ClickHouse之初步认识

最近在Percona的blog上看到一篇文章：Column Store Database Benchmarks: MariaDB ColumnStore vs. Clickhouse vs. Apache Spark，从中可以看到Clickhouse的性能完爆MariaDB ColumnStore和 Spark。于是对Clickhouse产生了浓厚的兴趣，所以也打算进行学习。目前Clickhouse还没有中文文档，学习起来还是有点费劲。Percona的另一篇博客介绍Clickhouse的也可以看看。ClickHouse: New Open Source Columnar Database，其中这里也有一篇文章也可以看看：彪悍开源的分析数据库-ClickHouse

那么ClickHouse到底是啥？

1. 开源的列存储数据库管理系统

2. 支持线性扩展

3. 简单方便

4. 高可靠性

5. 容错（支持多主机异步复制，可以跨多个数据中心部署。 单个节点或整个数据中心的停机时间不会影响系统的读写可用性）

ClickHouse关键功能和应用场景:

更加详细的可以参考官方文档。

目前ClickHouse对ubuntu系统支持比较友好，对于centos就差一点。Ubuntu有deb包可以直接安装。对于centos的则需要自己编译。本人在折腾很久都没有编译出来，最后放弃了。无意中看到了google邮件组中有人提到RPM包，有人搞了yum源，可以直接安装，这才解放。对于想自己编译的同学，可以参考：https://github.com/yandex/ClickHouse/blob/master/doc/build.md，下面进行yum安装

1. 添加yum源

yum-config-manager --add-repo http://repo.red-soft.biz/repos/clickhouse/repo/clickhouse-el6.repo

2.  安装：

yum install clickhouse-server clickhouse-client clickhouse-server-common clickhouse-compressor

3. 添加用户clickhouse

useradd clickhouse

4. 启动clickhouse

/etc/init.d/clickhouse-server start

5. 登录测试：

[root@db_server_yayun_01 ~]# clickhouse-client 
ClickHouse client version 1.1.54198.
Connecting to localhost:9000.
Connected to ClickHouse server version 1.1.54198.

:) select 1

SELECT 1

┌─1─┐
│ 1 │
└───┘
→ Progress: 1.00 rows, 1.00 B (64.77 rows/s., 64.77 B/s.) 
1 rows in set. Elapsed: 0.016 sec. 

:) select now();

SELECT now()

┌───────────────now()─┐
│ 2017-03-31 15:14:18 │
└─────────────────────┘
↘ Progress: 1.00 rows, 1.00 B (216.22 rows/s., 216.22 B/s.) 
1 rows in set. Elapsed: 0.005 sec. 

:) 

启动失败可以查看日志，日志的目录默认为

/var/log/clickhouse-server

[root@db_server_yayun_01 clickhouse-server]# ll
total 16
-rw-rw-rw-. 1 clickhouse clickhouse  383 Mar 31 13:33 clickhouse-server.err.log
-rw-rw-rw-. 1 clickhouse clickhouse 7733 Mar 31 15:14 clickhouse-server.log
-rw-rw-rw-. 1 clickhouse clickhouse  138 Mar 31 13:33 stderr
-rw-rw-rw-. 1 clickhouse clickhouse    0 Mar 31 13:33 stdout
[root@db_server_yayun_01 clickhouse-server]# 

下面说说clickhouse-client的简单使用：

交互模式

clickhouse-client
clickhouse-client --host=... --port=... --user=... --password=...

启用多行查询：

clickhouse-client -m
clickhouse-client --multiline

对于建表的时候就需要启用多行查询，否则会报错，比如建如下表：

CREATE TABLE `ontime` (
  `Year` UInt16,
  `Quarter` UInt8,
  `Month` UInt8,
  `DayofMonth` UInt8,
  `DayOfWeek` UInt8,
  `FlightDate` Date,
  `UniqueCarrier` FixedString(7),
  `AirlineID` Int32,
  `Carrier` FixedString(2),
  `TailNum` String,
  `FlightNum` String,
  `OriginAirportID` Int32,
  `OriginAirportSeqID` Int32,
  `OriginCityMarketID` Int32,
  `Origin` FixedString(5),
  `OriginCityName` String,
  `OriginState` FixedString(2),
  `OriginStateFips` String,
  `OriginStateName` String,
  `OriginWac` Int32,
  `DestAirportID` Int32,
  `DestAirportSeqID` Int32,
  `DestCityMarketID` Int32,
  `Dest` FixedString(5),
  `DestCityName` String,
  `DestState` FixedString(2),
  `DestStateFips` String,
  `DestStateName` String,
  `DestWac` Int32,
  `CRSDepTime` Int32,
  `DepTime` Int32,
  `DepDelay` Int32,
  `DepDelayMinutes` Int32,
  `DepDel15` Int32,
  `DepartureDelayGroups` String,
  `DepTimeBlk` String,
  `TaxiOut` Int32,
  `WheelsOff` Int32,
  `WheelsOn` Int32,
  `TaxiIn` Int32,
  `CRSArrTime` Int32,
  `ArrTime` Int32,
  `ArrDelay` Int32,
  `ArrDelayMinutes` Int32,
  `ArrDel15` Int32,
  `ArrivalDelayGroups` Int32,
  `ArrTimeBlk` String,
  `Cancelled` UInt8,
  `CancellationCode` FixedString(1),
  `Diverted` UInt8,
  `CRSElapsedTime` Int32,
  `ActualElapsedTime` Int32,
  `AirTime` Int32,
  `Flights` Int32,
  `Distance` Int32,
  `DistanceGroup` UInt8,
  `CarrierDelay` Int32,
  `WeatherDelay` Int32,
  `NASDelay` Int32,
  `SecurityDelay` Int32,
  `LateAircraftDelay` Int32,
  `FirstDepTime` String,
  `TotalAddGTime` String,
  `LongestAddGTime` String,
  `DivAirportLandings` String,
  `DivReachedDest` String,
  `DivActualElapsedTime` String,
  `DivArrDelay` String,
  `DivDistance` String,
  `Div1Airport` String,
  `Div1AirportID` Int32,
  `Div1AirportSeqID` Int32,
  `Div1WheelsOn` String,
  `Div1TotalGTime` String,
  `Div1LongestGTime` String,
  `Div1WheelsOff` String,
  `Div1TailNum` String,
  `Div2Airport` String,
  `Div2AirportID` Int32,
  `Div2AirportSeqID` Int32,
  `Div2WheelsOn` String,
  `Div2TotalGTime` String,
  `Div2LongestGTime` String,
  `Div2WheelsOff` String,
  `Div2TailNum` String,
  `Div3Airport` String,
  `Div3AirportID` Int32,
  `Div3AirportSeqID` Int32,
  `Div3WheelsOn` String,
  `Div3TotalGTime` String,
  `Div3LongestGTime` String,
  `Div3WheelsOff` String,
  `Div3TailNum` String,
  `Div4Airport` String,
  `Div4AirportID` Int32,
  `Div4AirportSeqID` Int32,
  `Div4WheelsOn` String,
  `Div4TotalGTime` String,
  `Div4LongestGTime` String,
  `Div4WheelsOff` String,
  `Div4TailNum` String,
  `Div5Airport` String,
  `Div5AirportID` Int32,
  `Div5AirportSeqID` Int32,
  `Div5WheelsOn` String,
  `Div5TotalGTime` String,
  `Div5LongestGTime` String,
  `Div5WheelsOff` String,
  `Div5TailNum` String
) ENGINE = MergeTree(FlightDate, (Year, FlightDate), 8192)

以批处理方式运行查询：

clickhouse-client --query='SELECT 1'
echo 'SELECT 1' | clickhouse-client

从指定格式的文件插入数据：

clickhouse-client --query='INSERT INTO table VALUES' < data.txt
clickhouse-client --query='INSERT INTO table FORMAT TabSeparated' < data.tsv

参考资料：

https://github.com/redsoftbiz/clickhouse-rpm

https://clickhouse.yandex/