作者：马顺华
从事运维管理工作多年，目前就职于某科技有限公司，熟悉运维自动化、OceanBase部署运维、MySQL 运维以及各种云平台技术和产品。并已获得OceanBase认证OBCA、OBCP证书。
第17天 | openGauss逻辑结构：索引管理
学习目标
掌握openGauss DBMS索引的管理：创建索引、删除索引、查询索引的信息、修改索引的信息。
课程学习
索引是一个指向表中数据的指针。一个数据库中的索引与一本书的索引目录是非常相似的。
索引可以用来提高数据库查询性能，但是不恰当的使用将导致数据库性能下降。
1.创建索引
–为表test的testnum列创建一个索引
root@modb:~#
root@modb:~# su - omm
omm@modb:~$ gsql -r
gsql ((openGauss 3.0.0 build 02c14696) compiled at 2022-04-01 18:12:00 commit 0 last mr )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.
omm=# drop table if exists test;
NOTICE: table "test" does not exist, skipping
omm=# DROP TABLE
omm=# create table test(id serial primary key,testnum serial);
NOTICE: CREATE TABLE will create implicit sequence "test_id_seq" for serial column "test.id"
NOTICE: CREATE TABLE will create implicit sequence "test_testnum_seq" for serial column "test.testnum"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "test_pkey" for table "test"
CREATE TABLE
omm=# create index idx_test_testnum on test(testnum);
CREATE INDEX
omm=#
–查看索引
\di
omm=# \di
List of relations
Schema | Name | Type | Owner | Table | Storage
--------+------------------+-------+-------+-------+---------
public | idx_test_testnum | index | omm | test |
public | test_pkey | index | omm | test |
(2 rows)
2.通过hint使用索引
–测试准备，创建表customer，并插入数据
omm=# CREATE TABLE customer
omm-# (
omm(# ca_address_sk integer NOT NULL ,
omm(# ca_address_id character(16),
omm(# ca_street_number character(10) ,
omm(# ca_street_name character varying(60) ,
omm(# ca_street_type character(15) ,
omm(# ca_suite_number character(10) ,
omm(# ca_city character varying(60) ,
omm(# ca_county character varying(30) ,
omm(# ca_state character(2) ,
omm(# ca_zip character(10) ,
omm(# ca_country character varying(20) ,
omm(# omm(# ca_location_type character(20)
omm(# );ca_gmt_offset numeric(5,2) ,
CREATE TABLE
omm=#
omm=# insert into customer values
omm-# (1, 'AAAAAAAABAAAAAAA', '18', 'Jackson', 'Parkway', 'Suite 280', 'Fairfield', 'Maricopa County', 'AZ', '86192' ,'United States', -7.00, 'condo'),
omm-# (2, 'AAAAAAAACAAAAAAA', '362', 'Washington 6th', 'RD', 'Suite 80', 'Fairview', 'Taos County', 'NM', '85709', 'United States', -7.00, 'condo'),
omm-# (3, 'AAAAAAAADAAAAAAA', '585', 'Dogwood Washington', 'Circle', 'Suite Q', 'Pleasant Valley', 'York County', 'PA', '12477', 'United States', -5.00, 'single family');
omm=# INSERT 0 3
omm=#
–创建索引
omm=#
omm=# create index customer_idx on customer(ca_address_sk);
CREATE INDEX
omm=#
–通过hint强制使用索引，查看执行计划
omm=#
omm=# EXPLAIN SELECT /*+ indexscan(customer customer_idx ) */
omm-# * FROM customer WHERE ca_address_sk<100;
QUERY PLAN
-------------------------------------------------------------------------------
[Bypass]
Index Scan using customer_idx on customer (cost=0.00..8.27 rows=1 width=788)
Index Cond: (ca_address_sk < 100)
(3 rows)
omm=#
3.rename索引
omm=#
omm=# ALTER INDEX idx_test_testnum RENAME TO idx_test_testnum_new;
ALTER INDEX
omm=#
4.重建索引
–重建一个单独索引
omm=#
omm=# ALTER INDEX idx_test_testnum_new REBUILD;
REINDEX
omm=# REINDEX INDEX idx_test_testnum_new;
REINDEX
omm=#
–重建所有索引
omm=#
omm=# reindex table test;
REINDEX
omm=#
5.移动索引到其他表空间
–创建表空间myindex_ts：
omm=#
omm=# CREATE TABLESPACE myindex_ts RELATIVE LOCATION 'tablespace/myindex_ts1';
CREATE TABLESPACE
omm=#
–将索引idx_test_testnum_new移动到表空间myindex_ts：
omm=#
omm=# ALTER INDEX idx_test_testnum_new SET TABLESPACE myindex_ts;
ALTER INDEX
omm=#
–查看索引所在的表空间
select * from pg_indexes where tablename = ‘test’;
–或
select * from pg_indexes where indexname = ‘idx_test_testnum_new’;
omm=#
omm=# select * from pg_indexes where tablename = 'test';
schemaname | tablename | indexname | tablespace | indexdef
------------+-----------+----------------------+------------+--------------------------------------------------------------------------------
-------
public | test | test_pkey | | CREATE UNIQUE INDEX test_pkey ON test USING btree (id) TABLESPACE pg_default
public | test | idx_test_testnum_new | myindex_ts | CREATE INDEX idx_test_testnum_new ON test USING btree (testnum) TABLESPACE myin
dex_ts
(2 rows)
omm=# select * from pg_indexes where indexname = 'idx_test_testnum_new';
schemaname | tablename | indexname | tablespace | indexdef
------------+-----------+----------------------+------------+--------------------------------------------------------------------------------
-------
public | test | idx_test_testnum_new | myindex_ts | CREATE INDEX idx_test_testnum_new ON test USING btree (testnum) TABLESPACE myin
dex_ts
(1 row)
omm=#
5.删除索引
–执行下面的命令，删除表test上的索引idx_test_testnum_new：
omm=#
omm=# drop index idx_test_testnum_new;
DROP INDEX
omm=#
课程作业
1.创建表，在表中创建索引
2.通过hint使用索引
3.rename索引
4.重建索引
5.移动索引到其他表空间
6.删除索引
1.创建索引
–为表test的testnum列创建一个索引
root@modb:~#
root@modb:~# su - omm
omm@modb:~$ gsql -r
gsql ((openGauss 3.0.0 build 02c14696) compiled at 2022-04-01 18:12:00 commit 0 last mr )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.
omm=# drop table if exists my888;
NOTICE: table "my888" does not exist, skipping
DROP TABLE
omm=# create table my888(id serial primary key,my888num serial);
NOTICE: CREATE TABLE will create implicit sequence "my888_id_seq" for serial column "my888.id"
NOTICE: CREATE TABLE will create implicit sequence "my888_my888num_seq" for serial column "my888.my888num"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "my888_pkey" for table "my888"
CREATE TABLE
omm=# create index idx_my888_my888num on my888(my888num);
CREATE INDEX
omm=# \di
List of relations
Schema | Name | Type | Owner | Table | Storage
--------+--------------------+-------+-------+----------+---------
public | customer_idx | index | omm | customer |
public | idx_my888_my888num | index | omm | my888 |
public | my888_pkey | index | omm | my888 |
public | test_pkey | index | omm | test |
(4 rows)
omm=#
2.通过hint使用索引
omm=#
omm=# CREATE TABLE my666
omm-# (
omm(# ca_address_sk integer NOT NULL ,
omm(# ca_address_id character(16),
omm(# ca_street_number character(10) ,
omm(# ca_street_name character varying(60) ,
omm(# ca_street_type character(15) ,
omm(# ca_suite_number character(10) ,
omm(# ca_city character varying(60) ,
omm(# ca_county character varying(30) ,
omm(# ca_state character(2) ,
omm(# ca_zip character(10) ,
omm(# ca_country character varying(20) ,
omm(# ca_gmt_offset numeric(5,2) ,
omm(# ca_location_type character(20)
omm(# );
CREATE TABLE
omm=# insert into customer values
omm-# (1, 'AAAAAAAABAAAAAAA', '18', 'Jackson', 'Parkway', 'Suite 280', 'Fairfield', 'Maricopa County', 'AZ', '86192' ,'United States', -7.00, 'condo'),
omm-# (2, 'AAAAAAAACAAAAAAA', '362', 'Washington 6th', 'RD', 'Suite 80', 'Fairview', 'Taos County', 'NM', '85709', 'United States', -7.00, 'condo'),
omm-# (3, 'AAAAAAAADAAAAAAA', '585', 'Dogwood Washington', 'Circle', 'Suite Q', 'Pleasant Valley', 'York County', 'PA', '12477', 'United States', -5.00, 'single family');
INSERT 0 3
omm=# create index my666_idx on my666(ca_address_sk);
CREATE INDEX
omm=# EXPLAIN SELECT /*+ indexscan(my666 my666_idx ) */
omm-# * FROM my666 WHERE ca_address_sk<100;
QUERY PLAN
---------------------------------------------------------------------------
[Bypass]
Index Scan using my666_idx on my666 (cost=0.00..44.83 rows=33 width=788)
Index Cond: (ca_address_sk < 100)
(3 rows)
omm=#
3.rename索引
omm=# ALTER INDEX idx_my888_my888num RENAME TO idx_my888_my888num_new;
ALTER INDEX
omm=#
4.重建索引
omm=# ALTER INDEX idx_my888_my888num_new REBUILD;
REINDEX
omm=# REINDEX INDEX idx_my888_my888num_new;
REINDEX
omm=# reindex table my888;
REINDEX
omm=#
5.移动索引到其他表空间
omm=#
omm=# CREATE TABLESPACE openindex_ts RELATIVE LOCATION 'tablespace/openindex_ts1';
CREATE TABLESPACE
omm=# ALTER INDEX idx_my888_my888num_new SET TABLESPACE openindex_ts;
ALTER INDEX
omm=# select * from pg_indexes where tablename = 'my888';
schemaname | tablename | indexname | tablespace | indexdef
------------+-----------+------------------------+--------------+------------------------------------------------------------------------------------
---------
public | my888 | my888_pkey | | CREATE UNIQUE INDEX my888_pkey ON my888 USING btree (id) TABLESPACE pg_default
public | my888 | idx_my888_my888num_new | openindex_ts | CREATE INDEX idx_my888_my888num_new ON my888 USING btree (my888num) TABLESPACE open
index_ts
(2 rows)
omm=# select * from pg_indexes where indexname = 'idx_my888_my888num_new';
schemaname | tablename | indexname | tablespace | indexdef
------------+-----------+------------------------+--------------+------------------------------------------------------------------------------------
---------
public | my888 | idx_my888_my888num_new | openindex_ts | CREATE INDEX idx_my888_my888num_new ON my888 USING btree (my888num) TABLESPACE open
index_ts
(1 row)
omm=#
6.删除索引
–执行下面的命令，删除表test上的索引idx_my888_my888num_new：
omm=# drop index idx_my888_my888num_new;
DROP INDEX
omm=#
最后修改时间：2022-12-10 16:48:45
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