<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <title> </title>
    <meta name="generator" content="VuePress 1.8.2">
    <link rel="icon" href="/favicon.ico">
    <meta name="description" content=" ">
    <meta name="Description" content="Apache IoTDB: Time Series Database for IoT">
    <meta name="Keywords" content="TSDB, time series, time series database, IoTDB, IoT database, IoT data management,时序数据库, 时间序列管理, IoTDB, 物联网数据库, 实时数据库, 物联网数据管理, 物联网数据">
    <meta name="baidu-site-verification" content="wfKETzB3OT">
    <meta name="google-site-verification" content="mZWAoRY0yj_HAr-s47zHCGHzx5Ju-RVm5wDbPnwQYFo">
    
    <link rel="preload" href="/assets/css/0.styles.c79f5191.css" as="style"><link rel="preload" href="/assets/js/app.35ba4ac3.js" as="script"><link rel="preload" href="/assets/js/3.96a076a8.js" as="script"><link rel="preload" href="/assets/js/4.a65360c5.js" as="script"><link rel="preload" href="/assets/js/353.d21f105a.js" as="script"><link rel="prefetch" href="/assets/js/10.60470782.js"><link rel="prefetch" href="/assets/js/100.e2b000a0.js"><link rel="prefetch" href="/assets/js/101.e8ddf551.js"><link rel="prefetch" href="/assets/js/102.8e4c98f5.js"><link rel="prefetch" href="/assets/js/103.ca950be9.js"><link rel="prefetch" href="/assets/js/104.5105e29f.js"><link rel="prefetch" href="/assets/js/105.6dc4fd1d.js"><link rel="prefetch" href="/assets/js/106.8902c844.js"><link rel="prefetch" href="/assets/js/107.9f4a26e9.js"><link rel="prefetch" href="/assets/js/108.fa211ff9.js"><link rel="prefetch" href="/assets/js/109.26ee1ad0.js"><link rel="prefetch" href="/assets/js/11.e6c21699.js"><link rel="prefetch" href="/assets/js/110.a5668c48.js"><link rel="prefetch" href="/assets/js/111.0b78727f.js"><link rel="prefetch" href="/assets/js/112.1f92e6d5.js"><link rel="prefetch" href="/assets/js/113.76c7aecf.js"><link rel="prefetch" href="/assets/js/114.bf1fe841.js"><link rel="prefetch" href="/assets/js/115.528cda1d.js"><link rel="prefetch" href="/assets/js/116.763ead1d.js"><link rel="prefetch" href="/assets/js/117.34441361.js"><link rel="prefetch" href="/assets/js/118.c2814fb8.js"><link rel="prefetch" href="/assets/js/119.666d003a.js"><link rel="prefetch" href="/assets/js/12.26a10771.js"><link rel="prefetch" href="/assets/js/120.6689ad59.js"><link rel="prefetch" href="/assets/js/121.e260fdd5.js"><link rel="prefetch" href="/assets/js/122.f28db74f.js"><link rel="prefetch" href="/assets/js/123.5e201f75.js"><link rel="prefetch" href="/assets/js/124.806d3ac7.js"><link rel="prefetch" href="/assets/js/125.670b8f46.js"><link rel="prefetch" href="/assets/js/126.fb3144a4.js"><link rel="prefetch" href="/assets/js/127.484bbf5c.js"><link rel="prefetch" href="/assets/js/128.c8b4957e.js"><link rel="prefetch" href="/assets/js/129.7814849a.js"><link rel="prefetch" href="/assets/js/13.cd64146f.js"><link rel="prefetch" href="/assets/js/130.02825d29.js"><link rel="prefetch" href="/assets/js/131.0e736cb4.js"><link rel="prefetch" href="/assets/js/132.038f09a6.js"><link rel="prefetch" href="/assets/js/133.1c3d1d7b.js"><link rel="prefetch" href="/assets/js/134.5ed1f677.js"><link rel="prefetch" href="/assets/js/135.3f17944b.js"><link rel="prefetch" href="/assets/js/136.b509f0f5.js"><link rel="prefetch" href="/assets/js/137.5b22ea8d.js"><link rel="prefetch" href="/assets/js/138.98781e3d.js"><link rel="prefetch" href="/assets/js/139.cc2652f5.js"><link rel="prefetch" href="/assets/js/14.f8f59c2a.js"><link rel="prefetch" href="/assets/js/140.9784e496.js"><link rel="prefetch" href="/assets/js/141.2a2995df.js"><link rel="prefetch" href="/assets/js/142.e405ba9a.js"><link rel="prefetch" href="/assets/js/143.2ab64035.js"><link rel="prefetch" href="/assets/js/144.2ac58e57.js"><link rel="prefetch" href="/assets/js/145.acdd536b.js"><link rel="prefetch" href="/assets/js/146.27cf4253.js"><link rel="prefetch" href="/assets/js/147.70d32693.js"><link rel="prefetch" href="/assets/js/148.a443b591.js"><link rel="prefetch" href="/assets/js/149.1924fec7.js"><link rel="prefetch" href="/assets/js/15.0e7120ba.js"><link rel="prefetch" href="/assets/js/150.c162962f.js"><link rel="prefetch" href="/assets/js/151.82faca10.js"><link rel="prefetch" href="/assets/js/152.89c5a57f.js"><link rel="prefetch" href="/assets/js/153.8a9aeb20.js"><link rel="prefetch" href="/assets/js/154.eefdf29e.js"><link rel="prefetch" href="/assets/js/155.96e814c9.js"><link rel="prefetch" href="/assets/js/156.eaef02df.js"><link rel="prefetch" href="/assets/js/157.f13427a7.js"><link rel="prefetch" href="/assets/js/158.c2f9ec68.js"><link rel="prefetch" href="/assets/js/159.cb59b892.js"><link rel="prefetch" href="/assets/js/16.22ec18ce.js"><link rel="prefetch" href="/assets/js/160.f1bba785.js"><link rel="prefetch" href="/assets/js/161.6ba35dd2.js"><link rel="prefetch" href="/assets/js/162.64aec67d.js"><link rel="prefetch" href="/assets/js/163.ac66ae3c.js"><link rel="prefetch" href="/assets/js/164.75db10d4.js"><link rel="prefetch" href="/assets/js/165.ffed9d3c.js"><link rel="prefetch" href="/assets/js/166.292068cd.js"><link rel="prefetch" href="/assets/js/167.b8f0f092.js"><link rel="prefetch" href="/assets/js/168.a2b08bc6.js"><link rel="prefetch" href="/assets/js/169.894010e8.js"><link rel="prefetch" href="/assets/js/17.d134c9d8.js"><link rel="prefetch" href="/assets/js/170.851fd688.js"><link rel="prefetch" href="/assets/js/171.bee60f85.js"><link rel="prefetch" href="/assets/js/172.17301909.js"><link rel="prefetch" href="/assets/js/173.95e440e2.js"><link rel="prefetch" href="/assets/js/174.d1c66edd.js"><link rel="prefetch" href="/assets/js/175.e54e4061.js"><link rel="prefetch" href="/assets/js/176.b01610c1.js"><link rel="prefetch" href="/assets/js/177.6602f657.js"><link rel="prefetch" href="/assets/js/178.506e9107.js"><link rel="prefetch" href="/assets/js/179.6792a8f0.js"><link rel="prefetch" href="/assets/js/18.e640e522.js"><link rel="prefetch" href="/assets/js/180.7d058689.js"><link rel="prefetch" href="/assets/js/181.52afb246.js"><link rel="prefetch" href="/assets/js/182.af025d86.js"><link rel="prefetch" href="/assets/js/183.718514b3.js"><link rel="prefetch" href="/assets/js/184.2f135dd7.js"><link rel="prefetch" href="/assets/js/185.c750908d.js"><link rel="prefetch" href="/assets/js/186.4c87c04d.js"><link rel="prefetch" href="/assets/js/187.b3780896.js"><link rel="prefetch" href="/assets/js/188.1a21c282.js"><link rel="prefetch" href="/assets/js/189.9acf8d5c.js"><link rel="prefetch" href="/assets/js/19.554dfad4.js"><link rel="prefetch" href="/assets/js/190.cc0cd7d1.js"><link rel="prefetch" href="/assets/js/191.896a7149.js"><link rel="prefetch" href="/assets/js/192.997b6697.js"><link rel="prefetch" href="/assets/js/193.edfcc324.js"><link rel="prefetch" href="/assets/js/194.f7e5dfff.js"><link rel="prefetch" href="/assets/js/195.b31e7d30.js"><link rel="prefetch" href="/assets/js/196.86bc78cf.js"><link rel="prefetch" href="/assets/js/197.cd9b0c3a.js"><link rel="prefetch" href="/assets/js/198.ed57f725.js"><link rel="prefetch" href="/assets/js/199.9610c044.js"><link rel="prefetch" href="/assets/js/20.4b3311fd.js"><link rel="prefetch" href="/assets/js/200.6d6ccdae.js"><link rel="prefetch" href="/assets/js/201.b6446c8f.js"><link rel="prefetch" href="/assets/js/202.7491b7cb.js"><link rel="prefetch" href="/assets/js/203.f882b31f.js"><link rel="prefetch" href="/assets/js/204.a435a4df.js"><link rel="prefetch" href="/assets/js/205.11f449c5.js"><link rel="prefetch" href="/assets/js/206.52b86e55.js"><link rel="prefetch" href="/assets/js/207.365abb89.js"><link rel="prefetch" href="/assets/js/208.edd5ba13.js"><link rel="prefetch" href="/assets/js/209.7537428f.js"><link rel="prefetch" href="/assets/js/21.c90f33d7.js"><link rel="prefetch" href="/assets/js/210.36aa5018.js"><link rel="prefetch" href="/assets/js/211.a657351a.js"><link rel="prefetch" href="/assets/js/212.2a8a092d.js"><link rel="prefetch" href="/assets/js/213.4a904163.js"><link rel="prefetch" href="/assets/js/214.20fc09c1.js"><link rel="prefetch" href="/assets/js/215.dd0baa0c.js"><link rel="prefetch" href="/assets/js/216.0898f799.js"><link rel="prefetch" href="/assets/js/217.65cf1eba.js"><link rel="prefetch" href="/assets/js/218.aba2c019.js"><link rel="prefetch" href="/assets/js/219.ff1353e7.js"><link rel="prefetch" href="/assets/js/22.7a1f06fe.js"><link rel="prefetch" href="/assets/js/220.ed26afb4.js"><link rel="prefetch" href="/assets/js/221.2dbabfdd.js"><link rel="prefetch" href="/assets/js/222.307bdc05.js"><link rel="prefetch" href="/assets/js/223.e0731710.js"><link rel="prefetch" href="/assets/js/224.ac831490.js"><link rel="prefetch" href="/assets/js/225.a9797599.js"><link rel="prefetch" href="/assets/js/226.85a77987.js"><link rel="prefetch" href="/assets/js/227.6273e947.js"><link rel="prefetch" href="/assets/js/228.9cf4477d.js"><link rel="prefetch" href="/assets/js/229.ad7b2a28.js"><link rel="prefetch" href="/assets/js/23.bce95595.js"><link rel="prefetch" href="/assets/js/230.276e0251.js"><link rel="prefetch" href="/assets/js/231.3db2a0fa.js"><link rel="prefetch" href="/assets/js/232.b4bd9a55.js"><link rel="prefetch" href="/assets/js/233.53776299.js"><link rel="prefetch" href="/assets/js/234.05ad11c6.js"><link rel="prefetch" href="/assets/js/235.98e38acf.js"><link rel="prefetch" href="/assets/js/236.d975a1d2.js"><link rel="prefetch" href="/assets/js/237.de4279d3.js"><link rel="prefetch" href="/assets/js/238.f4594499.js"><link rel="prefetch" href="/assets/js/239.e8fd0643.js"><link rel="prefetch" href="/assets/js/24.887866cf.js"><link rel="prefetch" href="/assets/js/240.105e2a7c.js"><link rel="prefetch" href="/assets/js/241.4b5f2bee.js"><link rel="prefetch" href="/assets/js/242.f25a0ad8.js"><link rel="prefetch" href="/assets/js/243.0d5e5ae8.js"><link rel="prefetch" href="/assets/js/244.355a7c6d.js"><link rel="prefetch" href="/assets/js/245.e2747a0f.js"><link rel="prefetch" href="/assets/js/246.4814cde5.js"><link rel="prefetch" href="/assets/js/247.41684524.js"><link rel="prefetch" href="/assets/js/248.536526ef.js"><link rel="prefetch" href="/assets/js/249.35b26de1.js"><link rel="prefetch" href="/assets/js/25.957ff41a.js"><link rel="prefetch" href="/assets/js/250.99cdec3c.js"><link rel="prefetch" href="/assets/js/251.605292d5.js"><link rel="prefetch" href="/assets/js/252.d05db63c.js"><link rel="prefetch" href="/assets/js/253.8c041ed8.js"><link rel="prefetch" href="/assets/js/254.c03b32fe.js"><link rel="prefetch" href="/assets/js/255.0002399b.js"><link rel="prefetch" href="/assets/js/256.972cf088.js"><link rel="prefetch" href="/assets/js/257.5f5e6d0e.js"><link rel="prefetch" href="/assets/js/258.e0a5fdc0.js"><link rel="prefetch" href="/assets/js/259.9b4e9ad2.js"><link rel="prefetch" href="/assets/js/26.c8060b33.js"><link rel="prefetch" href="/assets/js/260.8fc4798b.js"><link rel="prefetch" href="/assets/js/261.b7fa504b.js"><link rel="prefetch" href="/assets/js/262.c1e05910.js"><link rel="prefetch" href="/assets/js/263.3d18dc63.js"><link rel="prefetch" href="/assets/js/264.8a2db8a2.js"><link rel="prefetch" href="/assets/js/265.94d31290.js"><link rel="prefetch" href="/assets/js/266.59db673f.js"><link rel="prefetch" href="/assets/js/267.015dfed5.js"><link rel="prefetch" href="/assets/js/268.f70f6b44.js"><link rel="prefetch" href="/assets/js/269.672a997b.js"><link rel="prefetch" href="/assets/js/27.2476b973.js"><link rel="prefetch" href="/assets/js/270.e5ee9893.js"><link rel="prefetch" href="/assets/js/271.c297d886.js"><link rel="prefetch" href="/assets/js/272.82f549fa.js"><link rel="prefetch" href="/assets/js/273.5c88635e.js"><link rel="prefetch" href="/assets/js/274.a7f437ff.js"><link rel="prefetch" href="/assets/js/275.76da86b8.js"><link rel="prefetch" href="/assets/js/276.1e3ac385.js"><link rel="prefetch" href="/assets/js/277.ca8fea07.js"><link rel="prefetch" href="/assets/js/278.a86fb436.js"><link rel="prefetch" href="/assets/js/279.d84dba71.js"><link rel="prefetch" href="/assets/js/28.112d911e.js"><link rel="prefetch" href="/assets/js/280.c56e2c2b.js"><link rel="prefetch" href="/assets/js/281.6a5183bc.js"><link rel="prefetch" href="/assets/js/282.4ee881f8.js"><link rel="prefetch" href="/assets/js/283.ed1f376b.js"><link rel="prefetch" href="/assets/js/284.7f612c82.js"><link rel="prefetch" href="/assets/js/285.9512cabe.js"><link rel="prefetch" href="/assets/js/286.25f46725.js"><link rel="prefetch" href="/assets/js/287.32ab5626.js"><link rel="prefetch" href="/assets/js/288.16a3e78c.js"><link rel="prefetch" href="/assets/js/289.3a9ad6c5.js"><link rel="prefetch" href="/assets/js/29.430f946b.js"><link rel="prefetch" href="/assets/js/290.66371c9f.js"><link rel="prefetch" href="/assets/js/291.bb1fd8ca.js"><link rel="prefetch" href="/assets/js/292.16654a32.js"><link rel="prefetch" href="/assets/js/293.bc5f2edd.js"><link rel="prefetch" href="/assets/js/294.0b4534d4.js"><link rel="prefetch" href="/assets/js/295.3fdee573.js"><link rel="prefetch" href="/assets/js/296.ba646b1b.js"><link rel="prefetch" href="/assets/js/297.4fc8c2fc.js"><link rel="prefetch" href="/assets/js/298.24de5e87.js"><link rel="prefetch" href="/assets/js/299.983179df.js"><link rel="prefetch" href="/assets/js/30.d46382c7.js"><link rel="prefetch" href="/assets/js/300.f247dc2a.js"><link rel="prefetch" href="/assets/js/301.fa3fd2b2.js"><link rel="prefetch" href="/assets/js/302.bb1de367.js"><link rel="prefetch" href="/assets/js/303.cd1328f2.js"><link rel="prefetch" href="/assets/js/304.0494314e.js"><link rel="prefetch" href="/assets/js/305.38cd6f26.js"><link rel="prefetch" href="/assets/js/306.55e7ead5.js"><link rel="prefetch" href="/assets/js/307.bd167747.js"><link rel="prefetch" href="/assets/js/308.b859ed93.js"><link rel="prefetch" href="/assets/js/309.335f24b7.js"><link rel="prefetch" href="/assets/js/31.e244252e.js"><link rel="prefetch" href="/assets/js/310.934b0a33.js"><link rel="prefetch" href="/assets/js/311.85a79804.js"><link rel="prefetch" href="/assets/js/312.c0f6001e.js"><link rel="prefetch" href="/assets/js/313.70ba3f4b.js"><link rel="prefetch" href="/assets/js/314.534a4be1.js"><link rel="prefetch" href="/assets/js/315.ed1bc2f6.js"><link rel="prefetch" href="/assets/js/316.38c211b1.js"><link rel="prefetch" href="/assets/js/317.b03ba6d9.js"><link rel="prefetch" href="/assets/js/318.6e795d26.js"><link rel="prefetch" href="/assets/js/319.03c7f58c.js"><link rel="prefetch" href="/assets/js/32.d905c2cd.js"><link rel="prefetch" href="/assets/js/320.c5e3d1f3.js"><link rel="prefetch" href="/assets/js/321.022baf3d.js"><link rel="prefetch" href="/assets/js/322.e0c8d7ab.js"><link rel="prefetch" href="/assets/js/323.d5f6e667.js"><link rel="prefetch" href="/assets/js/324.ca18024b.js"><link rel="prefetch" href="/assets/js/325.39192cbd.js"><link rel="prefetch" href="/assets/js/326.29f462df.js"><link rel="prefetch" href="/assets/js/327.72807cb6.js"><link rel="prefetch" href="/assets/js/328.c7edebfc.js"><link rel="prefetch" href="/assets/js/329.9ca35978.js"><link rel="prefetch" href="/assets/js/33.a34a1c24.js"><link rel="prefetch" href="/assets/js/330.57eaedf7.js"><link rel="prefetch" href="/assets/js/331.059af8f9.js"><link rel="prefetch" href="/assets/js/332.6cc91623.js"><link rel="prefetch" href="/assets/js/333.0fcbafb4.js"><link rel="prefetch" href="/assets/js/334.b4dd2028.js"><link rel="prefetch" href="/assets/js/335.88104646.js"><link rel="prefetch" href="/assets/js/336.b0425564.js"><link rel="prefetch" href="/assets/js/337.6413381a.js"><link rel="prefetch" href="/assets/js/338.468a71ff.js"><link rel="prefetch" href="/assets/js/339.39c8d256.js"><link rel="prefetch" href="/assets/js/34.fec188a0.js"><link rel="prefetch" href="/assets/js/340.6c2f13d9.js"><link rel="prefetch" href="/assets/js/341.d563f7a0.js"><link rel="prefetch" href="/assets/js/342.f644a714.js"><link rel="prefetch" href="/assets/js/343.7577cdc6.js"><link rel="prefetch" href="/assets/js/344.2858b478.js"><link rel="prefetch" href="/assets/js/345.580b30c8.js"><link rel="prefetch" href="/assets/js/346.31937d51.js"><link rel="prefetch" href="/assets/js/347.0cb91c0c.js"><link rel="prefetch" href="/assets/js/348.457d2602.js"><link rel="prefetch" href="/assets/js/349.0f40477a.js"><link rel="prefetch" href="/assets/js/35.a7511c1e.js"><link rel="prefetch" href="/assets/js/350.d135cfba.js"><link rel="prefetch" href="/assets/js/351.e93ead26.js"><link rel="prefetch" href="/assets/js/352.21185cb1.js"><link rel="prefetch" href="/assets/js/354.1bcd3bd7.js"><link rel="prefetch" href="/assets/js/355.5c59a441.js"><link rel="prefetch" href="/assets/js/356.faf1af8d.js"><link rel="prefetch" href="/assets/js/357.75c04705.js"><link rel="prefetch" href="/assets/js/358.ca3a90b8.js"><link rel="prefetch" href="/assets/js/359.855fba63.js"><link rel="prefetch" href="/assets/js/36.4b2d3a4f.js"><link rel="prefetch" href="/assets/js/360.27218a17.js"><link rel="prefetch" href="/assets/js/361.effdafc4.js"><link rel="prefetch" href="/assets/js/362.ded22ed8.js"><link rel="prefetch" href="/assets/js/363.6bfd858a.js"><link rel="prefetch" href="/assets/js/364.33cb94a1.js"><link rel="prefetch" href="/assets/js/365.201d9472.js"><link rel="prefetch" href="/assets/js/366.79ed763f.js"><link rel="prefetch" href="/assets/js/367.134d2beb.js"><link rel="prefetch" href="/assets/js/368.09c105ad.js"><link rel="prefetch" href="/assets/js/369.c292fc98.js"><link rel="prefetch" href="/assets/js/37.c842407e.js"><link rel="prefetch" href="/assets/js/370.c72ef481.js"><link rel="prefetch" href="/assets/js/371.91a9253e.js"><link rel="prefetch" href="/assets/js/372.540333ee.js"><link rel="prefetch" href="/assets/js/373.e1991e99.js"><link rel="prefetch" href="/assets/js/374.643c1cea.js"><link rel="prefetch" href="/assets/js/375.7b57ff77.js"><link rel="prefetch" href="/assets/js/376.3137353e.js"><link rel="prefetch" href="/assets/js/377.1401ad75.js"><link rel="prefetch" href="/assets/js/378.4e2820a1.js"><link rel="prefetch" href="/assets/js/379.72ed9a3c.js"><link rel="prefetch" href="/assets/js/38.6059c476.js"><link rel="prefetch" href="/assets/js/380.5689ddbe.js"><link rel="prefetch" href="/assets/js/381.c0a999f0.js"><link rel="prefetch" href="/assets/js/382.94590ec0.js"><link rel="prefetch" href="/assets/js/383.fb86c446.js"><link rel="prefetch" href="/assets/js/384.36db2c6e.js"><link rel="prefetch" href="/assets/js/385.6d599fe6.js"><link rel="prefetch" href="/assets/js/386.be870130.js"><link rel="prefetch" href="/assets/js/387.bc686a46.js"><link rel="prefetch" href="/assets/js/388.90303374.js"><link rel="prefetch" href="/assets/js/389.6c75c596.js"><link rel="prefetch" href="/assets/js/39.18777c77.js"><link rel="prefetch" href="/assets/js/390.50b8fde5.js"><link rel="prefetch" href="/assets/js/391.4a8a9d82.js"><link rel="prefetch" href="/assets/js/392.4fa2b118.js"><link rel="prefetch" href="/assets/js/393.6fd5e484.js"><link rel="prefetch" href="/assets/js/394.21cd1b25.js"><link rel="prefetch" href="/assets/js/395.d48e07d5.js"><link rel="prefetch" href="/assets/js/396.5f8c78de.js"><link rel="prefetch" href="/assets/js/397.8f1f4f18.js"><link rel="prefetch" href="/assets/js/398.45f67cf6.js"><link rel="prefetch" href="/assets/js/399.58b103d5.js"><link rel="prefetch" href="/assets/js/40.c581224f.js"><link rel="prefetch" href="/assets/js/400.7fca70bc.js"><link rel="prefetch" href="/assets/js/401.457e4e30.js"><link rel="prefetch" href="/assets/js/402.13d27406.js"><link rel="prefetch" href="/assets/js/403.28b9c70f.js"><link rel="prefetch" href="/assets/js/404.982889d5.js"><link rel="prefetch" href="/assets/js/405.997965a4.js"><link rel="prefetch" href="/assets/js/406.9de4bd8f.js"><link rel="prefetch" href="/assets/js/407.22c1b709.js"><link rel="prefetch" href="/assets/js/408.7657b0ab.js"><link rel="prefetch" href="/assets/js/409.1cffd108.js"><link rel="prefetch" href="/assets/js/41.d4842a5b.js"><link rel="prefetch" href="/assets/js/410.b26e1d57.js"><link rel="prefetch" href="/assets/js/411.ddfb8b21.js"><link rel="prefetch" href="/assets/js/412.deeb5e0e.js"><link rel="prefetch" href="/assets/js/413.223b8db3.js"><link rel="prefetch" href="/assets/js/414.03f62538.js"><link rel="prefetch" href="/assets/js/415.aa7d5b53.js"><link rel="prefetch" href="/assets/js/416.cec587b0.js"><link rel="prefetch" href="/assets/js/417.c9a3968a.js"><link rel="prefetch" href="/assets/js/418.78813764.js"><link rel="prefetch" href="/assets/js/419.eb5ade66.js"><link rel="prefetch" href="/assets/js/42.c88c6cb7.js"><link rel="prefetch" href="/assets/js/420.c8463946.js"><link rel="prefetch" href="/assets/js/421.7af022b4.js"><link rel="prefetch" href="/assets/js/422.863655c3.js"><link rel="prefetch" href="/assets/js/423.bfe30a0f.js"><link rel="prefetch" href="/assets/js/424.590b4282.js"><link rel="prefetch" href="/assets/js/425.0c722a85.js"><link rel="prefetch" href="/assets/js/426.49c576ef.js"><link rel="prefetch" href="/assets/js/427.3d3d3823.js"><link rel="prefetch" href="/assets/js/428.4f78ea6c.js"><link rel="prefetch" href="/assets/js/429.5fe617b2.js"><link rel="prefetch" href="/assets/js/43.90ce3a73.js"><link rel="prefetch" href="/assets/js/430.72233f4d.js"><link rel="prefetch" href="/assets/js/431.7a404ba7.js"><link rel="prefetch" href="/assets/js/432.fbbfcb8a.js"><link rel="prefetch" href="/assets/js/433.93b25751.js"><link rel="prefetch" href="/assets/js/434.65d855ed.js"><link rel="prefetch" href="/assets/js/435.14b85953.js"><link rel="prefetch" href="/assets/js/436.c33706ff.js"><link rel="prefetch" href="/assets/js/437.1baa314f.js"><link rel="prefetch" href="/assets/js/438.069136ba.js"><link rel="prefetch" href="/assets/js/439.0b848bcd.js"><link rel="prefetch" href="/assets/js/44.64e262ab.js"><link rel="prefetch" href="/assets/js/440.51fca2af.js"><link rel="prefetch" href="/assets/js/441.8c8f8cc9.js"><link rel="prefetch" href="/assets/js/442.7504dd8e.js"><link rel="prefetch" href="/assets/js/443.3474cd36.js"><link rel="prefetch" href="/assets/js/444.5fb28a3d.js"><link rel="prefetch" href="/assets/js/445.d6af7350.js"><link rel="prefetch" href="/assets/js/446.1ac60bee.js"><link rel="prefetch" href="/assets/js/447.de416e93.js"><link rel="prefetch" href="/assets/js/448.4684720f.js"><link rel="prefetch" href="/assets/js/449.a1bb01c0.js"><link rel="prefetch" href="/assets/js/45.6231efe5.js"><link rel="prefetch" href="/assets/js/450.d175f56a.js"><link rel="prefetch" href="/assets/js/451.5d0f5b0b.js"><link rel="prefetch" href="/assets/js/452.7c97fa86.js"><link rel="prefetch" href="/assets/js/453.e8bf8887.js"><link rel="prefetch" href="/assets/js/454.e6523341.js"><link rel="prefetch" href="/assets/js/455.4a1a0c54.js"><link rel="prefetch" href="/assets/js/456.56f8b1d3.js"><link rel="prefetch" href="/assets/js/457.921cbb60.js"><link rel="prefetch" href="/assets/js/458.1d36727e.js"><link rel="prefetch" href="/assets/js/459.a99c7d50.js"><link rel="prefetch" href="/assets/js/46.9339507a.js"><link rel="prefetch" href="/assets/js/460.eca58a4f.js"><link rel="prefetch" href="/assets/js/461.4e20b7b5.js"><link rel="prefetch" href="/assets/js/462.f967c8ef.js"><link rel="prefetch" href="/assets/js/463.50f98b65.js"><link rel="prefetch" href="/assets/js/464.53a27dd7.js"><link rel="prefetch" href="/assets/js/465.f405390b.js"><link rel="prefetch" href="/assets/js/466.ff9f2146.js"><link rel="prefetch" href="/assets/js/467.721b342d.js"><link rel="prefetch" href="/assets/js/468.65af50d2.js"><link rel="prefetch" href="/assets/js/469.907b109f.js"><link rel="prefetch" href="/assets/js/47.60894af2.js"><link rel="prefetch" href="/assets/js/470.017ad3be.js"><link rel="prefetch" href="/assets/js/471.b514ba1c.js"><link rel="prefetch" href="/assets/js/472.7e20de3c.js"><link rel="prefetch" href="/assets/js/473.d061a8f4.js"><link rel="prefetch" href="/assets/js/474.35f3120e.js"><link rel="prefetch" href="/assets/js/475.b0eaaafa.js"><link rel="prefetch" href="/assets/js/476.0a93303d.js"><link rel="prefetch" href="/assets/js/477.c9ffa963.js"><link rel="prefetch" href="/assets/js/478.c58ad168.js"><link rel="prefetch" href="/assets/js/479.baa2fb5c.js"><link rel="prefetch" href="/assets/js/48.d5735fb1.js"><link rel="prefetch" href="/assets/js/480.db4b72ed.js"><link rel="prefetch" href="/assets/js/481.f9880ad1.js"><link rel="prefetch" href="/assets/js/482.f2e976df.js"><link rel="prefetch" href="/assets/js/483.398fde55.js"><link rel="prefetch" href="/assets/js/484.95f23223.js"><link rel="prefetch" href="/assets/js/485.63ffa136.js"><link rel="prefetch" href="/assets/js/486.db2e0c2b.js"><link rel="prefetch" href="/assets/js/487.ab71eadf.js"><link rel="prefetch" href="/assets/js/488.d24d37c4.js"><link rel="prefetch" href="/assets/js/489.b610403a.js"><link rel="prefetch" href="/assets/js/49.8391c2e1.js"><link rel="prefetch" href="/assets/js/490.a9ca3d3f.js"><link rel="prefetch" href="/assets/js/491.9dae374a.js"><link rel="prefetch" href="/assets/js/492.211497eb.js"><link rel="prefetch" href="/assets/js/493.b89c949c.js"><link rel="prefetch" href="/assets/js/494.38299feb.js"><link rel="prefetch" href="/assets/js/495.049b7f92.js"><link rel="prefetch" href="/assets/js/496.2a2ee823.js"><link rel="prefetch" href="/assets/js/497.03b24330.js"><link rel="prefetch" href="/assets/js/498.3299e21a.js"><link rel="prefetch" href="/assets/js/499.e426da21.js"><link rel="prefetch" href="/assets/js/5.eace4687.js"><link rel="prefetch" href="/assets/js/50.d51914be.js"><link rel="prefetch" href="/assets/js/500.a95dedcb.js"><link rel="prefetch" href="/assets/js/501.fbf7aed5.js"><link rel="prefetch" href="/assets/js/502.236f3361.js"><link rel="prefetch" href="/assets/js/503.74c89220.js"><link rel="prefetch" href="/assets/js/504.e01b0040.js"><link rel="prefetch" href="/assets/js/505.c9fb4bf0.js"><link rel="prefetch" href="/assets/js/506.27b744be.js"><link rel="prefetch" href="/assets/js/507.52ddc0c1.js"><link rel="prefetch" href="/assets/js/508.c1c03934.js"><link rel="prefetch" href="/assets/js/509.549cd70f.js"><link rel="prefetch" href="/assets/js/51.c6284764.js"><link rel="prefetch" href="/assets/js/510.3b69cf75.js"><link rel="prefetch" href="/assets/js/511.f8efe3a9.js"><link rel="prefetch" href="/assets/js/512.5884030d.js"><link rel="prefetch" href="/assets/js/513.d4d58d76.js"><link rel="prefetch" href="/assets/js/514.8d6061b7.js"><link rel="prefetch" href="/assets/js/515.d58e41bc.js"><link rel="prefetch" href="/assets/js/516.407c9790.js"><link rel="prefetch" href="/assets/js/517.ce07dd19.js"><link rel="prefetch" href="/assets/js/518.2842f37d.js"><link rel="prefetch" href="/assets/js/519.f04855de.js"><link rel="prefetch" href="/assets/js/52.0052906b.js"><link rel="prefetch" href="/assets/js/520.33769056.js"><link rel="prefetch" href="/assets/js/521.33e5b0db.js"><link rel="prefetch" href="/assets/js/522.dd724362.js"><link rel="prefetch" href="/assets/js/523.c2b2fe1b.js"><link rel="prefetch" href="/assets/js/524.d503889d.js"><link rel="prefetch" href="/assets/js/525.1791a190.js"><link rel="prefetch" href="/assets/js/526.e97fd226.js"><link rel="prefetch" href="/assets/js/527.d1b3155b.js"><link rel="prefetch" href="/assets/js/528.8b0d61e1.js"><link rel="prefetch" href="/assets/js/529.30a18745.js"><link rel="prefetch" href="/assets/js/53.355eef4b.js"><link rel="prefetch" href="/assets/js/530.3a222133.js"><link rel="prefetch" href="/assets/js/531.f0e1875e.js"><link rel="prefetch" href="/assets/js/532.edaa8a87.js"><link rel="prefetch" href="/assets/js/533.2daeb978.js"><link rel="prefetch" href="/assets/js/534.9dd61465.js"><link rel="prefetch" href="/assets/js/535.03a1f7f3.js"><link rel="prefetch" href="/assets/js/536.c8747dc3.js"><link rel="prefetch" href="/assets/js/537.c07f16f7.js"><link rel="prefetch" href="/assets/js/538.4d7a282b.js"><link rel="prefetch" href="/assets/js/539.e5d8fc44.js"><link rel="prefetch" href="/assets/js/54.ca948b5b.js"><link rel="prefetch" href="/assets/js/540.568b7bb9.js"><link rel="prefetch" href="/assets/js/541.cc3c7bf3.js"><link rel="prefetch" href="/assets/js/542.1e7d71fb.js"><link rel="prefetch" href="/assets/js/543.ce0b8bc5.js"><link rel="prefetch" href="/assets/js/544.6984f071.js"><link rel="prefetch" href="/assets/js/545.85fcefdc.js"><link rel="prefetch" href="/assets/js/546.054bdeeb.js"><link rel="prefetch" href="/assets/js/547.7d6e42f8.js"><link rel="prefetch" href="/assets/js/548.9fdd0357.js"><link rel="prefetch" href="/assets/js/549.e3c4bda8.js"><link rel="prefetch" href="/assets/js/55.9907a531.js"><link rel="prefetch" href="/assets/js/550.2723036d.js"><link rel="prefetch" href="/assets/js/551.603480e2.js"><link rel="prefetch" href="/assets/js/552.cfbb9201.js"><link rel="prefetch" href="/assets/js/553.4f157b97.js"><link rel="prefetch" href="/assets/js/554.be5b47c5.js"><link rel="prefetch" href="/assets/js/555.ced4f3d3.js"><link rel="prefetch" href="/assets/js/556.e87c33c8.js"><link rel="prefetch" href="/assets/js/557.cbb48495.js"><link rel="prefetch" href="/assets/js/558.f7482f86.js"><link rel="prefetch" href="/assets/js/559.e84a64ab.js"><link rel="prefetch" href="/assets/js/56.90d1bc94.js"><link rel="prefetch" href="/assets/js/560.5cecae0c.js"><link rel="prefetch" href="/assets/js/561.db8f05dd.js"><link rel="prefetch" href="/assets/js/562.c605ffae.js"><link rel="prefetch" href="/assets/js/563.7cb7ad86.js"><link rel="prefetch" href="/assets/js/564.4644c5a6.js"><link rel="prefetch" href="/assets/js/565.32642e9c.js"><link rel="prefetch" href="/assets/js/566.9a4311be.js"><link rel="prefetch" href="/assets/js/567.d0683527.js"><link rel="prefetch" href="/assets/js/568.81128faf.js"><link rel="prefetch" href="/assets/js/569.ce6d29a6.js"><link rel="prefetch" href="/assets/js/57.c86cddb9.js"><link rel="prefetch" href="/assets/js/570.2456b712.js"><link rel="prefetch" href="/assets/js/571.aac9ba80.js"><link rel="prefetch" href="/assets/js/572.5f9a6d45.js"><link rel="prefetch" href="/assets/js/573.2a7779ad.js"><link rel="prefetch" href="/assets/js/574.0742d701.js"><link rel="prefetch" href="/assets/js/575.b5ae9dd1.js"><link rel="prefetch" href="/assets/js/576.abe5b760.js"><link rel="prefetch" href="/assets/js/577.2e0cba12.js"><link rel="prefetch" href="/assets/js/578.98af2add.js"><link rel="prefetch" href="/assets/js/579.9aed8c04.js"><link rel="prefetch" href="/assets/js/58.19b45ba6.js"><link rel="prefetch" href="/assets/js/580.1595ea15.js"><link rel="prefetch" href="/assets/js/581.fcf612e4.js"><link rel="prefetch" href="/assets/js/582.910c54de.js"><link rel="prefetch" href="/assets/js/583.a34483d9.js"><link rel="prefetch" href="/assets/js/584.70d64527.js"><link rel="prefetch" href="/assets/js/585.5ea6b3e5.js"><link rel="prefetch" href="/assets/js/586.db13f96e.js"><link rel="prefetch" href="/assets/js/587.bf883385.js"><link rel="prefetch" href="/assets/js/588.c1466d25.js"><link rel="prefetch" href="/assets/js/589.4ec92587.js"><link rel="prefetch" href="/assets/js/59.299b0b27.js"><link rel="prefetch" href="/assets/js/590.7c155fdb.js"><link rel="prefetch" href="/assets/js/591.ebae3557.js"><link rel="prefetch" href="/assets/js/592.0956ab15.js"><link rel="prefetch" href="/assets/js/593.ea31c530.js"><link rel="prefetch" href="/assets/js/594.658fca38.js"><link rel="prefetch" href="/assets/js/595.ddbbdc10.js"><link rel="prefetch" href="/assets/js/596.c24c8026.js"><link rel="prefetch" href="/assets/js/597.88748ffe.js"><link rel="prefetch" href="/assets/js/598.cec78e4d.js"><link rel="prefetch" href="/assets/js/599.a8f7a498.js"><link rel="prefetch" href="/assets/js/6.008dd0d6.js"><link rel="prefetch" href="/assets/js/60.287cfb0d.js"><link rel="prefetch" href="/assets/js/600.979d8dda.js"><link rel="prefetch" href="/assets/js/601.445e0ae7.js"><link rel="prefetch" href="/assets/js/602.d4b357d6.js"><link rel="prefetch" href="/assets/js/603.f5555cc4.js"><link rel="prefetch" href="/assets/js/604.b97d0641.js"><link rel="prefetch" href="/assets/js/605.b1adcf8f.js"><link rel="prefetch" href="/assets/js/606.099c5cc0.js"><link rel="prefetch" href="/assets/js/607.0ccc3723.js"><link rel="prefetch" href="/assets/js/608.ceda733e.js"><link rel="prefetch" href="/assets/js/609.d644e9f4.js"><link rel="prefetch" href="/assets/js/61.101494e3.js"><link rel="prefetch" href="/assets/js/610.97edc5b7.js"><link rel="prefetch" href="/assets/js/611.6a63d033.js"><link rel="prefetch" href="/assets/js/612.77cf2e09.js"><link rel="prefetch" href="/assets/js/613.454523c0.js"><link rel="prefetch" href="/assets/js/614.586f59e3.js"><link rel="prefetch" href="/assets/js/615.512e958b.js"><link rel="prefetch" href="/assets/js/616.0a455969.js"><link rel="prefetch" href="/assets/js/617.7657723d.js"><link rel="prefetch" href="/assets/js/618.e1e77dbc.js"><link rel="prefetch" href="/assets/js/619.8b9ac557.js"><link rel="prefetch" href="/assets/js/62.3de0bc0b.js"><link rel="prefetch" href="/assets/js/620.c7d354b1.js"><link rel="prefetch" href="/assets/js/621.94f87c1f.js"><link rel="prefetch" href="/assets/js/622.7ae48b4b.js"><link rel="prefetch" href="/assets/js/623.3c371fca.js"><link rel="prefetch" href="/assets/js/624.dad907c8.js"><link rel="prefetch" href="/assets/js/625.a31335e9.js"><link rel="prefetch" href="/assets/js/626.428bab7e.js"><link rel="prefetch" href="/assets/js/627.5823614e.js"><link rel="prefetch" href="/assets/js/628.c8ae8496.js"><link rel="prefetch" href="/assets/js/629.6e383535.js"><link rel="prefetch" href="/assets/js/63.26b80690.js"><link rel="prefetch" href="/assets/js/630.444ca9ee.js"><link rel="prefetch" href="/assets/js/631.b311c084.js"><link rel="prefetch" href="/assets/js/632.74224a1c.js"><link rel="prefetch" href="/assets/js/633.e7884efd.js"><link rel="prefetch" href="/assets/js/634.e46a2f9c.js"><link rel="prefetch" href="/assets/js/635.ec46017b.js"><link rel="prefetch" href="/assets/js/636.16f35f64.js"><link rel="prefetch" href="/assets/js/637.47e17cac.js"><link rel="prefetch" href="/assets/js/638.f551e4bc.js"><link rel="prefetch" href="/assets/js/639.0a2acabd.js"><link rel="prefetch" href="/assets/js/64.f0ead63e.js"><link rel="prefetch" href="/assets/js/640.311cc5d7.js"><link rel="prefetch" href="/assets/js/641.ce05a761.js"><link rel="prefetch" href="/assets/js/642.7aaa4ac9.js"><link rel="prefetch" href="/assets/js/643.aac8e411.js"><link rel="prefetch" href="/assets/js/644.14b46f57.js"><link rel="prefetch" href="/assets/js/645.a0106e32.js"><link rel="prefetch" href="/assets/js/646.3880e83e.js"><link rel="prefetch" href="/assets/js/647.c48d4743.js"><link rel="prefetch" href="/assets/js/648.0ed73224.js"><link rel="prefetch" href="/assets/js/649.4c4e2394.js"><link rel="prefetch" href="/assets/js/65.af2d3fb6.js"><link rel="prefetch" href="/assets/js/66.6b8a0a43.js"><link rel="prefetch" href="/assets/js/67.61ea30bb.js"><link rel="prefetch" href="/assets/js/68.a38a14f8.js"><link rel="prefetch" href="/assets/js/69.7bf89bfe.js"><link rel="prefetch" href="/assets/js/7.080f75db.js"><link rel="prefetch" href="/assets/js/70.8cc7beca.js"><link rel="prefetch" href="/assets/js/71.b40ada4d.js"><link rel="prefetch" href="/assets/js/72.e2d60055.js"><link rel="prefetch" href="/assets/js/73.399ce982.js"><link rel="prefetch" href="/assets/js/74.f1282d94.js"><link rel="prefetch" href="/assets/js/75.1bb0e055.js"><link rel="prefetch" href="/assets/js/76.5985f97a.js"><link rel="prefetch" href="/assets/js/77.e6ce049c.js"><link rel="prefetch" href="/assets/js/78.46da2fca.js"><link rel="prefetch" href="/assets/js/79.3394bd3a.js"><link rel="prefetch" href="/assets/js/8.d214e90e.js"><link rel="prefetch" href="/assets/js/80.544a992f.js"><link rel="prefetch" href="/assets/js/81.4502b168.js"><link rel="prefetch" href="/assets/js/82.99c8888e.js"><link rel="prefetch" href="/assets/js/83.d2451960.js"><link rel="prefetch" href="/assets/js/84.45605d38.js"><link rel="prefetch" href="/assets/js/85.20d4a699.js"><link rel="prefetch" href="/assets/js/86.a001dd4e.js"><link rel="prefetch" href="/assets/js/87.f97143e5.js"><link rel="prefetch" href="/assets/js/88.74fc80d1.js"><link rel="prefetch" href="/assets/js/89.de6dd42f.js"><link rel="prefetch" href="/assets/js/9.15e59c54.js"><link rel="prefetch" href="/assets/js/90.449bdd39.js"><link rel="prefetch" href="/assets/js/91.e0f253e2.js"><link rel="prefetch" href="/assets/js/92.a91c44ff.js"><link rel="prefetch" href="/assets/js/93.0619a7be.js"><link rel="prefetch" href="/assets/js/94.c068c916.js"><link rel="prefetch" href="/assets/js/95.5d813553.js"><link rel="prefetch" href="/assets/js/96.1174373e.js"><link rel="prefetch" href="/assets/js/97.19f7e28d.js"><link rel="prefetch" href="/assets/js/98.cb6fd2d8.js"><link rel="prefetch" href="/assets/js/99.e9b31298.js"><link rel="prefetch" href="/assets/js/vendors~docsearch.1288603f.js">
    <link rel="stylesheet" href="/assets/css/0.styles.c79f5191.css">
  </head>
  <body>
    <div id="app" data-server-rendered="true"><div class="theme-container"><header class="navbar"><div class="sidebar-button"><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" role="img" viewBox="0 0 448 512" class="icon"><path fill="currentColor" d="M436 124H12c-6.627 0-12-5.373-12-12V80c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12z"></path></svg></div> <a href="/zh/" class="home-link router-link-active"><img src="/img/logo.png" alt=" " class="logo"></a> <div class="links"><div class="search-box"><input aria-label="Search" autocomplete="off" spellcheck="false" value=""> <!----></div> <nav class="nav-links can-hide"><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">文档</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/zh/UserGuide/Master/QuickStart/QuickStart.html" class="nav-link">In progress</a></li><li class="dropdown-item"><!----> <a href="/zh/UserGuide/V0.12.x/QuickStart/QuickStart.html" class="nav-link">V0.12.x</a></li><li class="dropdown-item"><!----> <a href="/zh/UserGuide/V0.11.x/Get Started/QuickStart.html" class="nav-link">V0.11.x</a></li><li class="dropdown-item"><!----> <a href="/zh/UserGuide/V0.10.x/Get Started/QuickStart.html" class="nav-link">V0.10.x</a></li><li class="dropdown-item"><!----> <a href="/zh/UserGuide/V0.9.x/0-Get Started/1-QuickStart.html" class="nav-link">V0.9.x</a></li><li class="dropdown-item"><!----> <a href="/zh/UserGuide/V0.8.x/0-Get Started/1-QuickStart.html" class="nav-link">V0.8.x</a></li></ul></div></div><div class="nav-item"><a href="/zh/SystemDesign/Architecture/Architecture.html" class="nav-link">系统设计</a></div><div class="nav-item"><a href="/zh/Download/" class="nav-link">下载</a></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">社区</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="https://cwiki.apache.org/confluence/display/iotdb" class="nav-link external">
  Wiki
  <!----></a></li><li class="dropdown-item"><!----> <a href="/zh/Community/Community-Project Committers.html" class="nav-link">开发人员</a></li><li class="dropdown-item"><!----> <a href="/zh/Community/Community-Powered By.html" class="nav-link">技术支持</a></li><li class="dropdown-item"><!----> <a href="/Community/Materials.html" class="nav-link">活动与报告</a></li><li class="dropdown-item"><!----> <a href="/zh/Community/Feedback.html" class="nav-link">交流与反馈</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">开发</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/zh/Development/VoteRelease.html" class="nav-link">如何投票</a></li><li class="dropdown-item"><!----> <a href="/zh/Development/HowToCommit.html" class="nav-link">如何提交代码</a></li><li class="dropdown-item"><!----> <a href="/zh/Development/Committer.html" class="nav-link">成为Committer</a></li><li class="dropdown-item"><!----> <a href="/zh/Development/ContributeGuide.html" class="nav-link">项目开发指南</a></li><li class="dropdown-item"><!----> <a href="/zh/Development/format-changelist.html" class="nav-link">TsFile的更改列表</a></li><li class="dropdown-item"><!----> <a href="/zh/Development/rpc-changelist.html" class="nav-link">RPC变更清单</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">ASF</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="http://www.apache.org/" class="nav-link external">
  基金会
  <!----></a></li><li class="dropdown-item"><!----> <a href="http://www.apache.org/licenses/" class="nav-link external">
  许可证
  <!----></a></li><li class="dropdown-item"><!----> <a href="http://www.apache.org/security/" class="nav-link external">
  安全
  <!----></a></li><li class="dropdown-item"><!----> <a href="http://www.apache.org/foundation/sponsorship.html" class="nav-link external">
  赞助
  <!----></a></li><li class="dropdown-item"><!----> <a href="http://www.apache.org/foundation/thanks.html" class="nav-link external">
  致谢
  <!----></a></li><li class="dropdown-item"><!----> <a href="http://www.apache.org/events/current-event" class="nav-link external">
  活动
  <!----></a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">语言</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/SystemDesign/DataQuery/GroupByQuery.html" class="nav-link">English</a></li><li class="dropdown-item"><!----> <a href="/zh/SystemDesign/DataQuery/GroupByQuery.html" aria-current="page" class="nav-link router-link-exact-active router-link-active">简体中文</a></li></ul></div></div> <a href="https://github.com/apache/iotdb.git" target="_blank" rel="noopener noreferrer" class="repo-link">
    gitHub
    <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav></div></header> <div class="sidebar-mask"></div> <aside class="sidebar"><nav class="nav-links"><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">文档</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/zh/UserGuide/Master/QuickStart/QuickStart.html" class="nav-link">In progress</a></li><li class="dropdown-item"><!----> <a href="/zh/UserGuide/V0.12.x/QuickStart/QuickStart.html" class="nav-link">V0.12.x</a></li><li class="dropdown-item"><!----> <a href="/zh/UserGuide/V0.11.x/Get Started/QuickStart.html" class="nav-link">V0.11.x</a></li><li class="dropdown-item"><!----> <a href="/zh/UserGuide/V0.10.x/Get Started/QuickStart.html" class="nav-link">V0.10.x</a></li><li class="dropdown-item"><!----> <a href="/zh/UserGuide/V0.9.x/0-Get Started/1-QuickStart.html" class="nav-link">V0.9.x</a></li><li class="dropdown-item"><!----> <a href="/zh/UserGuide/V0.8.x/0-Get Started/1-QuickStart.html" class="nav-link">V0.8.x</a></li></ul></div></div><div class="nav-item"><a href="/zh/SystemDesign/Architecture/Architecture.html" class="nav-link">系统设计</a></div><div class="nav-item"><a href="/zh/Download/" class="nav-link">下载</a></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">社区</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="https://cwiki.apache.org/confluence/display/iotdb" class="nav-link external">
  Wiki
  <!----></a></li><li class="dropdown-item"><!----> <a href="/zh/Community/Community-Project Committers.html" class="nav-link">开发人员</a></li><li class="dropdown-item"><!----> <a href="/zh/Community/Community-Powered By.html" class="nav-link">技术支持</a></li><li class="dropdown-item"><!----> <a href="/Community/Materials.html" class="nav-link">活动与报告</a></li><li class="dropdown-item"><!----> <a href="/zh/Community/Feedback.html" class="nav-link">交流与反馈</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">开发</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/zh/Development/VoteRelease.html" class="nav-link">如何投票</a></li><li class="dropdown-item"><!----> <a href="/zh/Development/HowToCommit.html" class="nav-link">如何提交代码</a></li><li class="dropdown-item"><!----> <a href="/zh/Development/Committer.html" class="nav-link">成为Committer</a></li><li class="dropdown-item"><!----> <a href="/zh/Development/ContributeGuide.html" class="nav-link">项目开发指南</a></li><li class="dropdown-item"><!----> <a href="/zh/Development/format-changelist.html" class="nav-link">TsFile的更改列表</a></li><li class="dropdown-item"><!----> <a href="/zh/Development/rpc-changelist.html" class="nav-link">RPC变更清单</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">ASF</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="http://www.apache.org/" class="nav-link external">
  基金会
  <!----></a></li><li class="dropdown-item"><!----> <a href="http://www.apache.org/licenses/" class="nav-link external">
  许可证
  <!----></a></li><li class="dropdown-item"><!----> <a href="http://www.apache.org/security/" class="nav-link external">
  安全
  <!----></a></li><li class="dropdown-item"><!----> <a href="http://www.apache.org/foundation/sponsorship.html" class="nav-link external">
  赞助
  <!----></a></li><li class="dropdown-item"><!----> <a href="http://www.apache.org/foundation/thanks.html" class="nav-link external">
  致谢
  <!----></a></li><li class="dropdown-item"><!----> <a href="http://www.apache.org/events/current-event" class="nav-link external">
  活动
  <!----></a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">语言</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/SystemDesign/DataQuery/GroupByQuery.html" class="nav-link">English</a></li><li class="dropdown-item"><!----> <a href="/zh/SystemDesign/DataQuery/GroupByQuery.html" aria-current="page" class="nav-link router-link-exact-active router-link-active">简体中文</a></li></ul></div></div> <a href="https://github.com/apache/iotdb.git" target="_blank" rel="noopener noreferrer" class="repo-link">
    gitHub
    <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav>  <ul class="sidebar-links"><li><section class="sidebar-group depth-0"><p class="sidebar-heading"><span>系统设计</span> <!----></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>应用概览</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>TsFile</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>查询引擎</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>元数据管理</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>存储引擎</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading open"><span>数据查询</span> <span class="arrow down"></span></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/zh/SystemDesign/DataQuery/DataQuery.html" class="sidebar-link">数据查询</a></li><li><a href="/zh/SystemDesign/DataQuery/QueryFundamentals.html" class="sidebar-link">查询基础介绍</a></li><li><a href="/zh/SystemDesign/DataQuery/SeriesReader.html" class="sidebar-link">查询基础组件</a></li><li><a href="/zh/SystemDesign/DataQuery/RawDataQuery.html" class="sidebar-link">原始数据查询</a></li><li><a href="/zh/SystemDesign/DataQuery/AggregationQuery.html" class="sidebar-link">聚合查询</a></li><li><a href="/zh/SystemDesign/DataQuery/GroupByQuery.html" aria-current="page" class="active sidebar-link">降采样查询</a></li><li><a href="/zh/SystemDesign/DataQuery/LastQuery.html" class="sidebar-link">最近时间戳 Last 查询</a></li><li><a href="/zh/SystemDesign/DataQuery/AlignByDeviceQuery.html" class="sidebar-link">按设备对齐查询</a></li><li><a href="/zh/SystemDesign/DataQuery/FillFunction.html" class="sidebar-link">空值填充</a></li><li><a href="/zh/SystemDesign/DataQuery/GroupByFillQuery.html" class="sidebar-link">降采样补空值查询</a></li><li><a href="/zh/SystemDesign/DataQuery/OrderByTimeQuery.html" class="sidebar-link">按时间倒序查询</a></li></ul></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>工具</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>连接器</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>客户端</span> <span class="arrow right"></span></p> <!----></section></li></ul> </aside> <main class="page"> <div class="content content__default"><h1 id="降采样查询"><a href="#降采样查询" class="header-anchor">#</a> 降采样查询</h1> <ul><li>org.apache.iotdb.db.query.dataset.groupby.GroupByEngineDataSet</li></ul> <p>降采样查询的结果集都会继承 <code>GroupByEngineDataSet</code>，该类包含如下字段：</p> <ul><li>protected long queryId</li> <li>private long interval</li> <li>private long slidingStep</li></ul> <p>以下两个字段针对整个查询，时间段为左闭右开，即 <code>[startTime, endTime)</code>：</p> <ul><li>private long startTime</li> <li>private long endTime</li></ul> <p>以下字段针对当前分段，时间段为左闭右开，即 <code>[curStartTime, curEndTime)</code></p> <ul><li>protected long curStartTime;</li> <li>protected long curEndTime;</li> <li>private int usedIndex;</li> <li>protected boolean hasCachedTimeInterval;</li></ul> <p><code>GroupByEngineDataSet</code> 的核心方法很容易，首先根据是否有缓存的时间段判断是否有下一分段，有则返回 <code>true</code>；如果没有就计算分段开始时间，将 <code>usedIndex</code> 增加1。如果分段开始时间已经超过了查询结束时间，返回 <code>false</code>，否则计算查询结束时间，将 <code>hasCachedTimeInterval</code> 置为<code>true</code>，并返回 <code>true</code>：</p> <div class="language- line-numbers-mode"><pre class="language-text"><code>protected boolean hasNextWithoutConstraint() {
  if (hasCachedTimeInterval) {
    return true;
  }

  curStartTime = usedIndex * slidingStep + startTime;
  usedIndex++;
  if (curStartTime &lt; endTime) {
    hasCachedTimeInterval = true;
    curEndTime = Math.min(curStartTime + interval, endTime);
    return true;
  } else {
    return false;
  }
}
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br></div></div><h2 id="不带值过滤条件的降采样查询"><a href="#不带值过滤条件的降采样查询" class="header-anchor">#</a> 不带值过滤条件的降采样查询</h2> <p>不带值过滤条件的降采样查询逻辑主要在 <code>GroupByWithoutValueFilterDataSet</code> 类中，该类继承了 <code>GroupByEngineDataSet</code>。</p> <p>该类有如下关键字段：</p> <ul><li><p>private Map&lt;Path, GroupByExecutor&gt; pathExecutors 针对于相同 <code>Path</code> 的聚合函数进行归类，并封装成 <code>GroupByExecutor</code> ,
<code>GroupByExecutor</code> 封装了每个 <code>Path</code> 的数据计算逻辑和方法，在后面介绍</p></li> <li><p>private TimeRange timeRange 将每次计算的时间区间封装成对象，用于判断 <code>Statistics</code> 是否可以直接参与计算</p></li> <li><p>private Filter timeFilter   将用户定义的查询区间生成为 <code>Filter</code> 对象，用来过滤可用的<code>文件</code>、<code>chunk</code>、<code>page</code></p></li></ul> <p>首先，在初始化 <code>initGroupBy()</code> 方法中，根据表达式计算出 <code>timeFilter</code>，并为每个 <code>path</code> 生成 <code>GroupByExecutor</code> 。</p> <p><code>nextWithoutConstraint()</code> 方法通过调用 <code>GroupByExecutor.calcResult()</code> 方法计算出每个 <code>Path</code> 内的所有聚合方法的聚合值 <code>aggregateResults</code>。
以下方法用于将结果列表转化为 RowRecord，需要注意列表中没有结果时， RowRecord 中添加 <code>null</code>：</p> <div class="language- line-numbers-mode"><pre class="language-text"><code>for (AggregateResult res : fields) {
  if (res == null) {
    record.addField(null);
    continue;
  }
  record.addField(res.getResult(), res.getResultDataType());
}
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><h3 id="groupbyexecutor"><a href="#groupbyexecutor" class="header-anchor">#</a> GroupByExecutor</h3> <p>封装了相同 path 下的所有聚合函数的计算方法，该类有如下关键字段：</p> <ul><li>private IAggregateReader reader 读取当前 <code>Path</code> 数据用到的 <code>SeriesAggregateReader</code></li> <li>private BatchData preCachedData 每次从 <code>Reader</code> 读取的数据是一批，很有可能会超过当前的时间段，那么这个 <code>BatchData</code> 就会被缓存留给下一次使用</li> <li>private List&lt;Pair&lt;AggregateResult, Integer&gt;&gt; results 存储了当前 <code>Path</code> 里所有的聚合方法，
例如：<code>select count(a),sum(a),avg(b)</code> ，<code>count</code> 和 <code>sum</code> 方法就被存到一起。
右侧的 <code>Integer</code> 用于结果集转化为RowRecord之前，需要将其顺序还原为用户查询的顺序。</li></ul> <h4 id="主要方法"><a href="#主要方法" class="header-anchor">#</a> 主要方法</h4> <div class="language- line-numbers-mode"><pre class="language-text"><code>//从 reader 中读取数据，并计算，该类的主方法。
private List&lt;Pair&lt;AggregateResult, Integer&gt;&gt; calcResult() throws IOException, QueryProcessException;

//添加当前 path 的聚合操作
private void addAggregateResult(AggregateResult aggrResult, int index);

//判断当前 path 是否已经完成了所有的聚合计算
private boolean isEndCalc();

//从上次计算没有使用完缓存的 BatchData 中计算结果
private boolean calcFromCacheData() throws IOException;

//使用 BatchData 计算
private void calcFromBatch(BatchData batchData) throws IOException;

//使用 Page 或 Chunk 的 Statistics 信息直接计算结果
private void calcFromStatistics(Statistics statistics) throws QueryProcessException;

//清空所有计算结果
private void resetAggregateResults();

//遍历并计算 page 中的数据
private boolean readAndCalcFromPage() throws IOException, QueryProcessException;

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br></div></div><p><code>GroupByExecutor</code> 中因为相同 <code>path</code> 的不同聚合函数使用的数据是相同的，所以在入口方法 <code>calcResult</code> 中负责读取该 <code>Path</code> 的所有数据,
取出来的数据再调用 <code>calcFromBatch</code> 方法完成遍历所有聚合函数对 <code>BatchData</code> 的计算。</p> <p><code>calcResult</code> 方法返回当前 Path 下的所有AggregateResult，以及当前聚合值在用户查询顺序里的位置，其主要逻辑：</p> <div class="language- line-numbers-mode"><pre class="language-text"><code>//把上次遗留的数据先做计算，如果能直接获得结果就结束计算
if (calcFromCacheData()) {
    return results;
}

//因为一个chunk是包含多个page的，那么必须先使用完当前chunk的page，再打开下一个chunk
if (readAndCalcFromPage()) {
    return results;
}

//遗留的数据如果计算完了就要打开新的chunk继续计算
while (reader.hasNextChunk()) {
    Statistics chunkStatistics = reader.currentChunkStatistics();
      // 判断能否使用 Statistics，并执行计算
       ....
      // 跳过当前chunk
      reader.skipCurrentChunk();
      // 如果已经获取到了所有结果就结束计算
      if (isEndCalc()) {
        return true;
      }
      continue;
    }
    //如果不能使用 chunkStatistics 就需要使用page数据计算
    if (readAndCalcFromPage()) {
      return results;
    }
}
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br></div></div><p><code>readAndCalcFromPage</code> 方法是从当前打开的chunk中获取page的数据，并计算聚合结果。当完成所有计算时返回 true，否则返回 false。主要逻辑：</p> <div class="language- line-numbers-mode"><pre class="language-text"><code>while (reader.hasNextPage()) {
    Statistics pageStatistics = reader.currentPageStatistics();
    //只有page与其它page不相交时，才能使用 pageStatistics
    if (pageStatistics != null) {
        // 判断能否使用 Statistics，并执行计算
        ....
        // 跳过当前page
        reader.skipCurrentPage();
        // 如果已经获取到了所有结果就结束计算
        if (isEndCalc()) {
          return true;
        }
        continue;
      }
    }
    // 不能使用 Statistics 时，只能取出所有数据进行计算
    BatchData batchData = reader.nextPage();
    if (batchData == null || !batchData.hasCurrent()) {
      continue;
    }
    // 如果刚打开的page就超过时间范围，缓存取出来的数据并直接结束计算
    if (batchData.currentTime() &gt;= curEndTime) {
      preCachedData = batchData;
      return true;
    }
    //执行计算
    calcFromBatch(batchData);
    ...
}

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br><span class="line-number">30</span><br></div></div><p><code>calcFromBatch</code> 方法是对于取出的BatchData数据，遍历所有聚合函数进行计算，主要逻辑为：</p> <div class="language- line-numbers-mode"><pre class="language-text"><code>for (Pair&lt;AggregateResult, Integer&gt; result : results) {
    //如果某个函数已经完成了计算，就不在进行计算了，比如最小值这种计算
    if (result.left.isCalculatedAggregationResult()) {
      continue;
    }
    // 执行计算
    ....
}
//判断当前的 batchdata 里的数据是否还能被下次使用，如果能则加到缓存中
if (batchData.getMaxTimestamp() &gt;= curEndTime) {
    preCachedData = batchData;
}
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br></div></div><h2 id="带值过滤条件的聚合查询"><a href="#带值过滤条件的聚合查询" class="header-anchor">#</a> 带值过滤条件的聚合查询</h2> <p>带值过滤条件的降采样查询逻辑主要在 <code>GroupByWithValueFilterDataSet</code> 类中，该类继承了 <code>GroupByEngineDataSet</code>。</p> <p>该类有如下关键字段：</p> <ul><li><div class="language- line-numbers-mode"><pre class="language-text"><code>private List&lt;IReaderByTimestamp&gt; allDataReaderList
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div></li> <li><p>private GroupByPlan groupByTimePlan</p></li> <li><p>private TimeGenerator timestampGenerator</p></li> <li><p>private long timestamp 用于为下一个 group by 分区缓存 timestamp</p></li> <li><p>private boolean hasCachedTimestamp 用于判断是否有为下一个 group by 分区缓存 timestamp</p></li> <li><p>private int timeStampFetchSize 是 group by 计算 batch 的大小</p></li></ul> <p>首先，在初始化 <code>initGroupBy()</code> 方法中，根据表达式创建 <code>timestampGenerator</code>；然后为每一个时间序列创建一个 <code>SeriesReaderByTimestamp</code>，放到 <code>allDataReaderList</code>列表中</p> <p>初始化完成后，调用 <code>nextWithoutConstraint()</code> 方法更新结果。如果有为下一个 group by 分区缓存 timestamp，且时间符合要求，则将其加入 <code>timestampArray</code> 中，否则直接返回 <code>aggregateResultList</code> 结果；在没有为下一个 group by 分区缓存 timestamp 的情况下，使用 <code>timestampGenerator</code> 进行遍历：</p> <div class="language- line-numbers-mode"><pre class="language-text"><code>while (timestampGenerator.hasNext()) {
  // 调用 constructTimeArrayForOneCal() 方法，得到 timestamp 列表
  timeArrayLength = constructTimeArrayForOneCal(timestampArray, timeArrayLength);

  // 调用 updateResultUsingTimestamps() 方法，使用 timestamp 列表计算聚合结果
  for (int i = 0; i &lt; paths.size(); i++) {
    aggregateResultList.get(i).updateResultUsingTimestamps(
        timestampArray, timeArrayLength, allDataReaderList.get(i));
  }

  timeArrayLength = 0;
  // 判断是否到结束
  if (timestamp &gt;= curEndTime) {
    hasCachedTimestamp = true;
    break;
  }
}
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br></div></div><p>其中的 <code>constructTimeArrayForOneCal()</code> 方法遍历 timestampGenerator 构建 timestamp 列表：</p> <div class="language- line-numbers-mode"><pre class="language-text"><code>for (int cnt = 1; cnt &lt; timeStampFetchSize &amp;&amp; timestampGenerator.hasNext(); cnt++) {
  timestamp = timestampGenerator.next();
  if (timestamp &lt; curEndTime) {
    timestampArray[timeArrayLength++] = timestamp;
  } else {
    hasCachedTimestamp = true;
    break;
  }
}
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><h2 id="使用level来汇总降采样的总点数"><a href="#使用level来汇总降采样的总点数" class="header-anchor">#</a> 使用Level来汇总降采样的总点数</h2> <p>降采样后，我们也可以使用level关键字来进一步汇总点数。</p> <p>这个逻辑在 <code>GroupByTimeDataSet</code>类里。</p> <ol><li><p>首先，把所有涉及到的时序按level来进行汇集，最后的路径。</p> <blockquote><p>例如把root.sg1.d1.s0,root.sg1.d2.s1按level=1汇集成root.sg1。</p></blockquote></li> <li><p>然后调用上述的降采样逻辑求出所有时序的总点数信息，这个会返回RowRecord数据结构。</p></li> <li><p>最后，把降采样返回的RowRecord按上述的final paths，进行累加，组合成新的RowRecord。</p> <blockquote><p>例如，把《root.sg1.d1.s0,3》，《root.sg1.d2.s1，4》聚合成《root.sg1，7》</p></blockquote></li></ol> <blockquote><p>注意:</p> <ol><li>这里只支持count操作</li> <li>root的层级level=0</li></ol></blockquote></div> <div class="page-nav"><p class="inner"><span class="prev">
        ←
        <a href="/zh/SystemDesign/DataQuery/AggregationQuery.html" class="prev">
          聚合查询
        </a></span> <span class="next"><a href="/zh/SystemDesign/DataQuery/LastQuery.html">
          最近时间戳 Last 查询
        </a>
        →
      </span></p></div> <p style="text-align: center;">Copyright © 2021 The Apache Software Foundation.<br>
     Apache and the Apache feather logo are trademarks of The Apache Software Foundation</p> <p style="text-align: center; margin-top: 10px; color: #444">
    Contact us: Join QQ Group 659990460 | Add friend <i>tietouqiao</i> and be invited to Wechat Group<br>
    see <a href="https://github.com/apache/iotdb/issues/1995">Join the community</a> for more</p></main></div><div class="global-ui"></div></div>
    <script src="/assets/js/app.35ba4ac3.js" defer></script><script src="/assets/js/3.96a076a8.js" defer></script><script src="/assets/js/4.a65360c5.js" defer></script><script src="/assets/js/353.d21f105a.js" defer></script>
  </body>
</html>