Hello, Sergey! 09.01.2018, 15:53, "Sergei Kornilov" <sk@xxxxxxxx>: > 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: What you wrote are exactly I'm doing. Moreover, I'm checking current metrics to avoid previously problems. > 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 Hope your commit will be merged. It will be realy useful. > > [1] https://www.postgresql.org/message-id/flat/81911511895540@xxxxxxxxxxxxxxxx#81911511895540@xxxxxxxxxxxxxxxx > > Regards, Sergei -- Timokhin 'maf' Maxim
