Hello, Sergey! 09.01.2018, 15:53, "Sergei Kornilov" <s...@zsrv.org>: > 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/81911511895...@web58j.yandex.ru#81911511895...@web58j.yandex.ru > > Regards, Sergei -- Timokhin 'maf' Maxim
