On Tue, 2011-01-11 at 07:14 -0500, Noah Misch wrote: > These changes do make it harder to guess how much work the ALTER TABLE > will do. Indeed, about 1/4 of my own guesses prior to writing were > wrong. Something like WITHOUT REWRITE might be the way to go, though > there are more questions: if it does not rewrite, does it scan the > table? Which indexes, if any, does it rebuild? Which foreign key > constraints, if any, does it recheck? With patch 0, you can answer > all these questions by enabling DEBUG1 messages and trying the command > on your test system. For this reason, I did consider adding a VERBOSE > clause to show those messages at DETAIL, rather than unconditionally > showing them at DEBUG1. In any case, if a WITHOUT REWRITE like you > describe covers the important question, it's certainly easy enough to > implement.
Trouble is, only superusers can set DEBUG1. You're right, its more complex than I made out, though that strengthens the feeling that we need a way to check what it does before it does it, or a way to limit your expectations. Ideally that would be a programmatic way, so that pgAdmin et al can issue a warning. Given your thoughts above, my preference would be for EXPLAIN ALTER TABLE to describe the actions that will take place. Or other ideas... -- Simon Riggs http://www.2ndQuadrant.com/books/ PostgreSQL Development, 24x7 Support, Training and Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
