openGauss每日一练第9天 | 索引学习

学习openGauss普通表索引

索引是对数据库表中一列或多列的值进行排序的一种结构，使用索引可快速访问数据库表中的特定信息

课程学习

#第一次进入等待15秒
#数据库启动中...
su - omm
gsql -r

1.创建索引

create schema tpcds;
CREATE TABLE tpcds.ship_mode_t1
(
SM_SHIP_MODE_SK INTEGER NOT NULL,
SM_SHIP_MODE_ID CHAR(16) NOT NULL,
SM_TYPE CHAR(30),
SM_CODE CHAR(10),
SM_CARRIER CHAR(20),
SM_CONTRACT CHAR(20)
);

– SM_SHIP_MODE_SK字段上创建普通的唯一索引

CREATE UNIQUE INDEX ds_ship_mode_t1_index1 ON tpcds.ship_mode_t1(SM_SHIP_MODE_SK);

– SM_SHIP_MODE_SK字段上创建指定B-tree索引。

CREATE INDEX ds_ship_mode_t1_index4 ON tpcds.ship_mode_t1 USING btree(SM_SHIP_MODE_SK);

–SM_CODE字段上创建表达式索引

CREATE INDEX ds_ship_mode_t1_index2 ON tpcds.ship_mode_t1(SUBSTR(SM_CODE,1 ,4));

– SM_SHIP_MODE_SK字段上创建SM_SHIP_MODE_SK大于10的部分索引

CREATE UNIQUE INDEX ds_ship_mode_t1_index3 ON tpcds.ship_mode_t1(SM_SHIP_MODE_SK) WHERE SM_SHIP_MODE_SK>10;

–查看表信息

\d+ tpcds.ship_mode_t1

–查看系统视图pg_indexes

select * from pg_indexes where tablename = 'ship_mode_t1';

2.修改索引定义

–重命名索引

ALTER INDEX tpcds.ds_ship_mode_t1_index1 RENAME TO ds_ship_mode_t1_index5;

–设置索引不可用

ALTER INDEX tpcds.ds_ship_mode_t1_index2 UNUSABLE;

–修改索引表空间

CREATE TABLESPACE example0 RELATIVE LOCATION 'tablespace1/tablespace_0';
alter index tpcds.ds_ship_mode_t1_index4 set tablespace example0;
\d+ tpcds.ship_mode_t1;

3.重建索引

–重建一个单独索引

ALTER INDEX tpcds.ds_ship_mode_t1_index2 REBUILD;
REINDEX INDEX tpcds.ds_ship_mode_t1_index4;

–重建所有索引

reindex table tpcds.ship_mode_t1;

4.删除索引

DROP INDEX tpcds.ds_ship_mode_t1_index2;
DROP INDEX tpcds.ds_ship_mode_t1_index3;
DROP INDEX tpcds.ds_ship_mode_t1_index4;
DROP INDEX tpcds.ds_ship_mode_t1_index5;

课程作业

1.创建表products, 分别为表创建一个unique索引1，指定b-tree索引2和表达式索引3

CREATE TABLE tpcds.products
(
id INTEGER NOT NULL,
name CHAR(16) NOT NULL,
category CHAR(30),
price DECIMAL(5,2)
);
CREATE UNIQUE INDEX tpcds.products_index1 ON tpcds.products(id);
CREATE INDEX tpcds.products_index2 ON tpcds.products USING btree(name);
CREATE INDEX tpcds.products_index3 ON tpcds.products(SUBSTR(category,1 ,4));

2.设置索引1不可用，修改索引2的表空间，重命名索引3

alter index tpcds.products_index1 unusable;
CREATE TABLESPACE example1 RELATIVE LOCATION 'tablespace1/tablespace_1';
alter index tpcds.products_index2 set tablespace example1;
\d+ tpcds.products_index2;
alter index tpcds.products_index3 rename to products_index4;

3.重建索引2和products的所有索引

alter index tpcds.products_index2 rebuild;
reindex index tpcds.products_index2;
reindex table tpcds.products;

4.使用\d+和系统视图pg_indexes查看索引信息

\d+ tpcds.products
select * from pg_indexes where tablename='products';

5.删除索引、表和表空间

drop index tpcds.products_index1;
drop index tpcds.products_index2;
drop index  tpcds.products_index4;
drop table tpcds.products;
drop tablespace example1;