On Wed, Nov 3, 2021 at 9:04 AM Bruce Momjian <br...@momjian.us> wrote: > Well, another issue is that if something unusual does happen, it appears > very visibly if you are looking just for LOG messages, while if you have > many checkpoint log messages, it might get lost.
That's a theoretical risk, but in practice the problem is actually exactly the opposite of that, at least in my experience. If somebody sends me a log file from a machine with log_checkpoints=on, the file is typically hundreds of megabytes in size and in that file someplace there are a handful of log lines generated by log_checkpoints mixed in with millions of log lines about other things. So it's not that log_checkpoints=on would keep you from noticing other things happening on the machine. It's that other things happening on the machine would keep you from noticing the log_checkpoints=on output. In fact this problem is true for pretty much anything important that shows up in the log: it's likely to be completely swamped by other messages logged *at the exact same log level* that are not important at all. The ERROR that could have alerted you to data corruption is likely mixed in with millions of innocuous ERROR messages, for example. > If we want to log more > by default, I think we are looking at several issues: > > * enabling log rotation and log file reuse in the default install > * changing the labels of some of the normal-operation log messages > * changing the way some of these log messages are controlled > * perhaps using a ring buffer for common log messages If we were talking about increasing the log volume by an amount that was actually meaningful, we might need to think about these things, but that's not what is being proposed. The only systems where this is going to lead to a significant percentage increase in log volume are the ones that are pretty much idle now. On real systems, this is going to lead to a change that is less than 1%, and maybe less than 0.001%. We don't have to rearchitect anything as a result of decisions that have so little practical impact - especially considering that at least some packagers are already putting log rotation in place automatically, in a way consistent with distro policies. -- Robert Haas EDB: http://www.enterprisedb.com