Everything goes well until just now, I am pretty sure I haven't modified any configuration about cert or SSL, but when I execute $koji moshimoshi, it shows :

"2023-03-16 15:46:38,806 [ERROR] koji: Fault: : column "closed" does not exist\nLINE 5: WHERE (closed IS FALSE)\n ^\n'>"

/var/lib/pgsql/data/log/postgresql-Thu.log:

2023-03-16 11:38:15.964 CST [1545579] LOG: listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
2023-03-16 11:38:15.964 CST [1545579] LOG: listening on Unix socket "/tmp/.s.PGSQL.5432"
2023-03-16 11:38:15.966 CST [1545581] LOG: database system was shut down at 2023-03-16 11:38:15 CST
2023-03-16 11:38:15.971 CST [1545579] LOG: database system is ready to accept connections
2023-03-16 11:38:19.784 CST [1545992] ERROR: column "closed" does not exist at character 179
2023-03-16 11:38:19.784 CST [1545992] STATEMENT:
SELECT authtype, callnum, exclusive, expired, master, start_time, date_part('epoch', start_time), update_time, date_part('epoch', update_time), user_id
FROM sessions

WHERE (closed IS FALSE)
AND (hostip = '10.4.8.140')
AND (id = 2862)
AND (key = '2-CIuA7Y3IjEDL4zVef54')

FOR UPDATE
2023-03-16 11:38:25.807 CST [1546301] ERROR: column "closed" does not exist at character 179
2023-03-16 11:38:25.807 CST [1546301] STATEMENT:
SELECT authtype, callnum, exclusive, expired, master, start_time, date_part('epoch', start_time), update_time, date_part('epoch', update_time), user_id
FROM sessions

WHERE (closed IS FALSE)
AND (hostip = '192.168.122.90')
AND (id = 564)
AND (key = '3-mmzhc0qtNraAY8LXMy7')

/var/log/kojira.log:

2023-03-16 14:17:51,022 [ERROR] koji.repo: unable to obtain a session (ssl auth failed: requests.exceptions.ConnectionError: HTTPSConnectionPool(host='sh-koji.ambarella.com', port=443): Max retries exceeded with url: /kojihub/ssllogin (Caused by NewConnectionError(': Failed to establish a new connection: [Errno 111] Connection refused'))
)

/var/log/httpd/ssl_error_log:

[Thu Mar 16 11:38:19.785373 2023] [wsgi:error] [pid 1545794:tid 1545911] [client 10.4.8.140:60802] 2023-03-16 11:38:19,784 [ERROR] m=exclusiveSession u=None p=1545794 r=10.4.8.140:60802 koji.db: Query failed. Query was: b"\nSELECT authtype, callnum, exclusive, expired, master, start_time, date_part('epoch', start_time), update_time, date_part('epoch', update_time), user_id\n FROM sessions\n\n WHERE (closed IS FALSE)\n AND (hostip = '10.4.8.140')\n AND (id = 2862)\n AND (key = '2-CIuA7Y3IjEDL4zVef54')\n \n \n\n \n\n FOR UPDATE"
[Thu Mar 16 11:38:19.786467 2023] [wsgi:error] [pid 1545794:tid 1545911] [client 10.4.8.140:60802] 2023-03-16 11:38:19,786 [WARNING] m=exclusiveSession u=None p=1545794 r=10.4.8.140:60802 koji.xmlrpc: Traceback (most recent call last):

what should I do to debug the problem, what on earth happened to the PostgreSQL or kojira?

It looks that you don't have updated PostgreSQL scheme:
https://pagure.io/koji/blob/master/f/docs/schema-upgrade-1.31-1.32.sql#_10

It looks that you don't have updated PostgreSQL scheme:
https://pagure.io/koji/blob/master/f/docs/schema-upgrade-1.31-1.32.sql#_10

Thank you for your prompt reply and helpful suggestion.

To make sure, do you mean to append those lines to '/usr/share/doc/koji/docs/schema-upgrade-1.31-1.32.sql' manually?

Whenever you update koji hub, you need to consult corresponding page in https://docs.pagure.org/koji/migrations/migrations/

So, in this case

$ psql koji koji < /usr/share/doc/koji/docs/schema-upgrade-1.31-1.32.sql

Whenever you update koji hub, you need to consult corresponding page in https://docs.pagure.org/koji/migrations/migrations/

So, in this case
$ psql koji koji < /usr/share/doc/koji/docs/schema-upgrade-1.31-1.32.sql

Problem solved!
I will consult this page whenever I update koji hub.
Thank you Tomas!

This issue has been migrated to Fedora Forge:
https://forge.fedoraproject.org/koji/koji/issues/3737

Please continue any further discussion there.