Re: backend type in log_line_prefix?

On Fri, Mar 13, 2020 at 10:22:52PM +0100, Peter Eisentraut wrote:
> >Can I suggest:
> >
> >-               appendCSVLiteral(&buf, MyBgworkerEntry->bgw_type);
> >+               appendCSVLiteral(&buf, MyBgworkerEntry->bgw_name);
> 
> The difference is intentional.  bgw_type is so that you can filter and group
> by type.  The bgw_name could be totally different for each instance.

I found 5373bc2a0867048bb78f93aede54ac1309b5e227

Your patch adds bgw_type, which is also in pg_stat_activity, so I agree it's
good to allow include it log_line_prefix and CSV.

I suggest the CSV/log should also have the leader_pid, corresponding to
| b025f32e0b Add leader_pid to pg_stat_activity

With the attached on top of your patch, CSV logs like:

2020-03-14 22:09:39.395 CDT,"pryzbyj","template1",17030,"[local]",5e6d9c69.4286,2,"idle",2020-03-14 22:09:29
CDT,3/23,0,LOG,00000,"statement:explain analyze SELECT COUNT(1), a.a FROM t a JOIN t b ON a.a=b.a GROUP BY
2;",,,,,,,,,"psql","clientbackend",
 
2020-03-14 22:09:43.094 CDT,,,17042,,5e6d9c73.4292,1,,2020-03-14 22:09:39 CDT,4/3,0,LOG,00000,"temporary file: path
""base/pgsql_tmp/pgsql_tmp17042.0"",size 4694016",,,,,,"explain analyze SELECT COUNT(1), a.a FROM t a JOIN t b ON
a.a=b.aGROUP BY 2;",,,"psql","parallel worker",17030
 
2020-03-14 22:09:43.094 CDT,,,17043,,5e6d9c73.4293,1,,2020-03-14 22:09:39 CDT,5/3,0,LOG,00000,"temporary file: path
""base/pgsql_tmp/pgsql_tmp17043.0"",size 4694016",,,,,,"explain analyze SELECT COUNT(1), a.a FROM t a JOIN t b ON
a.a=b.aGROUP BY 2;",,,"psql","parallel worker",17030
 

As for my question "what's using/trying/failing to use parallel workers", I was
able to look into that by parsing "Workers Planned/Launched" from autoexplain.
It's not a *good* way to do it, but I don't see how to do better and I don't
see any way this patch can improve that.

-- 
Justin