Re: In PG12, query with float calculations is slower than PG11

Thank you very much everyone.

Improvement was confirmed even if PG12_STABLE was built with gcc 4.8.5.

* PG_12_STABLE
* gcc 4.8.5

postgres=# EXPLAIN (ANALYZE on, VERBOSE on, BUFFERS on)
select (2 * a) , (2 * b) , (2 * c), (2 * d), (2 * e)
from realtest;

QUERY PLAN

------------------------------------------------------------------------------------------------------------------------
Seq Scan on public.realtest (cost=0.00..288692.14 rows=9999873 width=40)
(actual time=0.012..4118.432 rows=10000001 loops=1)
Output: ('2'::double precision * a), ('2'::double precision * b),
('2'::double precision * c), ('2'::double precision * d), ('2'::double
precision * e)
Buffers: shared hit=63695
Planning Time: 0.034 ms
Execution Time: 4811.957 ms
(5 rows)

32.03% postgres postgres [.] ExecInterpExpr
12.28% postgres postgres [.] float84mul
9.62% postgres [vdso] [.] __vdso_clock_gettime
6.45% postgres libc-2.17.so [.] __isinf
5.15% postgres postgres [.] tts_buffer_heap_getsomeattrs
3.83% postgres postgres [.] ExecScan

Best Regards,
Keisuke Kuroda

2020年2月14日(金) 13:29 Amit Langote <amitlangote09(at)gmail(dot)com>:

> On Fri, Feb 14, 2020 at 3:47 AM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > On 2020-02-13 13:40:43 -0500, Tom Lane wrote:
> > > ... and pushed. One other change I made beyond those suggested
> > > was to push the zero-divide ereport's out-of-line as well.
> >
> > Thanks!
>
> Thank you all.
>
> I repeated some of the tests I did earlier and things look good.
>
> gcc-8
> =====
>
> HEAD
>
> latency average = 296.842 ms
>
> 42.05% postgres postgres [.] ExecInterpExpr
> 15.14% postgres postgres [.] float8_accum
> 9.32% postgres libc-2.17.so [.] __isinf
> 7.32% postgres postgres [.] dsqrt
> 5.67% postgres postgres [.] float8mul
> 4.20% postgres postgres [.] ftod
>
> 11.7
>
> latency average = 289.439 ms
>
> 41.52% postgres postgres [.] ExecInterpExpr
> 13.59% postgres libc-2.17.so [.] __isinf
> 10.98% postgres postgres [.] float8_accum
> 8.26% postgres postgres [.] dsqrt
> 6.17% postgres postgres [.] float8mul
> 3.65% postgres postgres [.] ftod
>
> clang-7
> =======
>
> HEAD
>
> latency average = 233.735 ms
>
> 43.84% postgres postgres [.] ExecInterpExpr
> 15.17% postgres postgres [.] float8_accum
> 8.25% postgres postgres [.] dsqrt
> 7.35% postgres postgres [.] float8mul
> 5.84% postgres postgres [.] ftod
> 3.78% postgres postgres [.] tts_buffer_heap_getsomeattrs
>
> 11.7
>
> latency average = 221.009 ms
>
> 49.55% postgres postgres [.] ExecInterpExpr
> 12.05% postgres postgres [.] float8_accum
> 8.97% postgres postgres [.] dsqrt
> 6.72% postgres postgres [.] float8mul
> 5.62% postgres postgres [.] ftod
> 2.18% postgres postgres [.] slot_deform_tuple
>
> HEAD and PG 11 are now comparable even when built with gcc.
>
> Regards,
> Amit
>