Hello

> 1. ALTER TABLE clusters ADD COLUMN "is_paid" BOOLEAN DEFAULT FALSE;
this is wrong. To avoid large table lock you need DEFAULT NULL:
ALTER TABLE clusters ADD COLUMN "is_paid" BOOLEAN DEFAULT NULL;
Default null changes only system catalog, default with any non-null value will 
rewrite all rows. After adding column you can set default value - it applied 
only for future inserts:
ALTER TABLE clusters ALTER COLUMN "is_paid" SET DEFAULT FALSE;

And then you can update all old rows in table by small chunks. Finally, when 
here is no NULL values you can set not null:
ALTER TABLE clusters ALTER COLUMN "is_paid" SET NOT NULL;
But unfortunately this locks table for some time - smaller what rewrite time, 
but time of full seqscan. I hope my patch [1] will be merged and not null can 
be set in future by temporary adding check constraint (not valid, then 
validate) - which not require large table lock

[1] 
https://www.postgresql.org/message-id/flat/81911511895...@web58j.yandex.ru#81911511895...@web58j.yandex.ru

Regards, Sergei

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