| (window.webpackJsonp=window.webpackJsonp||[]).push([[296],{863:function(s,a,t){"use strict";t.r(a);var n=t(69),e=Object(n.a)({},(function(){var s=this,a=s.$createElement,t=s._self._c||a;return t("ContentSlotsDistributor",{attrs:{"slot-key":s.$parent.slotKey}},[t("h1",{attrs:{id:"按时间倒序查询"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#按时间倒序查询"}},[s._v("#")]),s._v(" 按时间倒序查询")]),s._v(" "),t("h2",{attrs:{id:"实现原理"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#实现原理"}},[s._v("#")]),s._v(" 实现原理")]),s._v(" "),t("p",[s._v("倒序分为 3 个维度来实现，由内核层到用户层分别为: "),t("code",[s._v("TsFile")]),s._v("、"),t("code",[s._v("BatchData")]),s._v("、"),t("code",[s._v("数据集")]),s._v(".")]),s._v(" "),t("ol",[t("li",[t("code",[s._v("TsFile")]),s._v(" 是用来存储所有原始数据的文件格式，在存储时分为 "),t("code",[s._v("顺序文件")]),s._v(" 和 "),t("code",[s._v("乱序文件")]),s._v(".\n"),t("code",[s._v("ChunkData")]),s._v(" 是 "),t("code",[s._v("TsFile")]),s._v(" 中的基本数据块，保存了具体某一个测点的数据，且"),t("strong",[s._v("数据是按照时间升序存储的")]),s._v(".")]),s._v(" "),t("li",[t("code",[s._v("BatchData")]),s._v(" 是基础数据交换结构，无论是从文件系统还是缓存读出的数据都会被转换成 "),t("code",[s._v("BatchData")]),s._v(" 结构.")]),s._v(" "),t("li",[t("code",[s._v("数据集")]),s._v(" 是封装根据用户输入的 "),t("code",[s._v("SQL")]),s._v(" 语句的结果集格式，转换和封装 "),t("code",[s._v("BatchData")]),s._v(" 中的数据。")])]),s._v(" "),t("p",[s._v("实际系统需要考虑的方面会更多，但主要为以上 3 点。\n下面分别介绍各个层面如何实现基于时间的倒序查询:")]),s._v(" "),t("h2",{attrs:{id:"tsfile"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#tsfile"}},[s._v("#")]),s._v(" TsFile")]),s._v(" "),t("p",[s._v("1."),t("code",[s._v("TsFile")]),s._v(" 在文件末尾存储了各个测点在文件中的最小时间(开始时间)和最大时间(结束时间)，\n所以当我们按照开始时间升序排列文件并读取数据时,是升序读取;当使用结束时间倒序排列文件\n("),t("strong",[s._v("顺序文件也可以使用开始时间倒序排列")]),s._v(")并读取数据时,是"),t("strong",[s._v("伪倒序读取")]),s._v("(因为文件内依然是升序存储的),数据示例:")]),s._v(" "),t("div",{staticClass:"language- line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-text"}},[t("code",[s._v(" 按照开始时间升序排列 (1,6)\n +---TsFile1---+ +---TsFile2---+ \n | 1,2,3,4,5 | | 6,7,8,9,10 |\n +-------------+ +-------------+\n \n 按照结束降序排列 (10,5)\n +---TsFile2---+ +---TsFile1---+ \n | 6,7,8,9,10 | | 1,2,3,4,5 |\n +-------------+ +-------------+ \n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br")])]),t("p",[s._v("2.上面的示例只描述了顺序文件，乱序文件的特点是: 文件中存储的数据与其他文件的数据存在相交，\n不仅仅和顺序文件相交，乱序和乱序文件之间也可能相交。")]),s._v(" "),t("div",{staticClass:"language- line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-text"}},[t("code",[s._v(" +---TsFile1---+ +---TsFile2---+ \n | 1,2,3,4,5 | | 6,7,8,9,10 |\n +-------------+ +-------------+\n +--------------unseq1-----------+ \n | 2,11 | \n +-------------------------------+\n +-unseq2-+ \n | 3,4,5 | \n +--------+\n \n")])]),s._v(" 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isDelete"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\n "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("//对于所有文件层的临时缓存排序规则的实现")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token generics"}},[t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("<")]),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("T")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(">")])]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Comparator")]),t("span",{pre:!0,attrs:{class:"token generics"}},[t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("<")]),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("T")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(">")])]),s._v(" "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("comparingLong")]),t("span",{pre:!0,attrs:{class:"token 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punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("long")]),s._v(" time"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("long")]),s._v(" endpointTime"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\n "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("//或许当前使用的排序方式")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("boolean")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("getAscending")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br"),t("span",{staticClass:"line-number"},[s._v("10")]),t("br"),t("span",{staticClass:"line-number"},[s._v("11")]),t("br"),t("span",{staticClass:"line-number"},[s._v("12")]),t("br"),t("span",{staticClass:"line-number"},[s._v("13")]),t("br"),t("span",{staticClass:"line-number"},[s._v("14")]),t("br"),t("span",{staticClass:"line-number"},[s._v("15")]),t("br"),t("span",{staticClass:"line-number"},[s._v("16")]),t("br"),t("span",{staticClass:"line-number"},[s._v("17")]),t("br"),t("span",{staticClass:"line-number"},[s._v("18")]),t("br"),t("span",{staticClass:"line-number"},[s._v("19")]),t("br"),t("span",{staticClass:"line-number"},[s._v("20")]),t("br"),t("span",{staticClass:"line-number"},[s._v("21")]),t("br"),t("span",{staticClass:"line-number"},[s._v("22")]),t("br"),t("span",{staticClass:"line-number"},[s._v("23")]),t("br"),t("span",{staticClass:"line-number"},[s._v("24")]),t("br"),t("span",{staticClass:"line-number"},[s._v("25")]),t("br"),t("span",{staticClass:"line-number"},[s._v("26")]),t("br")])]),t("p",[s._v("5.完成了上述步骤，倒序取出来的数据如下：")]),s._v(" "),t("div",{staticClass:"language- line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-text"}},[t("code",[s._v("6,7,8,9,10,1,2,3,4,5\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("这是因为数据在Chunk、Page、缓存中都是升序存储，所以转移到 "),t("code",[s._v("BatchData")]),s._v(" 中查看就是示例中的样子。")]),s._v(" "),t("h2",{attrs:{id:"batchdata"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#batchdata"}},[s._v("#")]),s._v(" BatchData")]),s._v(" "),t("p",[s._v("1.为了兼容原有的文件读取数据方式，所以在数据放到 "),t("code",[s._v("BatchData")]),s._v(" 之后倒序读取集合里的数据就可以得到最终结果。")]),s._v(" "),t("p",[s._v("BatchData类似一个二维数组的格式，封装了写入和读取的方法，对于倒序，抽象了下面的子类：")]),s._v(" "),t("div",{staticClass:"language-java line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-java"}},[t("code",[s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("public")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("class")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("DescBatchData")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("extends")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("BatchData")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("//判断是否还有值，正序时候判断是否读到写入的size位置，倒序就是判断是否读到了0的位置")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("public")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("boolean")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("hasCurrent")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("//指针移动到下一个数据，正序为 index+1 操作， 倒序为 index-1 操作")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("public")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("void")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("next")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("//重制指针位置，正序为重制到0，倒序重制到数据写入位置")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("public")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("void")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("resetBatchData")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token 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time"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),s._v("\n")])]),s._v(" 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"),t("p",[s._v("3.因为"),t("code",[s._v("MergeReader")]),s._v("使用了"),t("code",[s._v("PageReader")]),s._v("，所以在降序模式的时候数据会被倒序读出来(如下):")]),s._v(" "),t("div",{staticClass:"language- line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-text"}},[t("code",[s._v("5 4 3 2 1 \n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("这种情况会使得"),t("code",[s._v("BatchData")]),s._v("使用"),t("code",[s._v("getValueInTimestamp")]),s._v("方法变得困难(因为在正序模式的时候默认为越往后的数据时间越大，\n倒序模式的时候越后时间越小)，但是按照如上数据示例无论在哪种模式下，都是违反了期望的数据时间比较，所以，新增了一个\n"),t("code",[s._v("getValueInTimestamp(long time, BiFunction<Long, Long, Boolean> compare)")]),s._v("方法，\n让不同的使用场景抉择基于时间的数据查找方式。")]),s._v(" "),t("p",[s._v("4.至此数据从磁盘和缓存中取出的数据都是严格按照时间排序的了。")]),s._v(" "),t("h2",{attrs:{id:"数据集"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#数据集"}},[s._v("#")]),s._v(" 数据集")]),s._v(" "),t("p",[s._v("1.原始数据查询")]),s._v(" "),t("div",{staticClass:"language-sql 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"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(">")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("100")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("order")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("by")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("time")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("desc")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br")])]),t("p",[s._v("原始数据查询中，只要向"),t("code",[s._v("SeriesReader")]),s._v("传递了正确的ascending参数就能得到正确的结果。")]),s._v(" "),t("p",[s._v("2.GroupBy")]),s._v(" "),t("div",{staticClass:"language-sql line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-sql"}},[t("code",[t("span",{pre:!0,attrs:{class:"token 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"),t("p",[s._v("对于降序查询，因为数据在倒序遍历，并不知道它的前值是多少，所以为 "),t("code",[s._v("GroupByEngineDataSet")]),s._v("\n抽象了 "),t("code",[s._v("peekNextNotNullValue")]),s._v(" 方法，继续往前执行，一直查找到一个不为空的值返回。并将该值缓存到\n"),t("code",[s._v("GroupByFillDataSet")]),s._v(" 中并遵从升序的补值方法，到当前的循环开始时间小于缓存的时间时缓存失效。")]),s._v(" "),t("p",[s._v("4.Last\n在"),t("code",[s._v("LastQueryExecutor")]),s._v("中，一次性将所有的结果集封装在了一个List中，\n当倒序时将List中的数据根据时间进行一次排序,就得到了结果,详情见"),t("code",[s._v("ListDataSet")]),s._v(".")])])}),[],!1,null,null,null);a.default=e.exports}}]); |