Re: [HACKERS] Reporting planning time with EXPLAIN

On Tue, Dec 27, 2016 at 1:27 PM, Ashutosh Bapat
<ashutosh.bapat@enterprisedb.com> wrote:
> Hi,
> We report planning and execution time when EXPLAIN ANALYZE is issued.
> We do not have facility to report planning time as part EXPLAIN
> output. In order to get the planning time, one has to issue EXPLAIN
> ANALYZE which involves executing the plan, which is unnecessary.
>

+1.  I think getting to know planning time is useful for cases when we
are making changes in planner to know if the changes has introduced
any regression.

>
> One can use this option as
> postgres=# explain (summary on) select * from pg_class c, pg_type t
> where c.reltype = t.oid;
>                                 QUERY PLAN
> --------------------------------------------------------------------------
>  Hash Join  (cost=17.12..35.70 rows=319 width=511)
>    Hash Cond: (c.reltype = t.oid)
>    ->  Seq Scan on pg_class c  (cost=0.00..14.19 rows=319 width=259)
>    ->  Hash  (cost=12.61..12.61 rows=361 width=256)
>          ->  Seq Scan on pg_type t  (cost=0.00..12.61 rows=361 width=256)
>  Planning time: 48.823 ms
> (6 rows)
>
> When analyze is specified, summary is also set to ON. By default this
> flag is OFF.
>

I am not sure whether using *summary* to print just planning time is a
good idea.  Another option could be SUMMARY_PLAN_TIME.

+ /* Execution time matters only when analyze is requested */
+ if (es->summary && es->analyze)

Do you really need es->summary in above check?

We should update documentation of Explain command, but maybe that can
wait till we finalize the specs.

-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com