Display individual query in pg_stat_activity

Hi hackers,

I've attached a patch to display individual query in the pg_stat_activity query field when multiple SQL statements are currently displayed.

Motivation:

When multiple statements are displayed then we don’t know which one is currently running.

For example:

psql -c "select pg_sleep(10);select pg_sleep(20);" is currently displayed as:

postgres=# select backend_type,query from pg_stat_activity;         backend_type         |                      query
------------------------------+-------------------------------------------------- client backend               | select pg_sleep(10);select pg_sleep(20);

Showing which statement is currently being executed would be more helpful.

Technical context and proposal:

There is 2 points in this patch:

• modifying the current behavior in “exec_simple_query”
• modifying the current behavior in “ExecInitParallelPlan”

So that we could see for example:

         backend_type         |                      query
------------------------------+-------------------------------------------------- client backend               | select pg_sleep(10);

and then

         backend_type         |                      query
------------------------------+-------------------------------------------------- client backend               | select pg_sleep(20);

instead of the multiple sql statement described in the “motivation” section.

Another example: parallel worker being triggered while executing a function:

create or replace function test()
returns void as $$select count() as "first" from foo;select pg_sleep(10);select count() as "second" from foo;select pg_sleep(11);select pg_sleep(10)
$$
language sql;

We currently see:

         backend_type         |                                                                query
------------------------------+-------------------------------------------------------------------------------------------------------------------------------------- client backend               | select test(); parallel worker              | select count(*) as "first" from foo;select pg_sleep(10);select count(*) as "second" from foo;select pg_sleep(11);select pg_sleep(10)+                              | parallel worker              | select count(*) as "first" from foo;select pg_sleep(10);select count(*) as "second" from foo;select pg_sleep(11);select pg_sleep(10)+                              |

while the attached patch would provide:

          backend_type         |                      query                                                                                                                                                                                                                                                  [217/1938]
------------------------------+-------------------------------------------------- client backend               | select test(); parallel worker              | select count(*) as "first" from foo; parallel worker              | select count(*) as "first" from foo;

and then:

         backend_type         |                      query
------------------------------+-------------------------------------------------- client backend               | select test(); parallel worker              | select count(*) as "second" from foo; parallel worker              | select count(*) as "second" from foo;

I will add this patch to the next commitfest. I look forward to your feedback about the idea and/or implementation.

Regards,
Bertrand