Re: Improve documentation for current_setting function

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От Bruce Momjian
Тема Re: Improve documentation for current_setting function
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Msg-id 20190222202901.yxby73nb3rp27qvh@momjian.us
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Ответ на Re: Improve documentation for current_setting function  (Eugen Konkov <kes-kes@yandex.ru>)
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On Fri, Feb 22, 2019 at 11:43:54AM +0200, Eugen Konkov wrote:
> Hello Bruce,
> 
> > How do you like the attached patch, which clarifies this?
> 
> >>in which case a missing parameter returns
> >>!     NULL.
> 
> not  always. It can be NULL or empty string. It depends if the current
> session is new or after finished transaction which makes 'local' changes
> to setting
> 
> Take into account these steps: https://www.postgresql.org/message-id/15646-0d3caee9f6266f60%40postgresql.org

Yes, I saw that recent thread.

> From  my  user point of view. if the boot value before transaction was
> NULL then after transaction it MUST stay NULL and not empty string.
> 
> This  will  be  consistent with that if I open new parallel session it
> will return NULL.
> 
> Also I see NULL value (if setting was not defined) is useful.
> 
> 
> Also this:
> set_config( 'my.name', NULL )
> must  set 'my.name' to NULL or must issue warning about NULL is turned
> into empty string.
> 
> Personally  I  dislike  that  NULL  is converted to empty string. This
> looks ugly. =(

Understood.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +


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