Help Center/ GaussDB/ Developer Guide(Centralized_2.x)/ Performance Tuning/ Determining the Scope of Performance Tuning/ Checking Blocked Statements
Updated on 2023-10-23 GMT+08:00
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Checking Blocked Statements

During database running, query statements are blocked in some service scenarios and run for an excessively long time. In this case, you can forcibly terminate the faulty session.

Procedure

  1. Connect to a database. For details, see Connecting to a Database.
  2. View blocked query statements and details about the tables and schemas that block the query statements. 

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    SELECT w.query as waiting_query,
w.pid as w_pid,
w.usename as w_user,
l.query as locking_query,
l.pid as l_pid,
l.usename as l_user,
t.schemaname || '.' || t.relname as tablename
from pg_stat_activity w join pg_locks l1 on w.pid = l1.pid
and not l1.granted join pg_locks l2 on l1.relation = l2.relation
and l2.granted join pg_stat_activity l on l2.pid = l.pid join pg_stat_user_tables t on l1.relation = t.relid
where w.waiting;

    The thread ID, user details, query status, as well as details about the tables and schemas that block the query statements are returned.

  3. Run the following command to terminate the required session, where 139834762094352 is the thread ID: 

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    SELECT PG_TERMINATE_BACKEND(139834762094352);

    If information similar to the following is displayed, the session is successfully terminated:

     PG_TERMINATE_BACKEND
----------------------
 t
(1 row)

    If information similar to the following is displayed, a user is attempting to terminate the session, and the session will be reconnected rather than being terminated.

    FATAL:  terminating connection due to administrator command
FATAL:  terminating connection due to administrator command
The connection to the server was lost. Attempting reset: Succeeded.

    If the PG_TERMINATE_BACKEND function is used to terminate the background threads of the session, the gsql client will be reconnected rather than be logged out.