openGauss每日一练第21天 | 行存和列存

openGauss每日一练第21天 | 行存和列存

学习目标

学习openGauss存储模型-行存和列存

行存储是指将表按行存储到硬盘分区上，列存储是指将表按列存储到硬盘分区上。默认情况下，创建的表为行存储。

行、列存储模型各有优劣，通常用于TP场景的数据库，默认使用行存储，仅对执行复杂查询且数据量大的AP场景时，才使用列存储

课程学习

连接数据库

#第一次进入等待15秒#数据库启动中...

su - omm

gsql -r

1.创建行存表

CREATE TABLE test_t1

(

col1 CHAR(2),

col2 VARCHAR2(40),

col3 NUMBER

);

–压缩属性为no

\d+ test_t1

insert into test_t1 select col1, col2, col3 from (select generate_series(1, 100000) as key, repeat(chr(int4(random() * 26) + 65), 2) as  col1, repeat(chr(int4(random() * 26) + 65), 30) as  col2, (random() * (10^4))::integer as col3);

2.创建列存表

CREATE TABLE test_t2

(

col1 CHAR(2),

col2 VARCHAR2(40),

col3 NUMBER

)

WITH (ORIENTATION = COLUMN);

–压缩属性为low

\d+ test_t2;

–插入和行存表相同的数据

insert into test_t2 select * from test_t1;

3.占用空间对比

\d+

4.对比读取一列的速度

analyze VERBOSE test_t1;

analyze VERBOSE test_t2;

–列存表时间少于行存表

explain analyze select distinct col1 from test_t1;

explain analyze select distinct col1 from test_t2;

5.对比插入一行的速度

–行存表时间少于列存表

explain analyze insert into test_t1 values('x', 'xxxx', '123');

explain analyze insert into test_t2 values('x', 'xxxx', '123');

6.清理数据

drop table test_t1;

drop table test_t2;

课程作业

1.创建行存表和列存表，并批量插入10万条数据(行存表和列存表数据相同)

CREATE TABLE t1 ( col1 CHAR(2), col2 VARCHAR2(40), col3 NUMBER );

\d+ t1

insert into t1 select col1, col2, col3 from (select generate_series(1, 100000) as key, repeat(chr(int4(random() * 26) + 65), 2) as col1, repeat(chr(int4(random() * 26) + 65), 30) as col2, (random() * (10^4))::integer as col3);

CREATE TABLE t2 ( col1 CHAR(2), col2 VARCHAR2(40), col3 NUMBER ) WITH (ORIENTATION = COLUMN);

\d+ t2

insert into t2 select * from t1;

2. 对比行存表和列存表空间大小

3. 对比查询一列和插入一行的速度

analyze VERBOSE t1;

analyze VERBOSE t2;

explain analyze insert into t1 values('s', 'ssss', '123');

explain analyze insert into t2 values('s', 'ssss', '123');

4. 清理数据

drop table t1;

drop table t2;