Re: Feature improvement: can we add queryId for pg_catalog.pg_stat_activity view?

On Wed, Aug 19, 2020 at 04:19:30PM +0200, Julien Rouhaud wrote:
> Similarly to other fields in pg_stat_activity, only the queryid from the top
> level statements are exposed, and if the backends status isn't active then the
> queryid from the last executed statements is displayed.
>
> Also add a %Q placeholder to include the queryid in the log_line_prefix, which
> will also only expose top level statements.

I would like to apply this patch (I know it has been in the commitfest
since July 2019), but I have some questions about the user API. Does it
make sense to have a column in pg_stat_actvity and an option in
log_line_prefix that will be empty unless pg_stat_statements is
installed? Is there no clean way to move the query hash computation out
of pg_stat_statements and into the main code so the query id is always
visible? (Also, did we decide _not_ to make the pg_stat_statements
queryid always a positive value?)

Also, in the doc patch:

By default, query identifiers are not computed, so this field will always
be null, unless an additional module that compute query identifiers, such
as <xref linkend="pgstatstatements"/>, is configured.

why are you saying "such as"? Isn't pg_stat_statements the only way to
see the queryid? This command allowed the queryid to be displayed in
pg_stat_activity:

ALTER SYSTEM SET shared_preload_libraries = 'pg_stat_statements';

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Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EnterpriseDB https://enterprisedb.com

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