| import{_ as n,C as a,O as o,P as s,ah as r,Q as e,U as i,ai as l,ae as c,aW as h}from"./framework-62ad666a.js";const d={},u=h('<h2 id="压缩方式" tabindex="-1"><a class="header-anchor" href="#压缩方式" aria-hidden="true">#</a> 压缩方式</h2><p>当时间序列写入并按照指定的类型编码为二进制数据后,IoTDB 会使用压缩技术对该数据进行压缩,进一步提升空间存储效率。虽然编码和压缩都旨在提升存储效率,但编码技术通常只适合特定的数据类型(如二阶差分编码只适合与 INT32 或者 INT64 编码,存储浮点数需要先将他们乘以 10m 以转换为整数),然后将它们转换为二进制流。压缩方式(SNAPPY)针对二进制流进行压缩,因此压缩方式的使用不再受数据类型的限制。</p><h3 id="基本压缩方式" tabindex="-1"><a class="header-anchor" href="#基本压缩方式" aria-hidden="true">#</a> 基本压缩方式</h3><p>IoTDB 允许在创建一个时间序列的时候指定该列的压缩方式。现阶段 IoTDB 支持以下几种压缩方式:</p><ul><li>UNCOMPRESSED(不压缩)</li><li>SNAPPY 压缩</li><li>LZ4 压缩</li><li>GZIP 压缩</li><li>ZSTD 压缩</li><li>LZMA2 压缩</li></ul>',5),m=e("h3",{id:"压缩比统计信息",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#压缩比统计信息","aria-hidden":"true"},"#"),i(" 压缩比统计信息")],-1),_=e("p",{memtable_flush_time:""},"压缩比统计信息文件:data/system/compression_ratio/Ratio-{ratio_sum}-",-1),p=e("ul",null,[e("li",null,"ratio_sum: memtable压缩比的总和"),e("li",null,"memtable_flush_time: memtable刷盘的总次数")],-1),f=e("p",null,[i("通过 "),e("code",null,"ratio_sum / memtable_flush_time"),i(" 可以计算出平均压缩比")],-1);function S(N,b){const t=a("RouterLink");return o(),s("div",null,[r(` |
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| `),u,e("p",null,[i("压缩方式的指定语法详见本文 "),l(t,{to:"/zh/UserGuide/Master/Reference/SQL-Reference.html"},{default:c(()=>[i("SQL 参考文档")]),_:1}),i("。")]),m,_,p,f])}const L=n(d,[["render",S],["__file","Compression.html.vue"]]);export{L as default}; |