SQL语句
1.1. 查询表和索引的大小
SELECT
pretty_sizes. TABLE_NAME,
pg_size_pretty (table_size) AS table_size,
pg_size_pretty (indexes_size) AS indexes_size,
pg_size_pretty (total_size) AS total_size,
pretty_sizes.reltuples AS COUNT,
pretty_sizes.relpages
FROM
(
SELECT
all_tables. TABLE_NAME,
pg_table_size (all_tables. TABLE_NAME) AS table_size,
pg_indexes_size (all_tables. TABLE_NAME) AS indexes_size,
pg_total_relation_size (all_tables. TABLE_NAME) AS total_size,
table_size.reltuples,
table_size.relname,
table_size.relpages
FROM
(
SELECT
(
'"' || table_schema || '"."' || TABLE_NAME || '"'
) AS TABLE_NAME, TABLE_NAME as tmp_name
FROM
information_schema.tables
) AS all_tables
LEFT JOIN (
SELECT
relname AS TABLE_NAME,relname,relpages,reltuples
FROM
pg_class
WHERE
relkind = 'r'
) AS table_size ON (
table_size."table_name" = all_tables."tmp_name"
)
ORDER BY
total_size DESC
) AS pretty_sizes
1.2. 系统表
系统表介绍
pg_locks 保存锁的信息
pg_stat_activity 保存当前连接的信息
pg_stat_replication 保存复制状态信息
pg_stat_all_tables 包含所有表信息（user表和系统表）
pg_stat_sys_tables 包含系统表信息
pg_stat_user_tables 用户表，包含vacuum相关信息和数据库update/delete相关信息
pg_stat_all/sys/user_tables 全部索引，系统表的索引，用户表的索引
pg_stat_database 每个数据库中增删改查、提交，回滚，冲突的数量统计，以数据库为单位。
pg_stat_bgwriter checkpoint相关信息
pg_stat_database_conflicts 数据库冲突信息的统计（死锁，冲突），以数据库为单位
常用sql语句
l 查询前10大的表
select relname,relpages from pg_class order by relpages desc limit 10;
l 查询对应数据库的活跃连接
select * from pg_stat_activity where datname='testdb';
l 查询活跃连接在执行的任务
select client_addr, query_start,query from pg_stat_activity;
l 关闭该数据库的活跃连接，但是自己不能关闭自己
select pg_terminate_backend(pid) from pg_stat_activity where datname='testdb' and pid <> pg_backend_pid();
l 查询当前事物ID
select txid_current();
l 查看oid和磁盘页的数量
select oid,relpages from pg_class where relname='test';
l 查询某个oid对应的信息
select * from pg_database where oid='16385';
l 查看某个oid对应的磁盘文件路径
select pg_relation_filepath(16392);
select pg_relation_filepath(oid),relpages from pg_class where relname = 'test1';
l 查询某个表的oid（oid可以理解为唯一标示，其作为这个表/库的文件夹名,在data目录可以找到的）
select oid,* from pg_class where relname = 'gctest';
l 查询某个表的磁盘文件，及页的数量
select pg_relation_filepath(oid),relpages from pg_class where relname = 'test';
l 查询占用磁盘页数最大的表
select relname,relpages from pg_class order by relpages desc limit 10;
l 查询某个表的大小
select pg_size_pretty(pg_relation_size('xxxx'));
l 查询某个库的oid
SELECT oid from pg_database where datname='testdb';
l 查看库大小
select pg_database.datname, pg_size_pretty(pg_database_size(pg_database.datname)) AS size from pg_database;
1.3. psql查询语句
|
指令 |
作用 |
|
di+ |
显示所有的索引及索引的大小 |
|
l+ |
列出所有数据库、大小、权限信息 |
|
dn+ |
列出schema对应用户的权限 |
|
dp+ |
列出表、视图对应用户的权限 |
|
x |
设置查询结果为列式展示，再设置一次复原行级展示 |
|
c dbname |
切换数据库 |
1.4. 用户相关sql
l 用户操作
create user test with password 'test'; 创建用户
drop user test; 删除用户
alter user test superuser; 修改用户为超级用户
alter user test password '123456'; 修改用户的密码
l 用户权限
grant select on all tables in schema public to admin; 当前数据库的所有查询权限
revoke select on all tables in schema public from admin;
grant connect on database testdb to admin;
grant all on table test to admin; 赋予test表的所有权限给admin用户
revoke all on table test from admin; 回收权限
grant all privileges on database testdb to admin;
将数据库testdb的所有权限赋予用户admin
revoke all privileges on database testdb from admin; 回收权限
select * from pg_roles; 查询角色
1.5. 表操作
l 创建数据库
CREATE DATABASE exampledb OWNER dbuser;
l 创建表
l CREATE TABLE gctest AS SELECT * FROM generate_series(1,100000); 创建含有10W行数据的表
create table test (id int);
create table collectinfo(id VARCHAR, username VARCHAR, update_time timestamp default current_timestamp, click_num int, finished boolean, primary key(id));
insert into test select generate_series(1,49);
l 修改表
alter table test add column name varchar; 增加列，列名为那么，表名为test
alter table test drop column name; 删除列
alter table test alter column name set default 'gc'; 列设置默认值
l 查询表中记录（行）的隐藏字段
select xmin,xmax,cmin,cmax,ctid,* from test;
l 分析查询语句
explain (analyze,verbose,timing,costs,buffers) select count(*) from test1;