使用rds_superuser登陆需要安装pg_hint_plan插件的数据库。
postgres=> \du+
List of roles
Role name | Attributes | Member of | Description
--------------+------------------------------------------------+-----------+---------------
digoal | | {} | rds_superuser
postgres=> \c test执行以下SQL：
test=> create extension pg_hint_plan;
CREATE EXTENSION修改所有用户的session_preload_libraries
test=> alter role all set session_preload_libraries='pg_hint_plan';
ALTER ROLE试用pg_hint_plan
test=> create table test(id int primary key, info text);
CREATE TABLE
test=> insert into test select generate_series(1,100000);
INSERT 0 100000
test=> explain select * from test where id=1;
QUERY PLAN
-----------------------------------------------------------------------
Index Scan using test_pkey on test (cost=0.29..8.31 rows=1 width=36)
Index Cond: (id = 1)
(2 rows)
test=> /*+ seqscan(test) */ explain select * from test where id=1;
QUERY PLAN
----------------------------------------------------------
Seq Scan on test (cost=0.00..1124.11 rows=272 width=36)
Filter: (id = 1)
(2 rows)
test=> /*+ bitmapscan(test) */ explain select * from test where id=1;
QUERY PLAN
------------------------------------------------------------------------
Bitmap Heap Scan on test (cost=4.30..8.31 rows=1 width=36)
Recheck Cond: (id = 1)
-> Bitmap Index Scan on test_pkey (cost=0.00..4.30 rows=1 width=0)
Index Cond: (id = 1)
(4 rows)
