Postgres stuck with ALTER query onp roduction

Question

So I have this big database in production having partitions on date field. I ran this migration to add a new column and its now 1-hour db is stuck not responding and still migrating.

ALTER TABLE public.ur_sms_traffic ADD COLUMN trace_id varchar(16);

The table has no relation. just stand-alone table,

Answer 1

I found the issue by checking pg_stat_activity: someone ran a very big query in production and it was holding the migration.