Atler Table Alter Column Set Default FALSE: Why my alter table took 10 minutes to finish? I have run the following command and it took about 10 minutes to finish:

ALTER TABLE "bookings" ALTER COLUMN "local_direct_booking" SET DEFAULT FALSE


for a table bookings which had 111.834 rows (about 111K rows).

I don't believe this is a big table. 

This is the size of the table:

lvd-am::DATABASE=&gt; SELECT pg_size_pretty( pg_total_relation_size('bookings') );
 pg_size_pretty 
----------------
 213 MB
(1 row)


Do you have any hint why this might have taken that long?
There must have been a concurrent long running transaction that used (perhaps read from) the table. Check pg_stat_activity for sessions with a state other than idle.