The short answer is don't do that if the table is pretty big unless you can afford prolonged outage. The better way is to add new column, add triggers to populate it on insert/update/delete, backfill, and swap
Pg 9.6.24 (Yes, I know; it's out of my control.)
I'm ALTERing that table to change a column from INTEGER to BIGINT. Of
course, all of the partitions are pretty big.
Even though it's one giant transaction, is there any way for me to monitor
it's progress?
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Born in Arizona, moved to Babylonia.