| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
| Cc: | Beena Emerson <memissemerson(at)gmail(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Robert Haas <robertmhaas(at)gmail(dot)com>, amul sul <sulamul(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
| Subject: | Re: [HACKERS] Runtime Partition Pruning |
| Date: | 2018-01-04 23:58:24 |
| Message-ID: | CAKJS1f-7HrcvzDtEC8cCB-8FbmSWT-21AEzsXhvq0N-wzvAVvQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 5 January 2018 at 05:37, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> I tried this patch (applying it on Amit's last current version on top of
> 4e2970f8807f which is the latest it applies to) and regression tests
> fail with the attached diff; in all cases it appears to be an off-by-one
> in row count. Would you please give it a look?
Looks like it's down to ExplainPropertyFloat() having
machine-dependent behaviour.
On the machine that I was working with when testing this the following
code outputs "1"
#include <stdio.h>
double nfiltered = 1.0;
double nloops = 2.0;
int main(void)
{
printf("%.*f", 0, nfiltered / nloops);
return 0;
}
but on your machine it must be outputting "0"?
I'm not sure if I should just try to have even row numbers in the
tests, or if we should be fixing EXPLAIN so it is consistent.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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