(window.webpackJsonp=window.webpackJsonp||[]).push([[286],{847:function(t,s,a){"use strict";a.r(s);var n=a(68),e=Object(n.a)({},(function(){var t=this,s=t.$createElement,a=t._self._c||s;return a("ContentSlotsDistributor",{attrs:{"slot-key":t.$parent.slotKey}},[a("h1",{attrs:{id:"按设备对齐查询"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#按设备对齐查询"}},[t._v("#")]),t._v(" 按设备对齐查询")]),t._v(" "),a("p",[t._v("AlignByDevicePlan 即按设备对齐查询对应的表结构为：")]),t._v(" "),a("table",[a("thead",[a("tr",[a("th",[t._v("Time")]),t._v(" "),a("th",[t._v("Device")]),t._v(" "),a("th",[t._v("sensor1")]),t._v(" "),a("th",[t._v("sensor2")]),t._v(" "),a("th",[t._v("sensor3")]),t._v(" "),a("th",[t._v("...")])])]),t._v(" "),a("tbody",[a("tr",[a("td"),t._v(" "),a("td"),t._v(" "),a("td"),t._v(" "),a("td"),t._v(" "),a("td"),t._v(" "),a("td")])])]),t._v(" "),a("h2",{attrs:{id:"设计原理"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#设计原理"}},[t._v("#")]),t._v(" 设计原理")]),t._v(" "),a("p",[t._v("按设备对齐查询其实现原理主要是计算出查询中每个设备对应的测点和过滤条件，然后将查询按设备分别进行，最后将结果集拼装并返回。")]),t._v(" "),a("h3",{attrs:{id:"alignbydeviceplan-中重要字段含义"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#alignbydeviceplan-中重要字段含义"}},[t._v("#")]),t._v(" AlignByDevicePlan 中重要字段含义")]),t._v(" "),a("p",[t._v("首先解释一下 AlignByDevicePlan 中一些重要字段的含义：")]),t._v(" "),a("ul",[a("li",[a("code",[t._v("List<String> measurements")]),t._v("：查询中出现的 measurement 列表。")]),t._v(" "),a("li",[a("code",[t._v("List<String> devices")]),t._v(": 由前缀路径得到的设备列表。")]),t._v(" "),a("li",[a("code",[t._v("Map<String, IExpression> deviceToFilterMap")]),t._v(": 用来存储设备对应的过滤条件。")]),t._v(" "),a("li",[a("code",[t._v("Map<String, TSDataType> measurementDataTypeMap")]),t._v("：该字段用于记录时间序列的实际数据类型，用于实际查询，其键值不包含聚合函数。")]),t._v(" "),a("li",[a("code",[t._v("Map<String, TSDataType> columnDataTypeMap")]),t._v("：该字段用来记录结果集中每列的数据类型，用于构造表头，输出结果集，可含有聚合函数。")]),t._v(" "),a("li",[a("code",[t._v("enum MeasurementType")]),t._v("：记录三种 measurement 类型。在任何设备中都不存在的 measurement 为 "),a("code",[t._v("NonExist")]),t._v(" 类型；有单引号或双引号的 measurement 为 "),a("code",[t._v("Constant")]),t._v(" 类型；存在的 measurement 为 "),a("code",[t._v("Exist")]),t._v(" 类型。")]),t._v(" "),a("li",[a("code",[t._v("Map<String, MeasurementType> measurementTypeMap")]),t._v(": 该字段用来记录查询中所有 measurement 的类型。")]),t._v(" "),a("li",[t._v("groupByTimePlan, fillQueryPlan, aggregationPlan：为了避免冗余，这三个执行计划被设定为 RawDataQueryPlan 的子类，而在 AlignByDevicePlan 中被设置为变量。如果查询计划属于这三个计划中的一种，则该字段会被赋值并保存。")])]),t._v(" "),a("p",[t._v("在进行具体实现过程的讲解前，先给出一个覆盖较为完整的例子，下面的解释过程中将结合该示例进行说明。")]),t._v(" "),a("div",{staticClass:"language-sql line-numbers-mode"},[a("pre",{pre:!0,attrs:{class:"language-sql"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("SELECT")]),t._v(" s1"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'1'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" 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number"}},[t._v("1")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("AND")]),t._v(" s1 "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("<")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("25")]),t._v(" ALIGN "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("BY")]),t._v(" DEVICE\n")])]),t._v(" "),a("div",{staticClass:"line-numbers-wrapper"},[a("span",{staticClass:"line-number"},[t._v("1")]),a("br")])]),a("p",[t._v("其中，系统中的时间序列为：")]),t._v(" "),a("ul",[a("li",[t._v("root.sg.d1.s1")]),t._v(" "),a("li",[t._v("root.sg.d1.s2")]),t._v(" "),a("li",[t._v("root.sg.d2.s1")])]),t._v(" "),a("p",[t._v("存储组 "),a("code",[t._v("root.sg")]),t._v(" 共包含两个设备 d1 和 d2，其中 d1 有两个传感器 s1 和 s2，d2 只有传感器 s1，相同传感器 s1 的数据类型相同。")]),t._v(" "),a("p",[t._v("下面将按具体过程进行分别解释：")]),t._v(" "),a("h3",{attrs:{id:"逻辑计划生成"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#逻辑计划生成"}},[t._v("#")]),t._v(" 逻辑计划生成")]),t._v(" "),a("ul",[a("li",[t._v("org.apache.iotdb.db.qp.Planner")])]),t._v(" "),a("p",[t._v("与原始数据查询不同，按设备对齐查询并不在此阶段进行 SELECT 语句和 WHERE 语句中后缀路径的拼接，而将在后续生成物理计划时，计算出每个设备对应的映射值和过滤条件。")]),t._v(" "),a("p",[t._v("因此，按设备对齐在此阶段所做的工作只包括对 WHERE 语句中过滤条件的优化。")]),t._v(" "),a("p",[t._v("对过滤条件的优化主要包括三部分：去非、转化析取范式、合并同路径过滤条件。对应的优化器分别为：RemoveNotOptimizer, DnfFilterOptimizer, MergeSingleFilterOptimizer。该部分逻辑可参考："),a("RouterLink",{attrs:{to:"/zh/SystemDesign/QueryEngine/Planner.html"}},[t._v("Planner")]),t._v(".")],1),t._v(" "),a("h3",{attrs:{id:"物理计划生成"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#物理计划生成"}},[t._v("#")]),t._v(" 物理计划生成")]),t._v(" "),a("ul",[a("li",[t._v("org.apache.iotdb.db.qp.strategy.PhysicalGenerator")])]),t._v(" "),a("p",[t._v("生成逻辑计划后，将调用 PhysicalGenerator 类中的 "),a("code",[t._v("transformToPhysicalPlan()")]),t._v(" 方法将该逻辑计划转化为物理计划。对于按设备对齐查询，该方法的主要逻辑实现在 "),a("code",[t._v("transformQuery()")]),t._v(" 方法中。")]),t._v(" "),a("p",[a("strong",[t._v("该阶段所做的主要工作为生成查询对应的")]),t._v(" "),a("code",[t._v("AlignByDevicePlan")]),t._v("，"),a("strong",[t._v("填充其中的变量信息。")])]),t._v(" "),a("p",[t._v("其主要将 SELECT 语句中得到的后缀路径与 FROM 子句中的前缀路径进行拼接，从而计算出查询的 Measurement 及其类型、数据类型，计算流程如下：")]),t._v(" "),a("div",{staticClass:"language-java line-numbers-mode"},[a("pre",{pre:!0,attrs:{class:"language-java"}},[a("code",[t._v("  "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 首先遍历后缀路径")]),t._v("\n  "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("for")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("int")]),t._v(" i "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" i "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("<")]),t._v(" suffixPaths"),a("span",{pre:!0,attrs:{class:"token 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中的实际查询")]),t._v("\n        "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),t._v(" aggregation "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v("\n            originAggregations "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("!=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("null")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("&&")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("!")]),t._v("originAggregations"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("isEmpty")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n                "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("?")]),t._v(" originAggregations"),a("span",{pre:!0,attrs:{class:"token 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"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 检查同名传感器的数据类型一致性")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),t._v(" measurementChecked"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("TSDataType")]),t._v(" columnDataType "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" columnDataTypes"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("get")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("pathIdx"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 如果有同名传感器则进行数据类型比较")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("columnDataTypeMap"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("containsKey")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("measurementChecked"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n            "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 数据类型不一致则抛出异常，结束")]),t._v("\n            "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token 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"),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("QueryProcessException")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n            "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("else")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n            "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 当前没有该 Measurement 则进行记录")]),t._v("\n            "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n          "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 进行到这一步说明该 Measurement 在该设备下存在且正确，")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 首先更新 measurementSetOfGivenSuffix，重复则不可再加入")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 其次如果该 measurement 之前其被识别为 NonExist类型，则将其更新为 Exist")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("measurementSetOfGivenSuffix"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),a("span",{pre:!0,attrs:{class:"token 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measurementTypeMap"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("put")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("measurementChecked"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("MeasurementType")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Exist")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n        "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n          "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 更新 paths")]),t._v("\n          paths"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("path"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n      "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("catch")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("MetadataException")]),t._v(" e"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n        "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("throw")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LogicalOptimizeException")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n      "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 更新 measurements")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 注意在一个后缀路径的循环内部，使用了 set 避免重复的 measurement")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 而在循环外部使用了 List 来保证输出包含用户输入的所有 measurements")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 示例中，对于后缀 *, measurementSetOfGivenSuffix = {s1,s2}")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 对于后缀 s1, measurementSetOfGivenSuffix = {s1}")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 因此最终 measurements 为 [s1,s2,s1].")]),t._v("\n    measurements"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("addAll")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("measurementSetOfGivenSuffix"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n  "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n")])]),t._v(" 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"),a("p",[a("code",[t._v("concatFilterPath()")]),t._v(" 方法遍历未拼接的 FilterOperator 二叉树，判断节点是否为叶子节点，如果是，则取该叶子结点的路径，如果路径以 time 或 root 开头则不做处理，否则将设备名与节点路径进行拼接后返回；如果不是，则对该节点的所有子节点进行迭代处理。")]),t._v(" "),a("p",[t._v("示例中，设备1过滤条件拼接后的结果为 "),a("code",[t._v("time = 1 AND root.sg.d1.s1 < 25")]),t._v("，设备2为 "),a("code",[t._v("time = 1 AND root.sg.d2.s1 < 25")]),t._v("。")]),t._v(" "),a("p",[t._v("下面用示例总结一下通过该阶段计算得到的变量信息：")]),t._v(" "),a("ul",[a("li",[t._v("measurement 列表 "),a("code",[t._v("measurements")]),t._v("："),a("code",[t._v("[s1, '1', s1, s2, s2, s5]")])]),t._v(" "),a("li",[t._v("measurement 类型 "),a("code",[t._v("measurementTypeMap")]),t._v("：\n"),a("ul",[a("li",[a("code",[t._v("s1 -> Exist")])]),t._v(" "),a("li",[a("code",[t._v("s2 -> Exist")])]),t._v(" "),a("li",[a("code",[t._v("'1' -> Constant")])]),t._v(" "),a("li",[a("code",[t._v("s5 -> NonExist")])])])]),t._v(" "),a("li",[t._v("每个设备的过滤条件 "),a("code",[t._v("deviceToFilterMap")]),t._v("：\n"),a("ul",[a("li",[a("code",[t._v("root.sg.d1 -> time = 1 AND root.sg.d1.s1 < 25")])]),t._v(" "),a("li",[a("code",[t._v("root.sg.d2 -> time = 1 AND root.sg.d2.s1 < 25")])])])])]),t._v(" "),a("h3",{attrs:{id:"构造表头-columnheader"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#构造表头-columnheader"}},[t._v("#")]),t._v(" 构造表头 (ColumnHeader)")]),t._v(" "),a("ul",[a("li",[t._v("org.apache.iotdb.db.service.TSServiceImpl")])]),t._v(" "),a("p",[t._v("在生成物理计划后，则可以执行 TSServiceImpl 中的 executeQueryStatement() 方法生成结果集并返回，其中第一步是构造表头。")]),t._v(" "),a("p",[t._v("按设备对齐查询在调用 "),a("code",[t._v("TSServiceImpl.getQueryColumnHeaders()")]),t._v(" 方法后，根据查询类型进入 "),a("code",[t._v("TSServiceImpl.getAlignByDeviceQueryHeaders()")]),t._v(" 来构造表头。")]),t._v(" "),a("p",[a("code",[t._v("getAlignByDeviceQueryHeaders()")]),t._v(" 方法声明如下：")]),t._v(" "),a("div",{staticClass:"language-java line-numbers-mode"},[a("pre",{pre:!0,attrs:{class:"language-java"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("private")]),t._v(" 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