Commands frequently used in postgresql database DBA operation and maintenance

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Commands frequently used in postgresql database DBA operation and maintenance

(Continuous update)
Recently, I have been maintaining the postgresql database, and sort out the frequently used commands and sql statements.
postgresql11 common commands
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1. Deadlock

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Because of postgresql itself, some tables are often locked

1. Query lock

select w1.pid as 等待进程,
w1.mode as 等待锁模式,
w2.usename as 等待用户,
w2.query as 等待会话,
b1.pid as 锁的进程,
b1.mode 锁的锁模式,
b2.usename as 锁的用户,
b2.query as 锁的会话,
b2.application_name 锁的应用,
b2.client_addr 锁的IP地址,
b2.query_start 锁的语句执行时间
from pg_locks w1
join pg_stat_activity w2 on w1.pid=w2.pid
join pg_locks b1 on w1.transactionid=b1.transactionid and w1.pid!=b1.pid
join pg_stat_activity b2 on b1.pid=b2.pid
where not w1.granted;

2. Kill the deadlock process

SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE pid='62560'

If you still cannot kill the session, you can kill it directly at the operating system level

2. View the running process

Used for server monitoring, process can be queried, time consumption is related to lock

SELECT 
C.relname 对象名称,
l.locktype 可锁对象的类型,
l.pid 进程id,
l.MODE 持有的锁模式,
l.GRANTED 是否已经对锁进行授权,
l.fastpath,
psa.datname 数据库名称,
psa.usesysid 用户id,
psa.usename 用户名称,
psa.application_name 应用程序名称,
psa.client_addr 连接的IP地址,
psa.client_port 连接使用的TCP端口号,
psa.backend_start 进程开始时间,
psa.xact_start 事务开始时间,
psa.query_start 事务执行此语句时间,
psa.state_change 事务状态改变时间,
psa.wait_event_type 等待事件类型,
psa.wait_event 等待事件,
psa.STATE 查询状态,
backend_xid 事务是否有写入操作,
backend_xmin 是否执事务快照,
psa.query 执行语句,
now( ) - query_start 持续时间
FROM
pg_locks l
INNER JOIN pg_stat_activity psa ON ( psa.pid = l.pid )
LEFT OUTER JOIN pg_class C ON ( l.relation = C.oid )
-- where l.relation = 'tb_base_apparatus'::regclass
where relkind ='r'
ORDER BY query_start asc

Three PostgreSql query database, index, table, table space size

-Query table space size

select pg_size_pretty(pg_tablespace_size('pg_default'));

-Query the size of all databases

 select pg_database.datname, pg_size_pretty(pg_database_size(pg_database.datname)) AS size from pg_databas;

-Query the specified index size

select pg_size_pretty(pg_relation_size('dotime'));

-Query the size of all indexes of the specified table

select pg_size_pretty(pg_indexes_size('tb_sys_loginfo'));

– Query the size of all indexes in the specified schema, sorted in descending order.

 select relname,indexrelname, pg_size_pretty(pg_relation_size(relid)) from pg_stat_user_indexes where schemaname='public' order by pg_relation_size(relid) desc;

-Query the specified table size (only specified table data)

 select pg_size_pretty(pg_relation_size('tb_sys_loginfo'));

-Query the total size of the specified table (including table data and indexes)

select pg_size_pretty(pg_total_relation_size('tb_sys_loginfo'));

-Query the size of all tables in the specified schema (only specified table data, from large to small)

select relname, pg_size_pretty(pg_relation_size(relid)) from pg_stat_user_tables where schemaname='public' order by pg_relation_size(relid) desc;

-Query the data size, total index size, total size, number of rows in all tables in the specified schema

SELECT
    table_size.relname 表名,
    pg_size_pretty ( pg_relation_size ( relid ) ) 表数据大小,
    pg_size_pretty ( pg_indexes_size ( relid ) ) 表总索引大小,
    pg_size_pretty ( pg_total_relation_size ( relid ) ) 表总大小,
    表行数
FROM
pg_stat_user_tables table_size
    LEFT JOIN (
        SELECT
            relname,
            reltuples :: DECIMAL ( 19, 0 ) 表行数
        FROM
        pg_class r
        JOIN pg_namespace n ON ( relnamespace = n.oid )
        WHERE
            relkind = 'r'
            AND n.nspname = 'public'
        ) table_num ON table_num.relname = table_size.relname
WHERE
    schemaname = 'public'
ORDER BY
    pg_relation_size ( relid ) DESC;

Four query external server

select * from pg_foreign_server;

Five kills all database connections

SELECT
    pg_terminate_backend(pid)
FROM
    pg_stat_activity
WHERE
    -- don't kill my own connection
    pid <> pg_backend_pid()
    -- don't kill the connections to other databases
    AND datname = '库名'
    ;

Six restart the service

--启动服务：
systemctl start postgresql-11
--停止服务：
systemctl stop postgresql-11
--重启服务：
systemctl restart postgresql-11
--查看pgagent_11服务
systemctl enable pgagent_11
systemctl status pgagent_11
systemctl start pgagent_11

Seven backup and restore

1. Back up the database

pg_dump --file "/home/back/pgsql-all-"$(date +%F+%T)".backup" --host "0.0.0.11" --port "5432" --username "postgres" --dbname "postgres" --verbose --role "postgres" --format=c --blobs --encoding "UTF8"

2. Restore the database

pg_restore --username "postgres" --no-password --role "postgres" --dbname "hrmwv2" --verbose /home/back/pgsql-all-postgres-2020-07-22+11:03:28.backup

There are three ways to reload the database configuration:

1. Run as super user

postgres=# SELECT pg_reload_conf();

2. Use UNIX kill to manually initiate HUP signals

$kill -HUP PID

3. Use the pg_ctl command to trigger the SIGHUP signal

$pg_ctl reload