On Wed, Dec 29, 2010 at 11:16:23AM -0500, Tom Lane wrote: > Noah Misch <n...@leadboat.com> writes: > > ALTER TABLE ALTER TYPE always rewrites the table heap and its indexes. In > > some > > cases, we can determine that doing so is unhelpful, and that the conversion > > shall always succeed: > > I wish to replace table rewrites with table verification scans where > > possible, > > then skip those verification scans where possible. > > This has been discussed before; have you read the previous threads?
I cited two threads I had read on the subject. Were there other important ones? > I really really dislike the notion of a "verification scan": it's > basically work that is going to be useless if it fails. I think your > argument that it will usually fail quickly is quite unconvincing, and in > any case the situations where it is useful at all are too thin on the > ground to be worth the code space to implement it. It seems sufficient > to me to skip the rewrite in cases of provable binary compatibility, with > possibly an extra check for "safe" changes of typmod. With respect to > the latter, I agree a type-specific function to compare the typmods > would be the way to go, although "exemptor" seems a pretty badly chosen > name for it. I have attempted to expand on these problems in my reply to Robert. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
