Re: Showing I/O timings spent reading/writing temp buffers in EXPLAIN

Em qui., 19 de ago. de 2021 às 09:21, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
escreveu:

> Hi all ,
>
> It's reported on pgsql-bugs[1] that I/O timings in EXPLAIN don't show
> the one for temp files. I think it's not a bug but could be an item
> for PG15. As mentioned on that thread, this would be useful for users
> in a case where temp buffers I/O used most of the time. So I've
> written the patch for that. Please note that the patch includes only
> to show temp buffer I/O timing to EXPLAIN but not other possibly
> related changes such as pg_stat_statement improvements yet.
>
> Before (w/o patch):
> postgres(1:14101)=# explain (analyze, buffers) select count(*) from
> generate_series(1,100000);
> QUERY PLAN
>
> -----------------------------------------------------------------------------------------------------------------------------------
> Aggregate (cost=1250.00..1250.01 rows=1 width=8) (actual
> time=59.025..59.026 rows=1 loops=1)
> Buffers: temp read=171 written=171
> -> Function Scan on generate_series (cost=0.00..1000.00
> rows=100000 width=0) (actual time=21.695..45.524 rows=100000 loops=1)
> Buffers: temp read=171 written=171
> Planning Time: 0.041 ms
> Execution Time: 70.867 ms
> (6 rows)
>
> After (w/ patch):
> postgres(1:28754)=# explain (analyze, buffers) select count(*) from
> generate_series(1,100000);
> QUERY PLAN
>
> -----------------------------------------------------------------------------------------------------------------------------------
> Aggregate (cost=1250.00..1250.01 rows=1 width=8) (actual
> time=56.189..56.190 rows=1 loops=1)
> Buffers: temp read=171 written=171
> I/O Timings: temp read=0.487 write=2.073
> -> Function Scan on generate_series (cost=0.00..1000.00
> rows=100000 width=0) (actual time=21.072..42.886 rows=100000 loops=1)
> Buffers: temp read=171 written=171
> I/O Timings: temp read=0.487 write=2.073
> Planning Time: 0.041 ms
> Execution Time: 59.928 ms
> (8 rows)
>
> Feedback is very welcome.
>
The presentation seems a little confusing, wouldn't it be better?

I/O Timings: shared/local read=xxxx write=xxx temp read=0.487 write=2.073

I think can remove this lines:
+ if (has_temp_timing)
+ appendStringInfoChar(es->str, ',');

regards,
Ranier Vilela