On Fri, 1 Dec 2017 21:47:43 +0100 Tomas Vondra <tomas.von...@2ndquadrant.com> wrote: > > +1 to do the rewrite, just like for other similar ALTER TABLE commands
Ok. What about the following syntax: ALTER COLUMN DROP COMPRESSION - removes compression from the column with the rewrite and removes related compression options, so the user can drop compression method. ALTER COLUMN SET COMPRESSION NONE for the cases when the users want to just disable compression for future tuples. After that they can keep compressed tuples, or in the case when they have a large table they can decompress tuples partially using e.g. UPDATE, and then use ALTER COLUMN DROP COMPRESSION which will be much faster then. ALTER COLUMN SET COMPRESSION <cm> WITH <cmoptions> will change compression for new tuples but will not touch old ones. If the users want the recompression they can use DROP/SET COMPRESSION combination. I don't think that SET COMPRESSION with the rewrite of the whole table will be useful enough on any somewhat big tables and same time big tables is where the user needs compression the most. I understand that ALTER with the rewrite sounds logical and much easier to implement (and it doesn't require Oids in tuples), but it could be unusable. -- ---- Regards, Ildus Kurbangaliev
