PostgreSQL常用脚本整理

1、序列

以自增serial类型主键的序列：

alter sequence s_seq restart with 1;　　#重置序列
select currval('tablename_pid_seq');
select nextval('tablename_pid_seq');
select setval('tablename_pid_seq',1);

2、修改表

--删除约束
alter table tablename alter column col drop not null;

--添加约束
alter table tablename add constraint tablename_col_uq unique(col);

--修改类型/长度
alter table tablename alter column col type character varying(2000);

--添加列
alter table tablename add column col character varying(255);

--删除列
alter table tablename drop column col;

3、查看数据使用空间

select pg_size_pretty(pg_database_size('dbname'));

4、优化与监控

#查看数据库
select * from pg_stat_database

#查看链接情况
select * from pg_stat_activity where datname = 't0pagped'

select count(1) from pg_stat_activity;

#根据IP地址汇总连接数

select client_addr,count(client_addr) as num from pg_stat_activity
where datname = 't0pagped' and application_name = 'PostgreSQL JDBC Driver'
group by client_addr
order by num desc

#最大连接数
show max_connections;

#查看表使用情况
select * from pg_stat_user_tables where relname = 'kg_askbob_entity_ins_capital' order by seq_scan desc

#查看表索引
select * from pg_stat_user_indexes where relname = 'kg_askbob_entity_ins_capital'

PostgreSQL统计信息：

https://yq.aliyun.com/articles/697692