From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
Cc: | Chapman Flack <chap(at)anastigmatix(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Rethinking plpgsql's assignment implementation |
Date: | 2020-12-14 16:25:16 |
Message-ID: | 911973.1607963116@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
> I checked a performance and it looks so access to record's field is faster,
> but an access to arrays field is significantly slower
Hmm, I'd drawn the opposite conclusion in my own testing ...
> for i in 1..5000
> loop
> if a[i] > a[i+1] then
> aux := a[i];
> a[i] := a[i+1]; a[i+1] := aux;
> rep := true;
> end if;
> end loop;
... but I now see that I'd not checked cases like "a[i] := a[j]".
exec_check_rw_parameter() is being too conservative about whether
it can optimize a case like that. The attached incremental patch
fixes it.
> I tested pi calculation
> ...
> And the performance is 10% slower than on master
Can't reproduce that here. For the record, I get the following
timings (medians of three runs) for your test cases:
HEAD:
sort: Time: 13974.709 ms (00:13.975)
pi_est_1(10000000): Time: 3537.482 ms (00:03.537)
pi_est_2(10000000): Time: 3546.557 ms (00:03.547)
Patch v1:
sort: Time: 47053.892 ms (00:47.054)
pi_est_1(10000000): Time: 3456.078 ms (00:03.456)
pi_est_2(10000000): Time: 3451.347 ms (00:03.451)
+ exec_check_rw_parameter fix:
sort: Time: 12199.724 ms (00:12.200)
pi_est_1(10000000): Time: 3357.955 ms (00:03.358)
pi_est_2(10000000): Time: 3367.526 ms (00:03.368)
I'm inclined to think that the differences in the pi calculation
timings are mostly chance effects; there's certainly no reason
why exec_check_rw_parameter should affect that test case at all.
regards, tom lane
Attachment | Content-Type | Size |
---|---|---|
v1-0007-performance-fix.patch | text/x-diff | 1.5 KB |
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