Обсуждение: BUG #4007: chr(0) doesn't work anymore

The following bug has been logged online:

Bug reference:      4007
Logged by:          Steve Clark
Email address:      sclark@netwolves.com
PostgreSQL version: 8.3.0
Operating system:   FreeBSD 6.2
Description:        chr(0) doesn't work anymore
Details:

Until 8.3.0 the following worked:
SELECT coalesce(param_value,chr(0)) from t_system_params where  param_name =
'default_unit_key';

it now fails with:
ERROR:  null character not permitted

The documentation says:
For other multibyte encodings the argument must designate a strictly ASCII
character.

NUL = 0 is a valid ascii character.

"Steve Clark" <sclark@netwolves.com> writes:
> Until 8.3.0 the following worked:
> SELECT coalesce(param_value,chr(0)) from t_system_params where  param_name =
> 'default_unit_key';

It would have "worked" only for rather small values of "work", since
most of the support for type TEXT isn't null-safe.  Try something like
"select chr(0) || 'foo';" for example.  Wouldn't an empty string do what
you want better?

> it now fails with:
> ERROR:  null character not permitted

This is an intentional change and won't be undone, at least not until
TEXT is null-safe, which isn't likely to happen in the foreseeable future.

            regards, tom lane

Tom Lane wrote:
> "Steve Clark" <sclark@netwolves.com> writes:
>
>>Until 8.3.0 the following worked:
>>SELECT coalesce(param_value,chr(0)) from t_system_params where  param_name =
>>'default_unit_key';
>
>
> It would have "worked" only for rather small values of "work", since
> most of the support for type TEXT isn't null-safe.  Try something like
> "select chr(0) || 'foo';" for example.  Wouldn't an empty string do what
> you want better?
>
>
>>it now fails with:
>>ERROR:  null character not permitted
>
>
> This is an intentional change and won't be undone, at least not until
> TEXT is null-safe, which isn't likely to happen in the foreseeable future.
>
>             regards, tom lane
>
>
Hi Tom,

I'm not sure. This was written in 2001/2002 timeframe and I inherited
it. I am not even sure what he was
trying to accomplish.

I'm not sure I understand what you mean about TEXT being null-safe.
What are the issues, and why was
it supported for years and now abruptly changed.

All I know is the code used to work from 7.3.x up through 8.2.5 and
now it doesn't.

If it not going the made to work according to the documentation then
the documentation should be
fixed.

Steve

Steve Clark <sclark@netwolves.com> writes:
> I'm not sure I understand what you mean about TEXT being null-safe.
> What are the issues, and why was
> it supported for years and now abruptly changed.

It never was supported, we are simply plugging a hole that let you
create a text value that would be likely to malfunction in subsequent
use.

            regards, tom lane