Re: Planning counters in pg_stat_statements (using pgss_store)

On Thu, May 21, 2020 at 08:49:53AM +0200, Julien Rouhaud wrote:
> On Tue, May 19, 2020 at 4:29 AM Andy Fan <zhihui.fan1213@gmail.com> wrote:
>> Thanks for the excellent extension. I want to add 5 more fields to satisfy the
>> following requirements.
>>
>> int   subplan; /* No. of subplan in this query */
>> int   subquery; /* No. of subquery */
>> int   joincnt; /* How many relations are joined */
>> bool hasagg; /* if we have agg function in this query */
>> bool hasgroup; /* has group clause */
>
> Most of those fields can be computed using the raw sql satements.  Why
> not adding functions like query_has_agg(querytext) to get the
> information from pgss stored query text instead?

Yeah I personally find concepts related only to the query string
itself not something that needs to be tied to pg_stat_statements.
While reading about those five new fields, I am also wondering how
this stuff would work with CTEs.  Particularly, should the hasagg or
hasgroup flags be set only if the most outer query satisfies a
condition?  What if an inner query satisfies a condition but not an
outer query?  Should joincnt just be the sum of all the joins done in
all queries, including subqueries?
--
Michael