On Tue, Nov 16, 2010 at 5:46 PM, Josh Berkus <josh@xxxxxxxxxxxx> wrote: > Folks, > > Please help us resolve a discussion on -hackers. > > PostgreSQL 9.1 is likely to have, as a feature, the ability to create > tables which are "unlogged", meaning that they are not added to the > transaction log, and will be truncated (emptied) on database restart. > Such tables are intended for highly volatile, but not very valuable, > data, such as session statues, application logs, etc. > > The question is, how would you, as a DBA, expect pg_dump backups to > treat unlogged tables? Backing them up by default has the potential to > both cause performance drag on the unlogged table and make your backups > take longer unless you remember to omit them. Not backing them up by > default has the drawback that if you forget --include-unlogged switch, > and shut the database down, any unlogged data is gone. How would you > *expect* unlogged tables to behave? For 'as regular table' argument: We are *assuming* the data is not very valuable. I'd rather assume it is valuable. pg_dump has a very specific purpose: to back up the database in it's current state into a file that can replay that state. Not backing up large objects by default is a huge gotcha imnsho. I understand the reasoning, but disagree with it. Certainly a switch to tune them out would be nice, but not the default. Against argument: hm, I guess the counter agrument is that since because they are not WAL logged, they can't possibly be replayed to a standby, and it makes sense to have pg_dump and archive log based backup behave in similar fashion. It's weird that different backup strategies produce different results. I think the 'against argument' is stronger by about .5, so I'm voting .5 for pg_dump not to dump them. In fact, if that side of it wins, maybe pg_dump shouldn't even deal with them at all. I guess that would by my position. merlin -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
