Docs: Overview

Wed, 20 Mar 2024 13:35:28 +0800

简要概述

TODO;

Docs: Merge Tree

Sun, 24 Mar 2024 14:42:51 +0800

简要概述

合并树表引擎。

创建表

语法

CREATE TABLE [IF NOT EXISTS] [db.]table_name [ON CLUSTER cluster]
(
 name1 [type1] [[NOT] NULL] [DEFAULT|MATERIALIZED|ALIAS|EPHEMERAL expr1] [COMMENT ...] [CODEC(codec1)] [STATISTIC(stat1)] [TTL expr1] [PRIMARY KEY] [SETTINGS (name = value, ...)],
 name2 [type2] [[NOT] NULL] [DEFAULT|MATERIALIZED|ALIAS|EPHEMERAL expr2] [COMMENT ...] [CODEC(codec2)] [STATISTIC(stat2)] [TTL expr2] [PRIMARY KEY] [SETTINGS (name = value, ...)],
 ...
 INDEX index_name1 expr1 TYPE type1(...) [GRANULARITY value1],
 INDEX index_name2 expr2 TYPE type2(...) [GRANULARITY value2],
 ...
 PROJECTION projection_name_1 (SELECT <COLUMN LIST EXPR> [GROUP BY] [ORDER BY]),
 PROJECTION projection_name_2 (SELECT <COLUMN LIST EXPR> [GROUP BY] [ORDER BY])
) ENGINE = MergeTree()
ORDER BY expr
[PARTITION BY expr]
[PRIMARY KEY expr]
[SAMPLE BY expr]
[TTL expr
 [DELETE|TO DISK 'xxx'|TO VOLUME 'xxx' [, ...] ]
 [WHERE conditions]
 [GROUP BY key_expr [SET v1 = aggr_func(v1) [, v2 = aggr_func(v2) ...]] ] ]
[SETTINGS name = value, ...]

示例

CREATE TABLE test.hosts
(
 `start_time` DateTime,
 `host` String,
 `status` UInt32,
) ENGINE = MergeTree() order by start_time;

存储结构

系统上的路径

这里以 rpm 安装后默认存储路径为 “/var/lib/clickhouse/"，其中数据库 “test” 下的 “hosts” 表为例：

在系统上的存储路径为："/var/lib/clickhouse/data/test/hosts”

数据分区规则

类型	分区表达式	示例数据	分区ID
无	无	-	all
数字	PARTITION BY status	200, 400	分区1：200、分区2：400
日期	PARTITION BY start_time	2024-03-24	分区1：2024-03-24
字符串	PARTITION BY host	example.com	分区1：md5sum(host)

OPSaid – ClickHouse

Docs: Overview

简要概述

Docs: Merge Tree

简要概述

创建表

语法

示例

存储结构

系统上的路径

数据分区规则