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apache / iotdb-website / d028db3e826404479a87a25a9a5bc9e1889f883e / . / assets / js / 458.e369b8f9.js
blob: 4c0a8a99c8a04ac814c1a74e0b14ac6e3968f9bb [file] [log] [blame]
(window.webpackJsonp=window.webpackJsonp||[]).push([[458],{1022:function(t,e,v){"use strict";v.r(e);var _=v(68),l=Object(_.a)({},(function(){var t=this,e=t.$createElement,v=t._self._c||e;return v("ContentSlotsDistributor",{attrs:{"slot-key":t.$parent.slotKey}},[v("h1",{attrs:{id:"主要概念及术语"}},[v("a",{staticClass:"header-anchor",attrs:{href:"#主要概念及术语"}},[t._v("#")]),t._v(" 主要概念及术语")]),t._v(" "),v("p",[t._v("IoTDB中涉及如下基本概念：")]),t._v(" "),v("ul",[v("li",[t._v("设备")])]),t._v(" "),v("p",[t._v("设备指的是在实际场景中拥有传感器的装置。在IoTDB当中，所有的传感器都应有其对应的归属的设备。")]),t._v(" "),v("ul",[v("li",[t._v("传感器")])]),t._v(" "),v("p",[t._v("传感器是指在实际场景中的一种检测装置，它能感受到被测量的信息，并能将感受到的信息按一定规律变换成为电信号或其他所需形式的信息输出并发送给IoTDB。在IoTDB当中，存储的所有的数据及路径，都是以传感器为单位进行组织。")]),t._v(" "),v("ul",[v("li",[t._v("存储组")])]),t._v(" "),v("p",[t._v("用户可以将任意前缀路径设置成存储组。如有4条时间序列"),v("code",[t._v("root.vehicle.d1.s1")]),t._v(", "),v("code",[t._v("root.vehicle.d1.s2")]),t._v(", "),v("code",[t._v("root.vehicle.d2.s1")]),t._v(", "),v("code",[t._v("root.vehicle.d2.s2")]),t._v("，路径"),v("code",[t._v("root.vehicle")]),t._v("下的两个设备d1,d2可能属于同一个业主，或者同一个厂商，因此关系紧密。这时候就可以将前缀路径"),v("code",[t._v("root.vehicle")]),t._v("指定为一个存储组，这将使得IoTDB将其下的所有设备的数据存储在同一个文件夹下。未来"),v("code",[t._v("root.vehicle")]),t._v("下增加了新的设备，也将属于该存储组。")]),t._v(" "),v("blockquote",[v("p",[t._v("注意：不允许将一个完整路径(如上例的"),v("code",[t._v("root.vehicle.d1.s1")]),t._v(")设置成存储组。")])]),t._v(" "),v("p",[t._v("设置合理数量的存储组可以带来性能的提升：既不会因为产生过多的存储文件（夹）导致频繁切换IO降低系统速度（并且会占用大量内存且出现频繁的内存-文件切换），也不会因为过少的存储文件夹（降低了并发度从而）导致写入命令阻塞。")]),t._v(" "),v("p",[t._v("用户应根据自己的数据规模和使用场景，平衡存储文件的存储组设置，以达到更好的系统性能。（未来会有官方提供的存储组规模与性能测试报告）")]),t._v(" "),v("blockquote",[v("p",[t._v("注意：一个时间序列其前缀必须属于某个存储组。在创建时间序列之前，用户必须设定该序列属于哪个存储组（Storage Group）。只有设置了存储组的时间序列才可以被持久化在磁盘上。")])]),t._v(" "),v("p",[t._v("一个前缀路径一旦被设定成存储组后就不可以再更改这个存储组的设置。")]),t._v(" "),v("p",[t._v("一个存储组设定后，其对应的前缀路径的所有父层级与子层级也不允许再设置存储组（如，"),v("code",[t._v("root.ln")]),t._v("设置存储组后，root层级与"),v("code",[t._v("root.ln.wf01")]),t._v("不允许被设置为存储组）。")]),t._v(" "),v("ul",[v("li",[t._v("路径")])]),t._v(" "),v("p",[t._v("在IoTDB中，路径是指符合以下约束的表达式：")]),t._v(" "),v("div",{staticClass:"language- line-numbers-mode"},[v("pre",{pre:!0,attrs:{class:"language-text"}},[v("code",[t._v("path: LayerName (DOT LayerName)+\nLayerName: Identifier | STAR\n")])]),t._v(" "),v("div",{staticClass:"line-numbers-wrapper"},[v("span",{staticClass:"line-number"},[t._v("1")]),v("br"),v("span",{staticClass:"line-number"},[t._v("2")]),v("br")])]),v("p",[t._v("其中STAR为“*”，DOT为“.”。")]),t._v(" "),v("p",[t._v("我们称一个路径中在两个“.”中间的部分叫做一个层级，则"),v("code",[t._v("root.a.b.c")]),t._v("为一个层级为4的路径。")]),t._v(" "),v("p",[t._v("值得说明的是，在路径中，root为一个保留字符，它只允许出现在下文提到的时间序列的开头，若其他层级出现root，则无法解析，提示报错。")]),t._v(" "),v("ul",[v("li",[t._v("时间序列")])]),t._v(" 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