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

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.

Regards,

[1] https://www.postgresql.org/message-id/20210709084355.GA6251%40depesz.com

--
Masahiko Sawada
EDB: https://www.enterprisedb.com/