Ühel kenal päeval, N, 2006-06-08 kell 11:42, kirjutas Greg Stark: > Hannu Krosing <[EMAIL PROTECTED]> writes: > > > Do you mean that in newer versions ALTER TABLE ADD COLUMN will change > > existing data without asking me ? > > > > That would be evil! > > > > Even worse if ALTER TABLE ALTER COLUMN SET DEFAULT would do the same. > > postgres=# alter table test add b integer default 1; > ALTER TABLE > postgres=# select * from test; > a | b > ---+--- > 0 | 1 > (1 row) > > > > It was awfully annoying for users when that feature was missing. > > > Any non-linearities in the user interface like this > > > end up being surprises and annoyances for users. > > > > I would be *really*, *really*, *really* annoyed if an op that I expected > > to take less than 1 sec takes 5 hours and then forces me to spend > > another 10 hours on VACUUM FULL+REINDEX or CLUSTER to get performance > > back. > > I forget whether the developer managed to get it working without doing any > table rewriting. In theory the table just needs to know that records that are > "missing" that column in the null bitmap should behave as if they have the > default value. But I seem to recall some headaches with that approach.
I remember that discussion, but I'm surprised that something got implemented and accepted into core with so many unsolvable problems/logical inconsistencies/new pitfalls. for example - to be consistent, one should also make "ALTER TABLE ALTER COLUMN col SET DEFAULT x" change each "default" value, no ? but how should one know it for records which are updated, possibly in columns newer than the one with changed DEFAULT. Or was a new default bitmap introduced in addition to null bitmap ? -- ---------------- Hannu Krosing Database Architect Skype Technologies OÜ Akadeemia tee 21 F, Tallinn, 12618, Estonia Skype me: callto:hkrosing Get Skype for free: http://www.skype.com ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
