Checking which queries are active or blocked

Here, we will show you how to know whether a query is actually running or waiting for another query.

Getting ready

If you are logged in as superuser you will have full access to monitoring information.

How to do it...

On PostgreSQL 9.6 or newer you can run the following query:

SELECT datname
, usename
, wait_event_type
, wait_event
, query
FROM pg_stat_activity
WHERE wait_event IS NOT NULL;

The output will look like the following:

-[ RECORD 1 ]---+-----------------
datname         | postgres
usename         | gianni
wait_event_type | Lock
wait_event      | relation
query           | select * from t;

If your PostgreSQL installation is older than 9.6, you should run this query instead:

SELECT datname, usename, query
FROM pg_stat_activity
WHERE waiting = true;

You will get a list of queries that are waiting on other backends

How it works...

In 9.6 or newer, the pg_stat_activity system view includes the wait_event_type and wait_event columns, which are set respectively...