Re: Why does logical replication launcher set application_name?

On Wed, Apr 12, 2017 at 6:02 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Tue, Apr 11, 2017 at 8:11 PM, Michael Paquier
> <michael(dot)paquier(at)gmail(dot)com> wrote:
>> On Wed, Apr 12, 2017 at 3:40 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> I notice looking at pg_stat_activity that the logical replication launcher
>>> sets its application_name to "logical replication launcher". This seems
>>> inconsistent (no other standard background process sets application_name),
>>> redundant with other columns that already tell you what it is, and an
>>> unreasonable consumption of horizontal space in the tabular output.
>>> Can we drop that? If we do have to have something like that, what about
>>> putting it in the "query" field where it's much less likely to be
>>> substantially wider than any other entry in the column?
>>
>> It seems to me that the logic behind that is to be able to identify
>> easily the logical replication launcher in pg_stat_activity, so using
>> the query field instead sounds fine for me as we need another way than
>> backend_type to guess what is this bgworker.
>
> Wait, why do we need two ways?
>
For backend_type=background worker, application_name shows the name of
the background worker (BackgroundWorker->bgw_name). I think we need
some way to distinguish among different background workers. But,
application_name may not be the correct field to show the information.

--
Thanks & Regards,
Kuntal Ghosh
EnterpriseDB: http://www.enterprisedb.com