openGauss每日一练第17天| openGauss逻辑结构：索引管理

1.创建表，在表中创建索引

--为表test的testnum列创建一个索引
root@modb:~# su - omm
omm@modb:~$ gsql -r
omm=# drop table if exists test;
omm=# create table test(id serial primary key,testnum serial);
omm=# create index idx_test_testnum on test(testnum);

--查看索引
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
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');

--创建索引

create index customer_idx on customer(ca_address_sk);

--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;
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)

3.rename索引

ALTER INDEX idx_test_testnum RENAME TO idx_test_testnum_new;

4.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;
--重建所有索引
reindex table test;

5.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';

--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;

--查看索引所在的表空间
select * from pg_indexes where tablename = 'test';
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
public | test | test_pkey | | CREATE UNIQUE INDEX test_pkey ON test USINGbtree (id) TABLESPACE pg_default
(2 rows)

--或
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)

6.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;