Re: Rethinking plpgsql's assignment implementation

Pavel Stehule <pavel.stehule@gmail.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