openGauss每日一练第9天|《学习openGauss普通表索引》学习心得体会和课后练习

openGauss每日一练第9天|《学习openGauss普通表索引》学习心得体会和课后练习

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);

– M_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
omm=# \d+ tpcds.ship_mode_t1
                             Table "tpcds.ship_mode_t1"
     Column      |     Type      | Modifiers | Storage  | Stats target | Description 
-----------------+---------------+-----------+----------+--------------+-------------
 sm_ship_mode_sk | integer       | not null  | plain    |              | 
 sm_ship_mode_id | character(16) | not null  | extended |              | 
 sm_type         | character(30) |           | extended |              | 
 sm_code         | character(10) |           | extended |              | 
 sm_carrier      | character(20) |           | extended |              | 
 sm_contract     | character(20) |           | extended |              | 
Indexes:
    "ds_ship_mode_t1_index1" UNIQUE, btree (sm_ship_mode_sk) TABLESPACE pg_default
    "ds_ship_mode_t1_index3" UNIQUE, btree (sm_ship_mode_sk) TABLESPACE pg_default WHERE sm_ship_mode_sk > 10
    "ds_ship_mode_t1_index2" btree (substr(sm_code::text, 1, 4)) TABLESPACE pg_default
    "ds_ship_mode_t1_index4" btree (sm_ship_mode_sk) TABLESPACE pg_default
Has OIDs: no
Options: orientation=row, compression=no

–查看系统视图pg_indexes

select * from pg_indexes where tablename = 'ship_mode_t1';
omm=# select * from pg_indexes where tablename = 'ship_mode_t1';
 schemaname |  tablename   |       indexname        | tablespace |                            
                                         indexdef                                             
                         
1_index2 ON tpcds.ship_mode_t1 USING btree (substr((sm_code)::text, 1, 4)) TABLESPACE pg_defau
lt
 tpcds      | ship_mode_t1 | ds_ship_mode_t1_index3 |            | CREATE UNIQUE INDEX ds_ship
_mode_t1_index3 ON tpcds.ship_mode_t1 USING btree (sm_ship_mode_sk) TABLESPACE pg_default WHER
E (sm_ship_mode_sk > 10)
(4 rows)

------------+--------------+------------------------+------------+----------------------------
----------------------------------------------------------------------------------------------
-------------------------
 tpcds      | ship_mode_t1 | ds_ship_mode_t1_index1 |            | CREATE UNIQUE INDEX ds_ship
_mode_t1_index1 ON tpcds.ship_mode_t1 USING btree (sm_ship_mode_sk) TABLESPACE pg_default
 tpcds      | ship_mode_t1 | ds_ship_mode_t1_index4 |            | CREATE INDEX ds_ship_mode_t
1_index4 ON tpcds.ship_mode_t1 USING btree (sm_ship_mode_sk) TABLESPACE pg_default
 tpcds      | ship_mode_t1 | ds_ship_mode_t1_index2 |            | CREATE INDEX ds_ship_mode_t
omm=# 

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 products(id int,name varchar2(20));

create unique index pro_idx_1 on products(id);
CREATE INDEX pro_idx_2 ON products USING btree(name);
create index pro_idx_3 on products(upper(name));

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 pro_idx_1 UNUSABLE;
alter index pro_idx_3 rename to pro_idx_3_new;
CREATE TABLESPACE new RELATIVE LOCATION 'tablespace1/new';
alter index pro_idx_2  set tablespace new;

omm=# \d+ products
                              Table "public.products"
 Column |         Type          | Modifiers | Storage  | Stats target | Description 
--------+-----------------------+-----------+----------+--------------+-------------
 id     | integer               |           | plain    |              | 
 name   | character varying(20) |           | extended |              | 
Indexes:
    "pro_idx_1" UNIQUE, btree (id) TABLESPACE pg_default
    "pro_idx_2" btree (name) TABLESPACE new, tablespace "new"
    "pro_idx_3_new" btree (upper(name::text)) TABLESPACE pg_default
Has OIDs: no
Options: orientation=row, compression=no

3.重建索引2和products的所有索引

alter INDEX pro_idx_2  rebuild;
reindex table products;

4.使用\d+和系统视图pg_indexes查看索引信息

\d+ products
select * from pg_indexes where relname='products'

5.删除索引、表和表空间

drop index pro_idx_1;
drop index pro_idx_2;
drop index pro_idx_3_new;
drop tablespace new;