On Thu, Feb 10, 2022 at 2:52 AM Julien Rouhaud <rjuju...@gmail.com> wrote: > Those extra WALs will also impact backups and replication. You could have > fancy hardware, a read-mostly workload and the need to replicate over a slow > WAN, and in that case the 10GB could be much more problematic.
True, I guess, but how bad does your WAN have to be for that to be an issue? On a 1 gigabit/second link, that's a little over 2 minutes of transfer time. That's not nothing, but it's not extreme, either, especially because there's no sense in querying an empty database. You're going to have to put some stuff in that database before you can do anything meaningful with it, and that's going to have to be replicated with or without this feature. I am not saying it couldn't be a problem, and that's why I'm endorsing making the behavior optional. But I think that it's a niche scenario. You need a bigger-than-normal template database, a slow WAN link, AND you need the amount of data loaded into the databases you create from the template to be small enough to make the cost of logging the template pages material. If you create a 10GB database from a template and then load 200GB of data into it, the WAL-logging overhead of creating the template is only 5%. I won't really be surprised if we hear that someone has a 10GB template database and likes to make a ton of copies and only change 500 rows in each one while replicating the whole thing over a slow WAN. That can definitely happen, and I'm sure whoever is doing that has reasons for it which they consider good and sufficient. However, I don't think there are likely to be a ton of people doing stuff like that - just a few. -- Robert Haas EDB: http://www.enterprisedb.com
