>loadChunkFromDiskCount: 从磁盘中读取Chunk的次数，一次只会读取一个分量，并缓存在ChunkCache中</li><li>loadChunkActualIOSize: 从磁盘中读取Chunk时耗费的磁盘IO（单位为bytes）</li></ul></li></ul></li></ul><h5 id="特别说明" tabindex="-1"><a class="header-anchor" href="#特别说明"><span>特别说明</span></a></h5><p>查询超时场景使用 Explain Analyze 语句：</p><p>Explain Analyze 本身是一种特殊的查询，所以当执行超时的时候，Explain Analyze 语句也无法正常返回结果。为了在查询超时的情况下也可以通过分析结果排查超时原因，Explain Analyze 提供了定时日志机制（无需用户配置），每经过一定的时间间隔会将 Explain Analyze 的当前结果以文本的形式输出到专门的日志中。当查询超时时，用户可以前往logs/log_explain_analyze.log中查看对应的日志进行排查。<br> 日志的时间间隔基于查询的超时时间进行计算，可以保证在超时的情况下至少会有两次的结果记录。</p><h5 id="示例" tabindex="-1"><a class="header-anchor" href="#示例"><span>示例</span></a></h5><p>下面是Explain Analyze的一个例子:</p><div class="language-sql line-numbers-mode" data-highlighter="shiki" data-ext="sql" style="background-color:#282c34;color:#abb2bf;"><pre class="shiki one-dark-pro vp-code"><code class="language-sql"><span class="line"><span style="color:#7F848E;font-style:italic;">-- 创建数据库</span></span>
<span class="line"><span style="color:#C678DD;">create</span><span style="color:#C678DD;"> database</span><span style="color:#61AFEF;"> test</span><span style="color:#ABB2BF;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">-- 创建表</span></span>
<span class="line"><span style="color:#C678DD;">use</span><span style="color:#ABB2BF;"> test;</span></span>
<span class="line"><span style="color:#C678DD;">create</span><span style="color:#C678DD;"> table</span><span style="color:#61AFEF;"> t1</span><span style="color:#ABB2BF;"> (device_id STRING ID, </span><span style="color:#C678DD;">type</span><span style="color:#ABB2BF;"> STRING ATTRIBUTE, speed </span><span style="color:#C678DD;">float</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">-- 插入数据</span></span>
<span class="line"><span style="color:#C678DD;">insert into</span><span style="color:#ABB2BF;"> t1(device_id, </span><span style="color:#C678DD;">type</span><span style="color:#ABB2BF;">, speed) </span><span style="color:#C678DD;">values</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&#39;car_1&#39;</span><span style="color:#ABB2BF;">, </span><span style="color:#98C379;">&#39;Model Y&#39;</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">120</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"><span style="color:#C678DD;">insert into</span><span style="color:#ABB2BF;"> t1(device_id, </span><span style="color:#C678DD;">type</span><span style="color:#ABB2BF;">, speed) </span><span style="color:#C678DD;">values</span><span style="color:#ABB2BF;">(</span><span style="color:#98C379;">&#39;car_2&#39;</span><span style="color:#ABB2BF;">, </span><span style="color:#98C379;">&#39;Model 3&#39;</span><span style="color:#ABB2BF;">, </span><span style="color:#D19A66;">100</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">);</span></span>
<span class="line"></span>
<span class="line"><span style="color:#7F848E;font-style:italic;">-- 执行 explain analyze 语句</span></span>
<span class="line"><span style="color:#ABB2BF;">explain analyze </span><span style="color:#C678DD;">verbose</span><span style="color:#C678DD;"> select</span><span style="color:#ABB2BF;"> * </span><span style="color:#C678DD;">from</span><span style="color:#ABB2BF;"> t1;</span></span></code></pre><div class="line-numbers" aria-hidden="true" style="counter-reset:line-number 0;"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>得到输出如下：</p><div class="language-sql line-numbers-mode" data-highlighter="shiki" data-ext="sql" style="background-color:#282c34;color:#abb2bf;"><pre class="shiki one-dark-pro vp-code"><code class="language-sql"><span class="line"><span style="color:#ABB2BF;">+</span><span style="color:#7F848E;font-style:italic;">-----------------------------------------------------------------------------------------------+</span></span>
<span class="line"><span style="color:#ABB2BF;">| Explain Analyze|</span></span>
<span class="line"><span style="color:#ABB2BF;">+</span><span style="color:#7F848E;font-style:italic;">-----------------------------------------------------------------------------------------------+</span></span>
<span class="line"><span style="color:#ABB2BF;">|Analyze Cost: </span><span style="color:#D19A66;">38</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">860</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">|</span><span style="color:#C678DD;">Fetch</span><span style="color:#C678DD;"> Partition</span><span style="color:#ABB2BF;"> Cost: </span><span style="color:#D19A66;">9</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">888</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">|</span><span style="color:#C678DD;">Fetch</span><span style="color:#C678DD;"> Schema</span><span style="color:#ABB2BF;"> Cost: </span><span style="color:#D19A66;">54</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">046</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">|Logical Plan Cost: </span><span style="color:#D19A66;">10</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">102</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">|Logical Optimization Cost: </span><span style="color:#D19A66;">17</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">396</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">|</span><span style="color:#C678DD;">Distribution</span><span style="color:#ABB2BF;"> Plan Cost: </span><span style="color:#D19A66;">2</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">508</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">|Dispatch Cost: </span><span style="color:#D19A66;">22</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">126</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">|Fragment Instances Count: </span><span style="color:#D19A66;">2</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| |</span></span>
<span class="line"><span style="color:#ABB2BF;">|FRAGMENT-INSTANCE</span><span style="color:#E06C75;">[Id: 20241127_090849_00009_1.2.0][IP: 0.0.0.0][DataRegion: 2][State: FINISHED]</span><span style="color:#ABB2BF;">|</span></span>
<span class="line"><span style="color:#ABB2BF;">| Total Wall </span><span style="color:#C678DD;">Time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">18</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Cost of initDataQuerySource: </span><span style="color:#D19A66;">6</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">153</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Seq </span><span style="color:#C678DD;">File</span><span style="color:#ABB2BF;">(unclosed): </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;">, Seq </span><span style="color:#C678DD;">File</span><span style="color:#ABB2BF;">(closed): </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| UnSeq </span><span style="color:#C678DD;">File</span><span style="color:#ABB2BF;">(unclosed): </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">, UnSeq </span><span style="color:#C678DD;">File</span><span style="color:#ABB2BF;">(closed): </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| ready queued </span><span style="color:#C678DD;">time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">164</span><span style="color:#ABB2BF;"> ms, blocked queued </span><span style="color:#C678DD;">time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">342</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Query </span><span style="color:#C678DD;">Statistics</span><span style="color:#ABB2BF;">: |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadBloomFilterFromCacheCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadBloomFilterFromDiskCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadBloomFilterActualIOSize: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadBloomFilterTime: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">000</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadTimeSeriesMetadataAlignedMemSeqCount: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadTimeSeriesMetadataAlignedMemSeqTime: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">246</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadTimeSeriesMetadataFromCacheCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadTimeSeriesMetadataFromDiskCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadTimeSeriesMetadataActualIOSize: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| constructAlignedChunkReadersMemCount: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| constructAlignedChunkReadersMemTime: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">294</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadChunkFromCacheCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadChunkFromDiskCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadChunkActualIOSize: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| pageReadersDecodeAlignedMemCount: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| pageReadersDecodeAlignedMemTime: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">047</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#E06C75;">[PlanNodeId 43]</span><span style="color:#ABB2BF;">: IdentitySinkNode(IdentitySinkOperator) |</span></span>
<span class="line"><span style="color:#ABB2BF;">| CPU </span><span style="color:#C678DD;">Time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">5</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">523</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">output</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">2</span><span style="color:#C678DD;"> rows</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| HasNext() Called Count: </span><span style="color:#D19A66;">6</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">Next</span><span style="color:#ABB2BF;">() Called Count: </span><span style="color:#D19A66;">5</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Estimated Memory </span><span style="color:#C678DD;">Size</span><span style="color:#ABB2BF;">: : </span><span style="color:#D19A66;">327680</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#E06C75;">[PlanNodeId 31]</span><span style="color:#ABB2BF;">: CollectNode(CollectOperator) |</span></span>
<span class="line"><span style="color:#ABB2BF;">| CPU </span><span style="color:#C678DD;">Time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">5</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">512</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">output</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">2</span><span style="color:#C678DD;"> rows</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| HasNext() Called Count: </span><span style="color:#D19A66;">6</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">Next</span><span style="color:#ABB2BF;">() Called Count: </span><span style="color:#D19A66;">5</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Estimated Memory </span><span style="color:#C678DD;">Size</span><span style="color:#ABB2BF;">: : </span><span style="color:#D19A66;">327680</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#E06C75;">[PlanNodeId 29]</span><span style="color:#ABB2BF;">: TableScanNode(TableScanOperator) |</span></span>
<span class="line"><span style="color:#ABB2BF;">| CPU </span><span style="color:#C678DD;">Time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">5</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">439</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">output</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">1</span><span style="color:#C678DD;"> rows</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| HasNext() Called Count: </span><span style="color:#D19A66;">3</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">Next</span><span style="color:#ABB2BF;">() Called Count: </span><span style="color:#D19A66;">2</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Estimated Memory </span><span style="color:#C678DD;">Size</span><span style="color:#ABB2BF;">: : </span><span style="color:#D19A66;">327680</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| DeviceNumber: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| CurrentDeviceIndex: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#E06C75;">[PlanNodeId 40]</span><span style="color:#ABB2BF;">: ExchangeNode(ExchangeOperator) |</span></span>
<span class="line"><span style="color:#ABB2BF;">| CPU </span><span style="color:#C678DD;">Time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">053</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">output</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">1</span><span style="color:#C678DD;"> rows</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| HasNext() Called Count: </span><span style="color:#D19A66;">2</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">Next</span><span style="color:#ABB2BF;">() Called Count: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Estimated Memory </span><span style="color:#C678DD;">Size</span><span style="color:#ABB2BF;">: : </span><span style="color:#D19A66;">131072</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| |</span></span>
<span class="line"><span style="color:#ABB2BF;">|FRAGMENT-INSTANCE</span><span style="color:#E06C75;">[Id: 20241127_090849_00009_1.3.0][IP: 0.0.0.0][DataRegion: 1][State: FINISHED]</span><span style="color:#ABB2BF;">|</span></span>
<span class="line"><span style="color:#ABB2BF;">| Total Wall </span><span style="color:#C678DD;">Time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">13</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Cost of initDataQuerySource: </span><span style="color:#D19A66;">5</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">725</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Seq </span><span style="color:#C678DD;">File</span><span style="color:#ABB2BF;">(unclosed): </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;">, Seq </span><span style="color:#C678DD;">File</span><span style="color:#ABB2BF;">(closed): </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| UnSeq </span><span style="color:#C678DD;">File</span><span style="color:#ABB2BF;">(unclosed): </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">, UnSeq </span><span style="color:#C678DD;">File</span><span style="color:#ABB2BF;">(closed): </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| ready queued </span><span style="color:#C678DD;">time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">118</span><span style="color:#ABB2BF;"> ms, blocked queued </span><span style="color:#C678DD;">time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">5</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">844</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Query </span><span style="color:#C678DD;">Statistics</span><span style="color:#ABB2BF;">: |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadBloomFilterFromCacheCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadBloomFilterFromDiskCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadBloomFilterActualIOSize: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadBloomFilterTime: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">000</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadTimeSeriesMetadataAlignedMemSeqCount: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadTimeSeriesMetadataAlignedMemSeqTime: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">004</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadTimeSeriesMetadataFromCacheCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadTimeSeriesMetadataFromDiskCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadTimeSeriesMetadataActualIOSize: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| constructAlignedChunkReadersMemCount: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| constructAlignedChunkReadersMemTime: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">001</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadChunkFromCacheCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadChunkFromDiskCount: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| loadChunkActualIOSize: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| pageReadersDecodeAlignedMemCount: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| pageReadersDecodeAlignedMemTime: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">007</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#E06C75;">[PlanNodeId 42]</span><span style="color:#ABB2BF;">: IdentitySinkNode(IdentitySinkOperator) |</span></span>
<span class="line"><span style="color:#ABB2BF;">| CPU </span><span style="color:#C678DD;">Time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">270</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">output</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">1</span><span style="color:#C678DD;"> rows</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| HasNext() Called Count: </span><span style="color:#D19A66;">3</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">Next</span><span style="color:#ABB2BF;">() Called Count: </span><span style="color:#D19A66;">2</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Estimated Memory </span><span style="color:#C678DD;">Size</span><span style="color:#ABB2BF;">: : </span><span style="color:#D19A66;">327680</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#E06C75;">[PlanNodeId 30]</span><span style="color:#ABB2BF;">: TableScanNode(TableScanOperator) |</span></span>
<span class="line"><span style="color:#ABB2BF;">| CPU </span><span style="color:#C678DD;">Time</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;">.</span><span style="color:#D19A66;">250</span><span style="color:#ABB2BF;"> ms |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">output</span><span style="color:#ABB2BF;">: </span><span style="color:#D19A66;">1</span><span style="color:#C678DD;"> rows</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| HasNext() Called Count: </span><span style="color:#D19A66;">3</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| </span><span style="color:#C678DD;">Next</span><span style="color:#ABB2BF;">() Called Count: </span><span style="color:#D19A66;">2</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| Estimated Memory </span><span style="color:#C678DD;">Size</span><span style="color:#ABB2BF;">: : </span><span style="color:#D19A66;">327680</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| DeviceNumber: </span><span style="color:#D19A66;">1</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">| CurrentDeviceIndex: </span><span style="color:#D19A66;">0</span><span style="color:#ABB2BF;"> |</span></span>
<span class="line"><span style="color:#ABB2BF;">+</span><span style="color:#7F848E;font-style:italic;">-----------------------------------------------------------------------------------------------+</span></span></code></pre><div class="line-numbers" aria-hidden="true" style="counter-reset:line-number 0;"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="_3-常见问题" tabindex="-1"><a class="header-anchor" href="#_3-常见问题"><span>3. 常见问题</span></a></h2><h4 id="_1-wall-time-墙上时间-和-cpu-time-cpu时间-的区别" tabindex="-1"><a class="header-anchor" href="#_1-wall-time-墙上时间-和-cpu-time-cpu时间-的区别"><span>1. WALL TIME（墙上时间）和 CPU TIME（CPU时间）的区别？</span></a></h4><p>CPU 时间也称为处理器时间或处理器使用时间，指的是程序在执行过程中实际占用 CPU 进行计算的时间，显示的是程序实际消耗的处理器资源。</p><p>墙上时间也称为实际时间或物理时间，指的是从程序开始执行到程序结束的总时间，包括了所有等待时间。。</p><ol><li>WALL TIME &lt; CPU TIME 的场景：比如一个查询分片最后被调度器使用两个线程并行执行，真实物理世界上是 10s 过去了，但两个线程，可能一直占了两个 cpu 核跑了 10s，那 cpu time 就是 20s，wall time就是 10s</li><li>WALL TIME &gt; CPU TIME 的场景：因为系统内可能会存在多个查询并行执行，但查询的执行线程数和内存是固定的， <ol><li>所以当查询分片被某些资源阻塞住时（比如没有足够的内存进行数据传输、或等待上游数据）就会放入Blocked Queue，此时查询分片并不会占用 CPU TIME，但WALL TIME（真实物理时间的时间）是在向前流逝的</li><li>或者当查询线程资源不足时，比如当前共有16个查询线程，但系统内并发有20个查询分片，即使所有查询都没有被阻塞，也只会同时并行运行16个查询分片，另外四个会被放入 READY QUEUE，等待被调度执行，此时查询分片并不会占用 CPU TIME，但WALL TIME（真实物理时间的时间）是在向前流逝的</li></ol></li></ol><h4 id="_2-explain-analyze-是否有额外开销-测出的耗时是否与查询真实执行时有差别" tabindex="-1"><a class="header-anchor" href="#_2-explain-analyze-是否有额外开销-测出的耗时是否与查询真实执行时有差别"><span>2. Explain Analyze 是否有额外开销，测出的耗时是否与查询真实执行时有差别？</span></a></h4><p>几乎没有，因为 explain analyze operator 是单独的线程执行，收集原查询的统计信息，且这些统计信息，即使不explain analyze，原来的查询也会生成，只是没有人去取。并且 explain analyze 是纯 next 遍历结果集，不会打印，所以与原来查询真实执行时的耗时不会有显著差别。</p><h4 id="_3-io-耗时主要关注几个指标" tabindex="-1"><a class="header-anchor" href="#_3-io-耗时主要关注几个指标"><span>3. IO 耗时主要关注几个指标？</span></a></h4><p>涉及 IO 耗时的指标主要有：loadBloomFilterActualIOSize, loadBloomFilterTime, loadTimeSeriesMetadataAlignedDisk[Seq/Unseq]Time, loadTimeSeriesMetadataActualIOSize, alignedTimeSeriesMetadataModificationTime, constructAlignedChunkReadersDiskTime, loadChunkActualIOSize，各指标的具体含义见上文。<br> TimeSeriesMetadata 的加载分别统计了顺序和乱序文件，但 Chunk 的读取暂时未分开统计，但顺乱序比例可以通过TimeseriesMetadata 顺乱序的比例计算出来。</p><h4 id="_4-乱序数据对查询性能的影响能否有一些指标展示出来" tabindex="-1"><a class="header-anchor" href="#_4-乱序数据对查询性能的影响能否有一些指标展示出来"><span>4. 乱序数据对查询性能的影响能否有一些指标展示出来？</span></a></h4><p>乱序数据产生的影响主要有两个：</p><ol><li>需要在内存中多做一个归并排序（一般认为这个耗时是比较短的，毕竟是纯内存的 cpu 操作）</li><li>乱序数据会产生数据块间的时间范围重叠，导致统计信息无法使用 <ol><li>无法利用统计信息直接 skip 掉整个不满足值过滤要求的 chunk <ol><li>一般用户的查询都是只包含时间过滤条件，则不会有影响</li></ol></li><li>无法利用统计信息直接计算出聚合值，无需读取数据</li></ol></li></ol><p>单独对于乱序数据的性能影响，目前并没有有效的观测手段，除非就是在有乱序数据的时候，执行一遍查询耗时，然后等乱序合完了，再执行一遍，才能对比出来。</p><p>因为即使乱序这部分数据进了顺序，也是需要 IO、加压缩、decode，这个耗时少不了，不会因为乱序数据被合并进乱序了，就减少了。</p><h4 id="_5-执行-explain-analyze-时-查询超时后-为什么结果没有输出在-log-explain-analyze-log-中" tabindex="-1"><a class="header-anchor" href="#_5-执行-explain-analyze-时-查询超时后-为什么结果没有输出在-log-explain-analyze-log-中"><span>5. 执行 explain analyze 时，查询超时后，为什么结果没有输出在 log_explain_analyze.log 中？</span></a></h4><p>升级时，只替换了 lib 包，没有替换 conf/logback-datanode.xml，需要替换一下 conf/logback-datanode.xml，然后不需要重启（该文件内容可以被热加载），大约等待 1 分钟后，重新执行 explain analyze verbose。</p></div><!----><!----><!----></div><footer class="vp-page-meta"><div class="vp-meta-item edit-link"><a class="auto-link external-link vp-meta-label" href="https://github.com/apache/iotdb-docs/edit/main/src/zh/UserGuide/latest-Table/User-Manual/Query-Performance-Analysis.md" aria-label="发现错误？在 GitHub 上编辑此页" rel="noopener noreferrer" target="_blank"><!--[--><svg xmlns="http://www.w3.org/2000/svg" class="icon edit-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="edit icon" name="edit"><path d="M430.818 653.65a60.46 60.46 0 0 1-50.96-93.281l71.69-114.012 7.773-10.365L816.038 80.138A60.46 60.46 0 0 1 859.225 62a60.46 60.46 0 0 1 43.186 18.138l43.186 43.186a60.46 60.46 0 0 1 0 86.373L588.879 565.55l-8.637 8.637-117.466 68.234a60.46 60.46 0 0 1-31.958 11.229z"></path><path d="M728.802 962H252.891A190.883 190.883 0 0 1 62.008 771.98V296.934a190.883 190.883 0 0 1 190.883-192.61h267.754a60.46 60.46 0 0 1 0 120.92H252.891a69.962 69.962 0 0 0-69.098 69.099V771.98a69.962 69.962 0 0 0 69.098 69.098h475.911A69.962 69.962 0 0 0 797.9 771.98V503.363a60.46 60.46 0 1 1 120.922 0V771.98A190.883 190.883 0 0 1 728.802 962z"></path></svg><!--]-->发现错误？在 GitHub 上编辑此页<!----></a></div><div class="vp-meta-item git-info"><div class="update-time"><span class="vp-meta-label">最近更新: </span><time class="vp-meta-info" datetime="2025-03-04T06:04:48.000Z" data-allow-mismatch>2025/3/4 06:04</time></div><!----></div></footer><nav class="vp-page-nav"><!----><a class="route-link auto-link next" href="/zh/UserGuide/latest-Table/User-Manual/Load-Balance.html" aria-label="集群维护"><div class="hint">下一页<span class="arrow end"></span></div><div class="link">集群维护<!----></div></a></nav><!----><!----><!--]--></main><!--]--><footer class="site-footer"><span id="doc-version" style="display:none;">latest-Table</span><p class="copyright-text">版权所有 © 2026 Apache软件基金会。
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