Quick connection string/connectivity test using DBLINK

Ever had that sinking feeling when you’re setting up logical replication and CREATE SUBSCRIPTION... just kinda sat there? Maybe it eventually timed out?

I used to use foreign data wrappers to troubleshoot database-to-database connectivity problems, but using DBLINK is much easier. (Bonus: can be used to troubleshoot connectivity problems with foreign data wrappers, also!) Hat tip to Xof for sharing it.

-- Create the DBLINK extension in both databases
CREATE EXTENSION dblink;

-- From either side:
SELECT * FROM dblink (
'',
'SELECT 1'
) AS test(i int);

Example successful output:

gabrielle=# SELECT * FROM dblink (
    'port=5433 dbname=gabrielle',
    'SELECT 1'
  ) AS test(i int);

 i 
---
 1
(1 row)