`log_line_prefix = '%m (%p:%h:%d:%u:%a:%v:%x) '`

`2019-08-16 05:08:57.939 GMT (62842:host:database:user:[application]:16/36976788:3643551317) LOG: process 62842 still waiting for ExclusiveLock on tuple (113892,1) of relation 14028231 of database 12345 after 1000.098 ms`

```
%p = 62842
%v = 16/36976788
%x = 3643551317

# special values:
#   %p = process ID
#   %v = virtual transaction ID
#   %x = transaction ID (0 if none)
```