| import{_ as a,o as n,c as e,a as t,f as s}from"./app-wIgiOADQ.js";const o={},r=s(`<h2 id="influxdb-protocol" tabindex="-1"><a class="header-anchor" href="#influxdb-protocol" aria-hidden="true">#</a> InfluxDB-Protocol</h2><h3 id="_1-切换方案" tabindex="-1"><a class="header-anchor" href="#_1-切换方案" aria-hidden="true">#</a> 1.切换方案</h3><p>假如您原先接入 InfluxDB 的业务代码如下:</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">InfluxDB</span> influxDB <span class="token operator">=</span> <span class="token class-name">InfluxDBFactory</span><span class="token punctuation">.</span><span class="token function">connect</span><span class="token punctuation">(</span>openurl<span class="token punctuation">,</span> username<span class="token punctuation">,</span> password<span class="token punctuation">)</span><span class="token punctuation">;</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>您只需要将 InfluxDBFactory 替换为 <strong>IoTDBInfluxDBFactory</strong> 即可实现业务向 IoTDB 的切换:</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">InfluxDB</span> influxDB <span class="token operator">=</span> <span class="token class-name">IoTDBInfluxDBFactory</span><span class="token punctuation">.</span><span class="token function">connect</span><span class="token punctuation">(</span>openurl<span class="token punctuation">,</span> username<span class="token punctuation">,</span> password<span class="token punctuation">)</span><span class="token punctuation">;</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><h3 id="_2-方案设计" tabindex="-1"><a class="header-anchor" href="#_2-方案设计" aria-hidden="true">#</a> 2.方案设计</h3><h4 id="_2-1-influxdb-protocol适配器" tabindex="-1"><a class="header-anchor" href="#_2-1-influxdb-protocol适配器" aria-hidden="true">#</a> 2.1 InfluxDB-Protocol适配器</h4><p>该适配器以 IoTDB Java Session 接口为底层基础,实现了 InfluxDB 的 Java 接口 <code>interface InfluxDB</code>,对用户提供了所有 InfluxDB 的接口方法,最终用户可以无感知地使用 InfluxDB 协议向 IoTDB 发起写入和读取请求。</p><figure><img src="https://alioss.timecho.com/docs/img/UserGuide/API/IoTDB-InfluxDB/architecture-design.png?raw=true" alt="architecture-design" tabindex="0" loading="lazy"><figcaption>architecture-design</figcaption></figure><figure><img src="https://alioss.timecho.com/docs/img/UserGuide/API/IoTDB-InfluxDB/class-diagram.png?raw=true" alt="class-diagram" tabindex="0" loading="lazy"><figcaption>class-diagram</figcaption></figure><h4 id="_2-2-元数据格式转换" tabindex="-1"><a class="header-anchor" href="#_2-2-元数据格式转换" aria-hidden="true">#</a> 2.2 元数据格式转换</h4><p>InfluxDB 的元数据是 tag-field 模型,IoTDB 的元数据是树形模型。为了使适配器能够兼容 InfluxDB 协议,需要把 InfluxDB 的元数据模型转换成 IoTDB 的元数据模型。</p><h5 id="_2-2-1-influxdb-元数据" tabindex="-1"><a class="header-anchor" href="#_2-2-1-influxdb-元数据" aria-hidden="true">#</a> 2.2.1 InfluxDB 元数据</h5><ol><li>database: 数据库名。</li><li>measurement: 测量指标名。</li><li>tags : 各种有索引的属性。</li><li>fields : 各种记录值(没有索引的属性)。</li></ol><figure><img src="https://alioss.timecho.com/docs/img/UserGuide/API/IoTDB-InfluxDB/influxdb-data.png?raw=true" alt="influxdb-data" tabindex="0" loading="lazy"><figcaption>influxdb-data</figcaption></figure><h5 id="_2-2-2-iotdb-元数据" tabindex="-1"><a class="header-anchor" href="#_2-2-2-iotdb-元数据" aria-hidden="true">#</a> 2.2.2 IoTDB 元数据</h5><ol><li>storage group: 存储组。</li><li>path(time series ID):存储路径。</li><li>measurement: 物理量。</li></ol><figure><img src="https://alioss.timecho.com/docs/img/UserGuide/API/IoTDB-InfluxDB/iotdb-data.png?raw=true" alt="iotdb-data" tabindex="0" loading="lazy"><figcaption>iotdb-data</figcaption></figure><h5 id="_2-2-3-两者映射关系" tabindex="-1"><a class="header-anchor" href="#_2-2-3-两者映射关系" aria-hidden="true">#</a> 2.2.3 两者映射关系</h5><p>InfluxDB 元数据和 IoTDB 元数据有着如下的映射关系:</p><ol><li>InfluxDB 中的 database 和 measurement 组合起来作为 IoTDB 中的 storage group。</li><li>InfluxDB 中的 field key 作为 IoTDB 中 measurement 路径,InfluxDB 中的 field value 即是该路径下记录的测点值。</li><li>InfluxDB 中的 tag 在 IoTDB 中使用 storage group 和 measurement 之间的路径表达。InfluxDB 的 tag key 由 storage group 和 measurement 之间路径的顺序隐式表达,tag value 记录为对应顺序的路径的名称。</li></ol><p>InfluxDB 元数据向 IoTDB 元数据的转换关系可以由下面的公示表示:</p><p><code>root.{database}.{measurement}.{tag value 1}.{tag value 2}...{tag value N-1}.{tag value N}.{field key}</code></p><figure><img src="https://alioss.timecho.com/docs/img/UserGuide/API/IoTDB-InfluxDB/influxdb-vs-iotdb-data.png?raw=true" alt="influxdb-vs-iotdb-data" tabindex="0" loading="lazy"><figcaption>influxdb-vs-iotdb-data</figcaption></figure><p>如上图所示,可以看出:</p><p>我们在 IoTDB 中使用 storage group 和 measurement 之间的路径来表达 InfluxDB tag 的概念,也就是图中右侧绿色方框的部分。</p><p>storage group 和 measurement 之间的每一层都代表一个 tag。如果 tag key 的数量为 N,那么 storage group 和 measurement 之间的路径的层数就是 N。我们对 storage group 和 measurement 之间的每一层进行顺序编号,每一个序号都和一个 tag key 一一对应。同时,我们使用 storage group 和 measurement 之间每一层 <strong>路径的名字</strong> 来记 tag value,tag key 可以通过自身的序号找到对应路径层级下的 tag value.</p><h5 id="_2-2-4-关键问题" tabindex="-1"><a class="header-anchor" href="#_2-2-4-关键问题" aria-hidden="true">#</a> 2.2.4 关键问题</h5><p>在 InfluxDB 的 SQL 语句中,tag 出现的顺序的不同并不会影响实际的执行结果。</p><p>例如:<code>insert factory, workshop=A1, production=B1 temperature=16.9</code> 和 <code>insert factory, production=B1, workshop=A1 temperature=16.9</code> 两条 InfluxDB SQL 的含义(以及执行结果)相等。</p><p>但在 IoTDB 中,上述插入的数据点可以存储在 <code>root.monitor.factory.A1.B1.temperature</code> 下,也可以存储在 <code>root.monitor.factory.B1.A1.temperature</code> 下。因此,IoTDB 路径中储存的 InfluxDB 的 tag 的顺序是需要被特别考虑的,因为 <code>root.monitor.factory.A1.B1.temperature</code> 和<br><code>root.monitor.factory.B1.A1.temperature</code> 是两条不同的序列。我们可以认为,IoTDB 元数据模型对 tag 顺序的处理是“敏感”的。</p><p>基于上述的考虑,我们还需要在 IoTDB 中记录 InfluxDB 每个 tag 对应在 IoTDB 路径中的层级顺序,以确保在执行 InfluxDB SQL 时,不论 InfluxDB SQL 中 tag 出现的顺序如何,只要该 SQL 表达的是对同一个时间序列上的操作,那么适配器都可以唯一对应到 IoTDB 中的一条时间序列上进行操作。</p><p>这里还需要考虑的另一个问题是:InfluxDB 的 tag key 及对应顺序关系应该如何持久化到 IoTDB 数据库中,以确保不会丢失相关信息。</p><p><strong>解决方案:</strong></p><p><strong>tag key 对应顺序关系在内存中的形式</strong></p><p>通过利用内存中的<code>Map<Measurement, Map<Tag Key, Order>></code> 这样一个 Map 结构,来维护 tag 在 IoTDB 路径层级上的顺序。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code> <span class="token class-name">Map</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">,</span> <span class="token class-name">Map</span><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">,</span> <span class="token class-name">Integer</span><span class="token punctuation">></span><span class="token punctuation">></span></span> measurementTagOrder |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>可以看出 Map 是一个两层的结构。</p><p>第一层的 Key 是 String 类型的 InfluxDB measurement,第一层的 Value 是一个 <String, Integer> 结构的 Map。</p><p>第二层的 Key 是 String 类型的 InfluxDB tag key,第二层的 Value 是 Integer 类型的 tag order,也就是 tag 在 IoTDB 路径层级上的顺序。</p><p>使用时,就可以先通过 InfluxDB measurement 定位,再通过 InfluxDB tag key 定位,最后就可以获得 tag 在 IoTDB 路径层级上的顺序了。</p><p><strong>tag key 对应顺序关系的持久化方案</strong></p><p>存储组为<code>root.TAG_INFO</code>,分别用存储组下的 <code>database_name</code>, <code>measurement_name</code>, <code>tag_name</code> 和 <code>tag_order</code> 测点来存储 tag key 极其对应的顺序关系。</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>+-----------------------------+---------------------------+------------------------------+----------------------+-----------------------+ |
| | Time|root.TAG_INFO.database_name|root.TAG_INFO.measurement_name|root.TAG_INFO.tag_name|root.TAG_INFO.tag_order| |
| +-----------------------------+---------------------------+------------------------------+----------------------+-----------------------+ |
| |2021-10-12T01:21:26.907+08:00| monitor| factory| workshop| 1| |
| |2021-10-12T01:21:27.310+08:00| monitor| factory| production| 2| |
| |2021-10-12T01:21:27.313+08:00| monitor| factory| cell| 3| |
| |2021-10-12T01:21:47.314+08:00| building| cpu| tempture| 1| |
| +-----------------------------+---------------------------+------------------------------+----------------------+-----------------------+ |
| </code></pre><div class="line-numbers" aria-hidden="true"><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><h4 id="_2-3-实例" tabindex="-1"><a class="header-anchor" href="#_2-3-实例" aria-hidden="true">#</a> 2.3 实例</h4><h5 id="_2-3-1-插入数据" tabindex="-1"><a class="header-anchor" href="#_2-3-1-插入数据" aria-hidden="true">#</a> 2.3.1 插入数据</h5><ol><li><p>假定按照以下的顺序插入三条数据到 InfluxDB 中 (database=monitor):</p><p>(1)<code>insert student,name=A,phone=B,sex=C score=99</code></p><p>(2)<code>insert student,address=D score=98</code></p><p>(3)<code>insert student,name=A,phone=B,sex=C,address=D score=97</code></p></li><li><p>简单对上述 InfluxDB 的时序进行解释,database 是 monitor; measurement 是student;tag 分别是 name,phone、sex 和 address;field 是 score。</p></li></ol><p>对应的InfluxDB的实际存储为:</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>time address name phone sex socre |
| ---- ------- ---- ----- --- ----- |
| 1633971920128182000 A B C 99 |
| 1633971947112684000 D 98 |
| 1633971963011262000 D A B C 97 |
| </code></pre><div class="line-numbers" aria-hidden="true"><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><ol start="3"><li><p>IoTDB顺序插入三条数据的过程如下:</p><p>(1)插入第一条数据时,需要将新出现的三个 tag key 更新到 table 中,IoTDB 对应的记录 tag 顺序的 table 为:</p><table><thead><tr><th>database</th><th>measurement</th><th>tag_key</th><th>Order</th></tr></thead><tbody><tr><td>monitor</td><td>student</td><td>name</td><td>0</td></tr><tr><td>monitor</td><td>student</td><td>phone</td><td>1</td></tr><tr><td>monitor</td><td>student</td><td>sex</td><td>2</td></tr></tbody></table><p>(2)插入第二条数据时,由于此时记录 tag 顺序的 table 中已经有了三个 tag key,因此需要将出现的第四个 tag key=address 更新记录。IoTDB 对应的记录 tag 顺序的 table 为:</p><table><thead><tr><th>database</th><th>measurement</th><th>tag_key</th><th>order</th></tr></thead><tbody><tr><td>monitor</td><td>student</td><td>name</td><td>0</td></tr><tr><td>monitor</td><td>student</td><td>phone</td><td>1</td></tr><tr><td>monitor</td><td>student</td><td>sex</td><td>2</td></tr><tr><td>monitor</td><td>student</td><td>address</td><td>3</td></tr></tbody></table><p>(3)插入第三条数据时,此时四个 tag key 都已经记录过,所以不需要更新记录,IoTDB 对应的记录 tag 顺序的 table 为:</p><table><thead><tr><th>database</th><th>measurement</th><th>tag_key</th><th>order</th></tr></thead><tbody><tr><td>monitor</td><td>student</td><td>name</td><td>0</td></tr><tr><td>monitor</td><td>student</td><td>phone</td><td>1</td></tr><tr><td>monitor</td><td>student</td><td>sex</td><td>2</td></tr><tr><td>monitor</td><td>student</td><td>address</td><td>3</td></tr></tbody></table></li><li><p>(1)第一条插入数据对应 IoTDB 时序为 root.monitor.student.A.B.C</p><p>(2)第二条插入数据对应 IoTDB 时序为 root.monitor.student.PH.PH.PH.D (其中PH表示占位符)。</p><p>需要注意的是,由于该条数据的 tag key=address 是第四个出现的,但是自身却没有对应的前三个 tag 值,因此需要用 PH 占位符来代替。这样做的目的是保证每条数据中的 tag 顺序不会乱,是符合当前顺序表中的顺序,从而查询数据的时候可以进行指定 tag 过滤。</p><p>(3)第三条插入数据对应 IoTDB 时序为 root.monitor.student.A.B.C.D</p><p>对应的 IoTDB 的实际存储为:</p></li></ol><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>+-----------------------------+--------------------------------+-------------------------------------+----------------------------------+ |
| | Time|root.monitor.student.A.B.C.score|root.monitor.student.PH.PH.PH.D.score|root.monitor.student.A.B.C.D.score| |
| +-----------------------------+--------------------------------+-------------------------------------+----------------------------------+ |
| |2021-10-12T01:21:26.907+08:00| 99| NULL| NULL| |
| |2021-10-12T01:21:27.310+08:00| NULL| 98| NULL| |
| |2021-10-12T01:21:27.313+08:00| NULL| NULL| 97| |
| +-----------------------------+--------------------------------+-------------------------------------+----------------------------------+ |
| </code></pre><div class="line-numbers" aria-hidden="true"><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><ol start="5"><li><p>如果上面三条数据插入的顺序不一样,我们可以看到对应的实际path路径也就发生了改变,因为InfluxDB数据中的Tag出现顺序发生了变化,所对应的到IoTDB中的path节点顺序也就发生了变化。</p><p>但是这样实际并不会影响查询的正确性,因为一旦Influxdb的Tag顺序确定之后,查询也会按照这个顺序表记录的顺序进行Tag值过滤。所以并不会影响查询的正确性。</p></li></ol><h5 id="_2-3-2-查询数据" tabindex="-1"><a class="header-anchor" href="#_2-3-2-查询数据" aria-hidden="true">#</a> 2.3.2 查询数据</h5><ol><li><p>查询student中phone=B的数据。在database=monitor,measurement=student中tag=phone的顺序为1,order最大值是3,对应到IoTDB的查询为:</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>monitor<span class="token punctuation">.</span>student<span class="token punctuation">.</span><span class="token operator">*</span><span class="token punctuation">.</span>B |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>查询student中phone=B且score>97的数据,对应到IoTDB的查询为:</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>monitor<span class="token punctuation">.</span>student<span class="token punctuation">.</span><span class="token operator">*</span><span class="token punctuation">.</span>B <span class="token keyword">where</span> score<span class="token operator">></span><span class="token number">97</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>查询student中phone=B且score>97且时间在最近七天内的的数据,对应到IoTDB的查询为:</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>monitor<span class="token punctuation">.</span>student<span class="token punctuation">.</span><span class="token operator">*</span><span class="token punctuation">.</span>B <span class="token keyword">where</span> score<span class="token operator">></span><span class="token number">97</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">></span> <span class="token function">now</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token operator">-</span><span class="token number">7</span>d |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>查询student中name=A或score>97,由于tag存储在路径中,因此没有办法用一次查询同时完成tag和field的<strong>或</strong>语义查询,因此需要多次查询进行或运算求并集,对应到IoTDB的查询为:</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>monitor<span class="token punctuation">.</span>student<span class="token punctuation">.</span>A |
| <span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>monitor<span class="token punctuation">.</span>student <span class="token keyword">where</span> score<span class="token operator">></span><span class="token number">97</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>最后手动对上面两次查询结果求并集。</p></li><li><p>查询student中(name=A或phone=B或sex=C)且score>97,由于tag存储在路径中,因此没有办法用一次查询完成tag的<strong>或</strong>语义, 因此需要多次查询进行或运算求并集,对应到IoTDB的查询为:</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>monitor<span class="token punctuation">.</span>student<span class="token punctuation">.</span>A <span class="token keyword">where</span> score<span class="token operator">></span><span class="token number">97</span> |
| <span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>monitor<span class="token punctuation">.</span>student<span class="token punctuation">.</span><span class="token operator">*</span><span class="token punctuation">.</span>B <span class="token keyword">where</span> score<span class="token operator">></span><span class="token number">97</span> |
| <span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>monitor<span class="token punctuation">.</span>student<span class="token punctuation">.</span><span class="token operator">*</span><span class="token punctuation">.</span><span class="token operator">*</span><span class="token punctuation">.</span>C <span class="token keyword">where</span> score<span class="token operator">></span><span class="token number">97</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>最后手动对上面三次查询结果求并集。</p></li></ol>`,55);function d(i,p){return n(),e("div",null,[t(` |
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| `),r])}const c=a(o,[["render",d],["__file","InfluxDB-Protocol.html.vue"]]);export{c as default}; |