Greenplum is connected to the lock to view the data dictionary information

View system session / connection / SQL to the lock case

1, view the current active client connections

 SELECT count(*) FROM pg_stat_activity WHERE NOT pid=pg_backend_pid();   
 

2, check on the status of client connections  

SELECT pid,case when waiting='f' then 'already get lock,sql executing' when waiting='t' then 'waiting get lock,sql waiting execute' end lock_satus,
 current_timestamp - least(query_start,xact_start) AS runtime,substr(query,1,25) AS current_query
FROM pg_stat_activity

WHERE NOT pid=pg_backend_pid()

and state<>'idle'

and application_name<>'pg_statsinfod'

order by runtime desc

 

3, holding the lock and wait for the lock to view some information

--reltype=0代表其为索引
SELECT locker.pid,
        pc.relname,
        locker.mode,
        locker_act.application_name,
        least(query_start,xact_start) start_time,
        locker_act.state,
        CASE
    WHEN granted='f' THEN
    'wait_lock'
    WHEN granted='t' THEN
    'get_lock'
    END lock_satus,current_timestamp - least(query_start,xact_start) AS runtime,
 locker_act.query
FROM pg_locks locker,pg_stat_activity locker_act, pg_class pc
WHERE locker.pid=locker_act.pid
        AND NOT locker.pid=pg_backend_pid()
        AND application_name<>'pg_statsinfod'
        AND locker.relation = pc.oid
        AND pc.reltype<>0 --and pc.relname='t'
ORDER BY  runtime desc;

 

4, the query system is being executed or waiting transaction execution

--注意其只是代表事务信息，系统中也有可能存在慢的查询
select pc.relname lock_table,pc.oid,tans.pid, CASE
    WHEN waiting='f' THEN
    'already get lock,sql executing'
    WHEN waiting='t' THEN
    'waiting get lock,sql waiting execute'
    END lock_satus,
 least(query_start,xact_start) query_start,
 current_timestamp - least(query_start,xact_start) AS runtime,
 psa.query
from pg_locks tans,pg_locks pl,pg_class pc ,pg_stat_activity psa
where tans.transactionid is NOT null and pc.oid=pl.relation and tans.pid=pl.pid
and tans.pid=psa.pid and pc.reltype<>0
order by runtime desc;

 

sql and 5 lock_table information about your system by executing

SELECT locktype,
        pg_locks.pid,
         virtualtransaction,
         transactionid,
         nspname,
         relname,
         mode,
         granted,
    CASE
    WHEN granted='f' THEN
    'get_lock'
    WHEN granted='t' THEN
    'wait_lock'
    END lock_satus,
    CASE
    WHEN waiting='f' THEN
    'already get lock,sql executing'
    WHEN waiting='t' THEN
    'waiting get lock,sql waiting execute'
    END lock_satus,
 current_timestamp - least(query_start,xact_start) AS runtime,
 cast(date_trunc('second',query_start) AS timestamp) AS query_start, substr(query,1,25) AS query
FROM pg_locks LEFT OUTER
JOIN pg_class
    ON (pg_locks.relation = pg_class.oid) LEFT OUTER
JOIN pg_namespace
    ON (pg_namespace.oid = pg_class.relnamespace), pg_stat_activity
WHERE NOT pg_locks.pid=pg_backend_pid()
        AND pg_locks.pid=pg_stat_activity.pid
        AND pg_class.relname='t' --此处进行替换
ORDER BY  query_start;

 

6, see the PostgreSQL executing SQL

SELECT
    procpid,
    start,
    now() - start AS lap,
    current_query
FROM
    (SELECT
        backendid,
        pg_stat_get_backend_pid(S.backendid) AS procpid,
        pg_stat_get_backend_activity_start(S.backendid) AS start,
       pg_stat_get_backend_activity(S.backendid) AS current_query
    FROM
        (SELECT pg_stat_get_backend_idset() AS backendid) AS S
    ) AS S ,pg_stat_activity pa
WHERE
   current_query <> '<IDLE>' and  procpid<> pg_backend_pid() and pa.pid=s.procpid and pa.state<>'idle'
ORDER BY
   lap DESC; Start: process start time
 
procpid: Process the above mentioned id

lap: elapsed time
current_query: execution sql
how to stop executing sql
SELECT pg_cancel_backend (process id);
or use the system function
id kill -9 process;

 

- find out whether there is Waiting
PS -ef | grep Postgres | grep the wait

 

7, view the current database tables and indexes and sorts the size of the front display 20

SELECT
nspname,
relname,
relkind as "type",
pg_size_pretty(pg_table_size(C.oid)) AS size,
pg_size_pretty(pg_indexes_size(C.oid)) AS idxsize,
pg_size_pretty(pg_total_relation_size(C.oid)) as "total"
FROM pg_class C
LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
WHERE nspname NOT IN ('pg_catalog', 'information_schema') AND
nspname !~ '^pg_toast' AND
relkind IN ('r','i')
ORDER BY pg_total_relation_size(C.oid) DESC
LIMIT 20;


原文：https://blog.csdn.net/rudygao/article/details/49334001