openGuass每日一练第17天|学习心得体会

课程学习内容

软件版本 ：openGauss 3.0.0

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。

数据库实操内容

环境准备

–为表test的testnum列创建一个索引

su - omm

gsql -r

drop table if exists test;

create table test(id serial primary key,testnum serial);

create index idx_test_testnum on test(testnum);

–查看索引

\di

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
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=# \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)

omm=# 

通过hint使用索引

–测试准备，创建表customer，并插入数据

CREATE TABLE customer (

ca_address_sk integer NOT NULL ,

ca_address_id character(16),

ca_street_number character(10) ,

ca_street_name character varying(60) ,

ca_street_type character(15) ,

ca_suite_number character(10) ,

ca_city character varying(60) ,

ca_county character varying(30) ,

ca_state character(2) ,

ca_zip character(10) ,

ca_country character varying(20) ,

ca_gmt_offset numeric(5,2) ,

ca_location_type character(20)

);

insert into customer values

(1, ‘AAAAAAAABAAAAAAA’, ‘18’, ‘Jackson’, ‘Parkway’, ‘Suite 280’, ‘Fairfield’, ‘Maricopa County’, ‘AZ’, ‘86192’ ,‘United States’, -7.00, ‘condo’),

(2, ‘AAAAAAAACAAAAAAA’, ‘362’, ‘Washington 6th’, ‘RD’, ‘Suite 80’, ‘Fairview’, ‘Taos County’, ‘NM’, ‘85709’, ‘United States’, -7.00, ‘condo’),

(3, ‘AAAAAAAADAAAAAAA’, ‘585’, ‘Dogwood Washington’, ‘Circle’, ‘Suite Q’, ‘Pleasant Valley’, ‘York County’, ‘PA’, ‘12477’, ‘United States’, -5.00, ‘single family’);

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(# 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=# 

–创建索引

create index customer_idx on customer(ca_address_sk);

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

EXPLAIN SELECT /*+ indexscan(customer customer_idx ) */ * FROM customer WHERE ca_address_sk<100;

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=# 

rename索引

ALTER INDEX idx_test_testnum RENAME TO idx_test_testnum_new;

omm=# ALTER INDEX idx_test_testnum RENAME TO idx_test_testnum_new;
ALTER INDEX
omm=# 

重建索引

–重建一个单独索引

ALTER INDEX idx_test_testnum_new REBUILD;

REINDEX INDEX idx_test_testnum_new;

omm=# ALTER INDEX  idx_test_testnum_new REBUILD;
REINDEX
omm=# REINDEX INDEX  idx_test_testnum_new;
REINDEX
omm=# 

–重建所有索引

reindex table test;

omm=# reindex table test;
REINDEX
omm=# 

移动索引到其他表空间

–创建表空间myindex_ts：

CREATE TABLESPACE myindex_ts RELATIVE LOCATION ‘tablespace/myindex_ts1’;

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：

ALTER INDEX idx_test_testnum_new SET TABLESPACE myindex_ts;

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=#  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 myindex_ts
(2 rows)

omm=# 
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 myindex_ts
(1 row)

omm=# 

删除索引

–执行下面的命令，删除表test上的索引idx_test_testnum_new：

drop index idx_test_testnum_new;

omm=# drop index idx_test_testnum_new;
DROP INDEX
omm=# 

课程作业

创建表，在表中创建索引

omm=# create table test1(id serial primary key,testnum serial);
NOTICE:  CREATE TABLE will create implicit sequence "test1_id_seq" for serial column "test1.id"
NOTICE:  CREATE TABLE will create implicit sequence "test1_testnum_seq" for serial column "test1.testnum"
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test1_pkey" for table "test1"
CREATE TABLE
omm=# create index idx_test_testnum1 on test(testnum);
CREATE INDEX
omm=# CREATE TABLE customer1
omm-# (
omm(# ca_address_id character(16),
omm(# ca_address_sk integer NOT NULL ,
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 customer1 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=# 
omm=# create index customer_idx1 on  customer1(ca_address_sk);
CREATE INDEX
omm=# 

通过hint使用索引

omm=# EXPLAIN SELECT /*+ indexscan(customer1 customer_idx1 ) */ 
omm-#  * FROM customer1 WHERE ca_address_sk<100;
                                   QUERY PLAN                                    
---------------------------------------------------------------------------------
 [Bypass]
   Index Scan using customer_idx1 on customer1  (cost=0.00..8.27 rows=1 width=788)
   Index Cond: (ca_address_sk < 100)
(3 rows)

omm=#

rename索引

omm=# ALTER INDEX idx_test_testnum1 RENAME TO idx_test_testnum_1;
ALTER INDEX

重建索引

omm=# ALTER INDEX  idx_test_testnum_1 REBUILD;
REINDEX
omm=# 
omm=# REINDEX INDEX  idx_test_testnum_1;
REINDEX
omm=# 

移动索引到其他表空间

omm=#  CREATE TABLESPACE myindex_ts1 RELATIVE LOCATION 'tablespace/myindex_ts11';
CREATE TABLESPACE
omm=# ALTER INDEX idx_test_testnum_1 SET TABLESPACE myindex_ts1;
ALTER INDEX
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_1 | myindex_ts1 | CREATE INDEX idx_test_testnum_1 ON test USING btree (t
estnum) TABLESPACE myindex_ts1
(2 rows)

omm=# select * from pg_indexes where indexname = 'idx_test_testnum_1';
 schemaname | tablename |     indexname      | tablespace  |                                       indexdef        
                               
------------+-----------+--------------------+-------------+-------------------------------------------------------
-------------------------------
 public     | test      | idx_test_testnum_1 | myindex_ts1 | CREATE INDEX idx_test_testnum_1 ON test USING btree (t
estnum) TABLESPACE myindex_ts1
(1 row)

omm=# 

删除索引

omm=# drop index idx_test_testnum_1;
DROP INDEX
omm=# 

课程学习体会

​ 通过本次的实训操作，掌握数据库的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。。