openGauss每日一练第21天|存储模型-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(3),
col2 VARCHAR2(50),
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(3),
col2 VARCHAR2(50),
col3 NUMBER
)WITH (ORIENTATION = COLUMN);
insert into t2 select * from t1;

2.对比行存表和列存表空间大小

\d+

3.对比查询一列和插入一行的速度

analyze VERBOSE t1;
analyze VERBOSE t2;
explain analyze select distinct col1 from t1;
explain analyze select distinct col1 from t2;
explain analyze insert into t1 values('x', 'xxxx', '123');
explain analyze insert into t2 values('x', 'xxxx', '123');

4.清理数据

drop table t1 casecade;
drop table t2;