The default log_line_prefix is empty, which is not what you want. A good starting value here is the following:
log_line_prefix='%t:%r:%u@%d:[%p]: '
This will put the following into every log line:
- %t: Timestamp
- %u: Database user name
- %r: Remote host connection is from
- %d: Database connection is to
- %p: Process ID of connection
It may not be obvious what you'd want all of these values for initially, particularly the process ID. Once you've tried to chase down a few performance issues, the need for saving these values will be more obvious, and you'll be glad to already have this data logged.
Another approach worth considering is setting log_line_prefix such that the resulting logs will be compatible with the pgFouine program, ...
