On Tue, Nov 2, 2021 at 8:02 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > I'm still of the position that the default ought to be that a > normally-functioning server generates no ongoing log output. > Only people who have got Nagios watching their logs, or some > such setup, are going to want anything different. And that is > a minority use-case. There are going to be way more people > bitching because their postmaster log overflowed their disk > than there will be people who are happier because you made > such output the default. (Don't forget that our default > logging setup does not rotate the logs.)
I mean, you still seem to be postulating a setup where none of the user activity ever causes any logging messages to get generated, which is just not the way real systems behave. And as to log volume, if you log a checkpoint every 5 minutes, generating roughly 1/4 kB of log output each time, that's ~3kB/hour, or ~27MB/year. Just for fun, I went and had a look at the least-used PostgreSQL instances that I know about, which is the one running on my Raspberry Pi. It powers a little web site that I wrote and people sometimes use that web site but not that often. It's running PostgreSQL 9.4.5 because it's not an important enough system that I can be bothered to upgrade it. The OS that came preinstalled is some Debian derivative that arranges to rotate the logs automatically, so I only have logs going back to May. For the most part, it generates pretty much nothing in the logs, although back end of May/early June it kicked out about 56MB of logs. I guess I must have temporarily enabled log_statement=all to debug something or other. Anyway, there are three points I'd like to make about this machine. The first is that the root partition, where pretty much all the files are located on this tiny box, is 6GB. It currently has 825MB of free space. If you enabled log_checkpoints=on on this machine, first of all I suppose most of the time it wouldn't log anything because there's usually no activity and thus the checkpoint could just be skipped. Second, even if it did checkpoint every 5 minutes and generate 27MB/year of logs, that would take roughly 30 years to free up the 825MB of free space I have on the root partition. I doubt this machine will be around in 30 years; it's uncertain that *I'll* be around in 30 years. Third, this machine came with PostgreSQL log compression and rotation set up by the operating system, which I think is pretty good evidence that configurations including those features are common. The compression ratio on the logs this machine is generating seems to be about 98.5%. After compression, the overhead of the log_checkpoints output for the three months of logs that it keeps - assuming it had enough activity to checkpoint every 5 minutes - would be perhaps 100kB, which is not only little enough not to be a problem on this machine, but also little enough not to be a problem on the first IBM PC that I ever used, back in the 1980s. If log_checkpoints=on wouldn't fill up the disk on my 5+-year old Raspberry Pi in less time that it takes to raise multiple children to adulthood even after disabling the OS-provided log rotation and compression, then it seems more than fair to say that for the vast majority of users, this isn't a real problem. And for those few for whom it *is* a real problem, they can still shut off log_checkpoints. It's not like anybody is proposing to remove the option. -- Robert Haas EDB: http://www.enterprisedb.com
