| Lists: | pgsql-hackers |
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| From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
|---|---|
| To: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | float value is rounded |
| Date: | 2009-11-25 18:21:06 |
| Message-ID: | 162867790911251021w497da616r53b0a46002249117@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hello
I was surprised with rounding relative not big value. Is it correct?
postgres=# select 499188.546875::real;
float4
────────
499189
(1 row)
regards
Pavel Stehule
| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: float value is rounded |
| Date: | 2009-11-25 18:39:49 |
| Message-ID: | 22820.1259174389@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
> I was surprised with rounding relative not big value. Is it correct?
You do realize float4 has only 6 decimal digits of precision?
regards, tom lane
| From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: float value is rounded |
| Date: | 2009-11-25 18:46:11 |
| Message-ID: | 162867790911251046v769db287s67b5edd0061ea913@mail.gmail.com |
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| Lists: | pgsql-hackers |
2009/11/25 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
>> I was surprised with rounding relative not big value. Is it correct?
>
> You do realize float4 has only 6 decimal digits of precision?
>
To today I though so float4 is more practical :).
I am smarter now
Pavel
> regards, tom lane
>
| From: | David Fetter <david(at)fetter(dot)org> |
|---|---|
| To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: float value is rounded |
| Date: | 2009-11-26 00:32:04 |
| Message-ID: | 20091126003204.GA13542@fetter.org |
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| Lists: | pgsql-hackers |
On Wed, Nov 25, 2009 at 07:46:11PM +0100, Pavel Stehule wrote:
> 2009/11/25 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> > Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
> >> I was surprised with rounding relative not big value. Is it
> >> correct?
> >
> > You do realize float4 has only 6 decimal digits of precision?
> >
>
> To today I though so float4 is more practical :).
Floats have never been safe with respect to operations like =, and
won't become so.
Cheers,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
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