%d in log_line_prefix doesn't work for bg/autovacuum workers

Hi,

elog.c's log_line_prefix() processes %d with:
case 'd':
if (MyProcPort)
{
const char *dbname = MyProcPort->database_name;

if (dbname == NULL || *dbname == '\0')
dbname = _("[unknown]");
if (padding != 0)
appendStringInfo(buf, "%*s", padding, dbname);
else
appendStringInfoString(buf, dbname);
}
else if (padding != 0)
appendStringInfoSpaces(buf,
padding > 0 ? padding : -padding);
write_csvlog() uses similar logic.

Unfortunately MyProcPort only exists in user initiated backends.

It's imo pretty annoying that neither bgworkers nor autovacuum workers
show the proper database in the log. Why don't we just populate a global
variable in InitPostgres() once we're sure which database the backend is
connected to? We could fill fake MyProcPorts, but that doesn't seem like
a good idea to me.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services